827 research outputs found

    FCC structured ferromagnetic ultra-thin films with two spin layers described by fourth order perturbed Heisenberg Hamiltonian

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    Fourth order perturbation was applied to study a small variation of the azimuthal angle of spin of fcc structured ferromagnetic thin films with two spin layers. The variation of magnetic energy and the orientation of magnetic easy axis with the fourth order magnetic anisotropy constant in two spin layers was investigated. When the second order magnetic anisotropy constant at the top spin layer is higher than that of bottom spin layer, the total magnetic energy is slightly higher. Some spikes appeared in the 2D plot of of magnetic energy versus azimuthal angle of spin. According to the 3D plots, the peak value of the magnetic energy gradually decreases with the increase of the stress induced anisotropy constant, and thereafter the peak value of the magnetic energy gradually increases with the increase of the stress induced anisotropy constant. The angle between magnetic easy and hard directions was not 90 degrees. The magnetic easy and hard directions of the film with a higher second order magnetic anisotropy constant of top layer are different from the magnetic easy and hard directions of the film with a lower second order magnetic anisotropy constant of top layer. When the second order magnetic anisotropy constant of the bottom layer is increased, the total magnetic energy does not change

    Disaster-Resilient Control Plane Design and Mapping in Software-Defined Networks

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    Communication networks, such as core optical networks, heavily depend on their physical infrastructure, and hence they are vulnerable to man-made disasters, such as Electromagnetic Pulse (EMP) or Weapons of Mass Destruction (WMD) attacks, as well as to natural disasters. Large-scale disasters may cause huge data loss and connectivity disruption in these networks. As our dependence on network services increases, the need for novel survivability methods to mitigate the effects of disasters on communication networks becomes a major concern. Software-Defined Networking (SDN), by centralizing control logic and separating it from physical equipment, facilitates network programmability and opens up new ways to design disaster-resilient networks. On the other hand, to fully exploit the potential of SDN, along with data-plane survivability, we also need to design the control plane to be resilient enough to survive network failures caused by disasters. Several distributed SDN controller architectures have been proposed to mitigate the risks of overload and failure, but they are optimized for limited faults without addressing the extent of large-scale disaster failures. For disaster resiliency of the control plane, we propose to design it as a virtual network, which can be solved using Virtual Network Mapping techniques. We select appropriate mapping of the controllers over the physical network such that the connectivity among the controllers (controller-to-controller) and between the switches to the controllers (switch-to-controllers) is not compromised by physical infrastructure failures caused by disasters. We formally model this disaster-aware control-plane design and mapping problem, and demonstrate a significant reduction in the disruption of controller-to-controller and switch-to-controller communication channels using our approach.Comment: 6 page

    Synthesis, Spectroscopic Characterization of Cobalt ComplexfromC16H19N3O3S and photodegradation using prepared Nano TiO2catalyst

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    Coblatcomplex has been prepared by reaction between C16H19N3O3S (L) as ligand and metal salt (II). The prepared complex were characterized by infrared spectra, electromic spectra, magnetic susceptibility, molar conductivity measurement and metal analysis by atomic absorption and (C.H.N) analysis. From these studies tetrahedral geometry structure for the complex was suggested. The photodegredation of complex were study using photoreaction cell and preparednanoTiO2 catalyst in different conditions (concentration, temperatures, pH).The results show that the recation is of a first order with activation energy equal to (6.6512 kJ /mol)

    Protection of Galvanized steel from corrosion in salt media using sulfur nanoparticles

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    تم دراسة خصائص الكبريت النانوي بوساطة  جهاز مجهر القوة الذري. أظهرت قياسات مجهر القوة الذرية الحجم الكلي للكبريت النانوي المحضر بوساطة مزج ثايوسلفات الصوديوم مع مستخلص نبات  اليقطين مساويا 93.62نانومتر .تم دراسة حماية التاكل لمعدن الكلفانك ستيل  في الوسط الملحي وبمختلف درجات الحرارة بوساطة الكبريت النانوي وتم الحصول على افضل نتائج ثرموديناميكية  للمعدن بوجود الكبريت النانوي حيث كفاءة التثبيط ومقاومة لتاكل للمعدن تعطي اعلى قيمة عند اعلى درجة حرارية بوجود المثبط بلمقارنة بغيابة .كذلك سرعة التاكل تقل عند زيادة درجة الحرارة بوجود الكبريت النانوي, القيم الموجة للدالة الحرارية بوجود وبعدم وجود الكبريت النانوي تدل على انه التفاعل ماص للحرارة . لذا يقترح ان الكبريت النانوي مثبط جيد لمعدن الكالفانك ستيل في الوسط الملحي                The characteristics of sulfur nanoparticles were studied by using atomic force microscope (AFM) analysis. The atomic force microscope (AFM) measurements showed that the average size of sulfur nanoparticles synthesized using thiosulfate sodium solution through the extract of cucurbita pepo extra was 93.62 nm. Protecting galvanized steel from corrosion in salt media was achieved by using sulfur nanoparticles in different temperatures. The obtained data of thermodynamic in the presence of sulfur nanoparticles referred to high value as compares to counterpart in the absence of sulfur nanoparticles, the high inhibition efficiency (%IE) and corrosion resistance were at high temperature, the corrosion rate or weight loss decreased with increasing temperature in the presence of sulfur nanoparticles. The positive value of enthalpy ∆H* for galvanized steel with and without sulfur nanoparticles indicates that the reaction was endothermic. Therefore, the sulfur nanoparticles can be suggested as good inhibitor for galvanization in salt media