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51.
A broadband wireless access system is a bi-directional broadband wireless system to fixed networks at millimeter-wave frequencies. The propagation environment at millimeter-wave frequencies is one of the major challenges in delivering broadband services to fixed subscribers. At such high frequencies the signal is attenuated by the obstacles in the radio path between the subscriber and the hub, such as buildings, trees and vehicles in the radio path between the subscriber and the hub.Link adaptation techniques such as adaptive modulation and error control coding have been applied to wireless communication systems to overcome the multipath fading experienced by the transmitted signal. Diversity has long been recognized as an effective technique for combating the effect of channel multipath fading. In this study, we investigate the outage probability improvements due to the employments of various combinations of adaptive modulation, adaptive coding, and diversity techniques in a broadband wireless access system. The results indicate that using adaptive modulation, coding, and maximal ratio combining (MRC) yields significant enhancements in outage probability of the system. 相似文献
52.
A simple examination of Internet traffic shows a wide mix of relevant and unwanted traffic. The latter is becoming increasingly harmful to network performance and service availability, while often consuming precious network and processing resources. Coordinated attacks, such as distributed denial-of-services (DDoS), large-scale scans, and worm outbreaks, occur in multiple networks simultaneously and become extremely difficult to detect using an individual detection engine. This paper presents the specification of a new orchestration-based approach to detect, and, as far as possible, to limit the actions of these coordinated attacks. Core to the proposal is a framework that coordinates the receiving of a multitude of alerts and events from detectors, evaluates this input to detect or prove the existence of anomalies, and consequently chooses the best action course. This framework is named Orchestration-oriented Anomaly Detection System (OADS). We also describe an OADS prototype implementation of the proposed infrastructure and analyze initial results obtained through experimentation with this prototype. 相似文献
53.
Houyem Abderrazak Faten Turki Fréderic Schoenstein Mohieddine Abdellaoui Noureddine Jouini 《Ceramics International》2013,39(5):5365-5372
Ti3SiC2 was elaborated by two different methods: (i) Spark plasma sintering of 5Ti/2SiC/C powders and (ii) mechanical alloying of powders followed by Spark plasma sintering. The results showed that mechanical alloying was not advantageous for pure Ti3SiC2 formation but it can significantly improve the density of the obtained bulk material via the particles refinement as well as the microhardness by increasing the TiC content. It was found that the relative density was increased up to 98.58% for the sintered mechanically alloyed sample whereas it was not more than 96.04% for the sintered 5Ti/2SiC/C starting powders. The Vickers microhardness measured for both bulk samples demonstrates a high improvement for the previously mechanically alloyed powder mixture, as it was of about 1282 Hv and only 581.2 Hv for the alloy obtained from 5Ti/2SiC/C starting powders. 相似文献
54.
Baligh Touati Abdelaziz Gassoumi Najoua Kamoun Turki 《Journal of Materials Science: Materials in Electronics》2017,28(24):18387-18395
The present work reports on the chemical synthesizes of (0–8 at.%) silver (Ag)-doped PbS thin films with tunable opto-electrical properties. From the X-ray diffraction analyses, it was understood that the preferred growth orientation of Ag:PbS films was dependent on the Ag doping concentration. The variation in the Ag:PbS films orientation was reflected in the film morphology as observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). SEM studies revealed that the variation in Ag concentration lead to different grain shapes for different grain orientations. The AFM study showed that the RMS roughness of the undoped PbS film has been reduced considerably due to silver doping. From the optical studies, a widening in the optical band gap was revealed after Ag-doping due to the quantum confinement effect. It was obtained that 4 at.% Ag-doped PbS thin films display an optimum band gap value of 1.45 eV. As for electrical characterization result, the resistivity reduces and the carrier density improved with 4 at.% Ag concentration. Based on all the data, it was concluded that the 4 at.% Ag-doped PbS thin film showed the best morphological, optical and electrical behavior, which recommend it as an active layer for solar cell devices. 相似文献
55.
Damian Giaouris Soumitro Banerjee Fotis Stergiopoulos Simira Papadopoulou Spyros Voutetakis Bashar Zahawi Volker Pickert Abdullah Abusorrah Mohammed Al Hindawi Yusuf Al‐Turki 《International Journal of Circuit Theory and Applications》2014,42(10):1080-1091
Interleaved boost converters (IBCs) are used when energy conversion is required at high current levels. Such converter systems may undergo various nonlinear phenomena which can affect their performance adversely. In this paper, we study an IBC and demonstrate the first instability through a Neimark–Sacker bifurcation, resulting in a torus. An analysis based on the calculation of the monodromy matrix reveals that the torus has a rather strange form as the complex Floquet multipliers that became unstable have a real value close to ?1. We show that further variation in a parameter can result in novel nonlinear phenomena where the torus itself folds and grazes a switching manifold, resulting in a ‘wobbling’ of the closed loop that represents the torus in discrete time. Numerical and analytical results validate our work. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
56.
57.
