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排序方式: 共有233条查询结果,搜索用时 15 毫秒
101.
Mobile ad hoc networks (MANET) are infrastructure-less networks, dynamically formed by an independent system of mobile nodes that are connected via wireless links. Because routing is performed by nodes with limited resources, load should be efficiently distributed through the network. Otherwise, heavily-loaded nodes may make up a bottleneck that lowers the network performances by congestion and larger delays. Regrettably, load-balancing is a critical deficiency in MANET shortest-path routing protocols, as nodes at the center of the network are much heavily-loaded than the others. Thus, we propose, in this paper, load-balancing mechanisms that push the traffic further from the center of the network. Basically, we provide novel routing metrics that take into account nodes degree of centrality, for both proactive and reactive routing protocols. Simulations show that the proposed mechanisms improve the load distribution and significantly enhance the network performances in terms of average delay and reliability. 相似文献
102.
Local minima of quadratic forms on convex cones 总被引:1,自引:0,他引:1
We study the local minima and the critical values of a quadratic form on the trace of a convex cone. This variational problem
leads to the development of a spectral theory that combines matrix algebra and facial analysis of convex cones.
相似文献
103.
Romdhani Imed Kellil Mounir Lach Hong-Yon Bouabdallah Abdelmadjid Bettahar Hatem 《Communications Surveys & Tutorials, IEEE》2004,6(1):18-41
This article outlines the challenges of IP multicast over Mobile IP. Then it provides a comprehensive overview of existing multicast solutions to handle mobile sources and receivers in both the Mobile IPv4 and the Mobile IPv6 environments. The solutions are classified into different classes in light of how the network infrastructure is used and the nature of the multicast members (receivers or sources). For each solution, we present a brief overview; we describe the architecture and the proposed protocol; we discuss the advantages and the limitations; and we compare qualitatively all the solutions of each class based on common criteria such as optimal routing, join latency, handover transparency, etc. 相似文献
104.
Blanco P Polyakov P Bou-Ali MM Wiegand S 《The journal of physical chemistry. B》2008,112(28):8340-8345
In the present work we studied the thermal diffusion behavior of n-decane in various alkanes by thermogravitational column (TC) technique and the thermal diffusion forced Rayleigh scattering (TDFRS) method. The investigated lighter alkanes compared to n-decane are n-pentane, n-hexane, n-heptane, n-octane, and the heavier ones are n-tetradecane, n-pentadecane, n-hexadecane, n-heptadecane, n-octadecane, and n-eicosane. The binary mixture n-decane/ n-pentane we investigated at several different concentrations; all other mixtures were only investigated at a mass fraction of 50%. Even for the volatile n-pentane/ n-decane mixture the deviations between the thermal diffusion coefficients determined by the different methods agreed within the error bars. Typically the agreement between the two methods was in the order of 5%. In comparison to recently published TC and TDFRS data we found deviations in the order of 30% up to 40%. We analyze and discuss the possible reasons for the discrepancies for the present and the past publications. 相似文献
105.
Faith Corbo Gaenzler Yun-Wei Zhang Mounir A.I. Salem Michael B. Smith 《Tetrahedron》2009,65(43):8781-5197
A general route to the A-B-C ring system of phenanthridone alkaloids is available by acylation of 2-oxa-zolone with a 2-butadienylbenzoic acid derivative, followed by an intramolecular Diels-Alder reaction and hydrolysis. 相似文献
106.
Mounir Laroussi 《Journal of Infrared, Millimeter and Terahertz Waves》1992,13(10):1557-1569
A magnetized plasma column is found to be a notch absorber of microwave radiation propagating in the extraordinary mode. Based on this fact, a compact tunable microwave filter is designed and tested successfully. The center frequency of the absorbed band can be varied by adjusting the background magnetic field stength. The 3dB bandwidth and amount of attenuation are functions of the plasma current. These characteristics offer a great tunability, often sought after in microwave devices. This filter can find applications in microwave measurement systems where filtering of unwanted harmonics and spurious signals can directly affect the accuracy and resolution of the measurements. 相似文献
107.
The paper proposes a method to calculate parameters of equivalent sources induced on printed circuit traces. These parameters will be obtained taking into account the combination of several approaches: the induction law when the trace size is small as compared to the wavelength of the disturbances, and transmission lines theory in the opposite case. Nevertheless, the confrontation with a more precise evaluation, obtained using the theory of diffraction by conductors, reveals that it is necessary to make corrections to the transmission lines theory, in particular, when evaluating the resonant frequencies and the amplitude of induced parasites at these frequencies. We will introduce special boundary conditions as well as radiation mechanisms. 相似文献
108.
M. GhribM. Gaidi N. KhedherT. Ghrib M. Ben SalemH. Ezzaouia 《Applied Surface Science》2011,257(9):3998-4003
In this paper we report detail investigation and correlation between micro-structural and optical properties of nanocrystalline silicon (nc-Si) deposited by plasma enhancement chemical vapor deposition (PECVD) on porous aluminum structure. The influence of the microstructure of the nc-Si thin films on their optical properties was investigated through an extensive characterization. The effect of anodisation currents on the microstructure of aluminum surface layer and nc-Si films was systematically studied by atomic force microscopy (AFM) and transmission electron microscopy (TEM), Raman spectroscopy and X-ray diffraction (XRD). The optical constants (n and k as a function of wavelength) of the films were obtained using variable angle spectroscopic ellipsometry (SE) in the UV-vis-NIR regions. The silicon layer (SL) was modeled as a mixture of void, crystalline silicon and aluminum using the Bruggeman approximation. Based on this full characterization, it is demonstrated that the optical characteristics of the films are directly correlated to their micro-structural properties. A very bright photoluminescence (PL) was obtained and find to depend on anodisation current. 相似文献
109.
110.
Dalenda Ben Issa Abdennaceur Kachouri Mounir Samet 《Analog Integrated Circuits and Signal Processing》2011,68(1):9-20
In this paper a new design of Ultra-Wide Band (UWB) generator is presented. This circuit is the most important block in multi-bands
transmitter architecture of UWB communication system. The proposed UWB generator is composed of multi-bands voltage controlled
oscillator (VCO), mixer and rectangular pulse generator which consist of ring oscillator, time delay and AND gate function.
The UWB generator is based on multiplying the rectangular pulse envelope to a continuous sinusoidal wave in order to generate
the UWB signal. This UWB generator circuit produces an output signal which is characterized by the bandwidth of 1600 MHz divided
into three sub-bands of 528 MHz, centered at frequencies of 3.432, 3.96, 4.488 GHz and the limited Power Spectral Density
(PSD) is −41.44 dBm/MHz. The maximum amplitude of UWB signal is 214 mV, the pulse is during of 3 ns and the pulse repetition
period (PRP) is 32 ns. The power consumption is approximately equal to 26 mW at a voltage supply of 2.5 V. This topology is
designed in CMOS 0.35 μm AMS process technology. 相似文献