Ifigeneia Giakoumaki Natalie Pollock Turki Aljuaid Anthony J. Sannicandro Moussira Alameddine Euan Owen Ioanna Myrtziou Susan E. Ozanne Ioannis Kanakis Katarzyna Goljanek-Whysall Aphrodite Vasilaki 《International journal of molecular sciences》2022,23(15)
Sarcopenia is characterised by an age-related decrease in the number of muscle fibres and additional weakening of the remaining fibres, resulting in a reduction in muscle mass and function. Many studies associate poor maternal nutrition during gestation and/or lactation with altered skeletal muscle homeostasis in the offspring and the development of sarcopenia. The aim of this study was to determine whether the musculoskeletal physiology in offspring born to mouse dams fed a low-protein diet during pregnancy was altered and whether any physiological changes could be modulated by the nutritional protein content in early postnatal stages. Thy1-YFP female mice were fed ad libitum on either a normal (20%) or a low-protein (5%) diet. Newborn pups were cross-fostered to different lactating dams (maintained on a 20% or 5% diet) to generate three groups analysed at weaning (21 days): Normal-to-Normal (NN), Normal-to-Low (NL) and Low-to-Normal (LN). Further offspring were maintained ad libitum on the same diet as during lactation until 12 weeks of age, creating another three groups (NNN, NLL, LNN). Mice on a low protein diet postnatally (NL, NLL) exhibited a significant reduction in body and muscle weight persisting up to 12 weeks, unlike mice on a low protein diet only prenatally (LN, LNN). Muscle fibre size was reduced in mice from the NL but not LN group, showing recovery at 12 weeks of age. Muscle force was reduced in NLL mice, concomitant with changes in the NMJ site and changes in atrophy-related and myosin genes. In addition, μCT scans of mouse tibiae at 12 weeks of age revealed changes in bone mass and morphology, resulting in a higher bone mass in the NLL group than the control NNN group. Finally, changes in the expression of miR-133 in the muscle of NLL mice suggest a regulatory role for this microRNA in muscle development in response to postnatal diet changes. Overall, this data shows that a low maternal protein diet and early postnatal life low-protein intake in mice can impact skeletal muscle physiology and function in early life while postnatal low protein diet favours bone integrity in adulthood. 相似文献
58.
Hadil M. Alahdal Sumya Ayad Abdullrezzaq Hawraz Ibrahim M. Amin Sitah F. Alanazi Abduladheem Turki Jalil Mehrdad Khatami Marwan Mahmood Saleh 《IET nanobiotechnology / IET》2023,17(1):22
Hyperthermia is an additional treatment method to radiation therapy/chemotherapy, which increases the survival rate of patients without side effects. Nowadays, Auroshell nanoparticles have attracted much attention due to their precise control over heat use for medical purposes. In this research, iron/gold Auroshell nanoparticles were synthesised using green nanotechnology approach. Auroshell gold@hematite nanoparticles were synthesised and characterised with rosemary extract in one step and the green synthesised nanoparticles were characterised by X‐ray powder diffraction, SEM, high‐resolution transmission electron microscopy, and X‐ray photoelectron spectroscopy analysis. Cytotoxicity of Auroshell iron@gold nanoparticles against normal HUVEC cells and glioblastoma cancer cells was evaluated by 2,5‐diphenyl‐2H‐tetrazolium bromide method, water bath hyperthermia, and combined method of water bath hyperthermia and nano‐therapy. Auroshell gold@hematite nanoparticles with minimal toxicity are safe against normal cells. The gold shell around the magnetic core of magnetite caused the environmental and cellular biocompatibility of these Auroshell nanoparticles. These magnetic nanoparticles with targeted control and transfer to the tumour tissue led to uniform heating of malignant tumours as the most efficient therapeutic agent. 相似文献
59.
Sadok Gaied Jean-Marc Roelandt Fabrice Pinard Francis Schmit Mikhael Balabane 《Journal of Materials Processing Technology》2009,209(1):387-395
A Tailor-Welded Blank (TWB) consists of steels of different thicknesses, strength types welded together to produce a single blank prior to the forming process. TWBs offer several notable benefits including decreased part weight, reduced manufacturing costs, increased environmental friendliness, and improved dimensional consistency. In order to take advantage of these benefits, however, designers need to overcome the formability of TWBs and be able to accurately predict unique characteristics related to TWB forming early in the design process. In this paper, a numerical model to predict the forming height dome and a specific forming curve of TWBs is presented. Finite element analyses of standard TWB forming tests (Nakazima) were performed in Arcelor Mittal Auto Application Research Center to determine the interaction between the weaker and the stronger materials. One of the most important aspects in the instability analysis is the problem of the measurement of the critical strain at necking. A new method is presented in this paper based on the analysis of the major strain rate using the discrete Gaussian convolution. A comparison of numerical and experimental results highlights a good agreement. The numerical approach offers a considerable gain to obtain specific FLC for all configurations. 相似文献
60.
The main contribution of this paper is the study of interpolation functions in control volume finite element method used
in equal order and applied to an incompressible two-dimensional fluid flow. Especially, the exponential interpolation function
expressed in the elemental local coordinate system is compared to the classic linear interpolation function expressed in the
global coordinate system. A quantitative comparison is achieved by the application of these two schemes to four flows that
we know the analytical solutions. These flows are classified in two groups: flows with privileged direction and flows without.
The two interpolation functions are applied to a triangular element of the domain then; a direct comparison of the results
given by each interpolation function to the exact value is easily realized. The two functions are also compared when used
to solve the discretized equations over the entire domain. Stability of the numerical process and accuracy of solutions are
compared.
Received: 20 October 2002 / Accepted: 2 December 2002 相似文献