Search

Significant advances have been achieved in recent years in Reversed Field Pinch (RFP) physics, both from the experimental and the theoretical point of view. The main theoretical advances are based on fully 3D nonlinear visco-resistive MHD simulations, which gained a deeper understanding of the RFP's magnetic self-organization. Improved confinement regimes have been explored with two different approaches in the RFP. The first is associated with the spontaneous topological bifurcation from a cylindrical to a helical magnetic equilibrium. Such equilibria are favored by high plasma current levels and are associated with the emergence of partially conserved magnetic flux surfaces, resulting in the onset of a transport barrier. A fundamental role in determining the improvement of the experimental results is played by advanced active feedback control systems for the control of MHD instabilities. The second approach is based on active control of the current profile, which can induce significant enhancements of the confinement properties. High confinement of fast particles has been also observed in RFP plasmas.

Delivery of substances into the inner ear via local routes is increasingly being used in clinical treatment. Studies have focused on methods to increase permeability through the round window membrane (RWM) and enhance drug diffusion into the inner ear. However, the clinical applications of those methods have been unclear and few studies have investigated the efficacy of methods in an inner ear injury model. Here, we employed the medium chain fatty acid caprate, a biologically safe, clinically applicable substance, to modulate tight junctions of the RWM. Intratympanic treatment of sodium caprate (SC) induced transient, but wider, gaps in intercellular spaces of the RWM epithelial layer and enhanced the perilymph and cochlear concentrations/uptake of dexamethasone. Importantly, dexamethasone co–administered with SC led to significantly more rapid recovery from noise-induced hearing loss at 4 and 8 kHz, compared with the dexamethasone-only group. Taken together, our data indicate that junctional modulation of the RWM by SC enhances dexamethasone uptake into the inner ear, thereby hastening the recovery of hearing sensitivity after noise trauma.

Mobile ad hoc network is collection of wireless mobile nodes that are communicating each other without needed any backbone, access point. Mobile nodes change the Mobility frequently due to dynamic nature of MANET. Mobile node is an autonomous node is communicating each other using different wireless ad hoc network routing protocols. The comparison performance was made by small networks on CBR application apply from source node to destination nodes. The mobility model used was Random Way Point Model for randomly nodes placement because dynamic nodes change frequently every node was set randomly. In this article compare the various wireless routing protocols are Ad-hoc On demand Distance Vector, Dynamic Source Routing, Dynamic MANET on demand Routing and Zone Routing Protocol in ad-hoc networks. The performances analysis and evaluate is done performance metrics such as Average Jitter, Throughput, Average End to End delay, Packet Delivery Ratio on CBR traffic load. This simulation works done by Qualnet 5.0.2 simulator tools.

JT-60SA is the satellite tokamak under construction in Naka, Japan, in the framework of the EU-JA -Broader Approach? Agreement. In JT-60SA, to attain steady-state high-beta plasmas, suppression of Resistive Wall Modes (RWM) is necessary. At this purpose, a passive stabilizing plate (SP) and an active control system based on 18 in-vessel sector coils (SC) are foreseen. In the past years, physics studies have been carried out to produce the inputs for the design of the RWM control system and the SC design evolved accordingly. In the present arrangement, the coils are placed on the plasma side of SP, to minimize the magnetic shielding effects of passive structures. Electromagnetic analyses on SC have been carried out in support to the evaluation of the different coil design solutions and to derive the requirements for the related power supply system (RWM-PS). To achieve the highest flexibility in RWM control, it has been devised to feed each SC independently, with currents following 18 real-time references. In 2012, the SC design has been further improved by increasing the number of turns from 2 to 8. This allowed reducing the rated current, thus the voltage drops on the feeders and the power required from RWM-PS. To keep the RWM under control with relatively low Ampere-turns (2.2 kAt), the RWM-PS has to guarantee very fast dynamics (current bandwidth: 3 kHz; maximum latency: 50 us), largely beyond that of standard industrial applications. This paper firstly reports the main requirements for the RWM control system. Then, the reference design of the RWM-PS is described. It includes an ac/dc conversion system, dc-link capacitor banks and a set of 18 fast inverters. The advantages of the proposed scheme are discussed and the main electrical parameters are shown in detail. The main requirements of the control section are given, with details on possible implementation and interfaces with JT-60SA central control.

This thesis represents the summary of the research activities carried out during a three-years Ph.D. project. The work is divided into two parts, with the common feature of investigating the physical properties related to stability and control of Magneto-Hydro-Dynamic modes in fusion relevant plasmas. One of the aims of the work is to better understand the interaction between such plasmas and a wide range of 3-dimensional electro-magnetic boundary conditions. This part of the research has been carried out on the RFX-mod device, where advanced control strategies have been developed thanks to its state-of-the-art magnetic feedback system. A variety of interlaced problems have been addressed, starting with the improvement of the vacuum magnetic field spectrum through actuator-sensor decoupling, compensation of broken or deactivated coils with simple and real-time applicable strategies and multi-modal Resistive Wall Mode control with varying coil number and geometry. This has allowed to develop relevant control optimization techniques and knowledge for both the Reversed Field Pinch and Tokamak configurations. The former is an excellent playground for RWM studies, given the instability spectrum that is naturally developing. For the latter configuration instead, RWM stability is considered to be one major milestone to be achieved along the road to a commercial fusion reactor. The second part of the work is dedicated to this issue, and deals with the stability properties of Advanced Tokamak scenarios, with reference to the JT-60SA experiment in particular. Studies to understand RWM physics in high beta plasmas, where fluid rotation profiles and hot ions populations from Neutral Beams can play an important role, have been carried out with the MARS-F/K linear MHD codes. If detailed physics such as kinetic effects is coupled to a simplified description of the passive/active structures on one side, on the other hand a simplified plasma can be coupled to a complex 3-D model of the structures to assess realistic active control capabilities of a given system. Different tools are used and described for studying RWM damping physics, and to five a proof-of-principle for feedback control of such instabilities in Advanced Tokamak plasmas operating beyond the no-wall pressure limit.

In the framework of EU – JA “Broader Approach” Agreement, the JT-60SA satellite tokamak will be built in Naka, Japan. In JT-60SA, to achieve the steady-state high beta plasma, suppression of Resistive Wall Modes (RWM) is necessary. Therefore, a passive stabilizing plate and a RWM active control system based on in-vessel coils are foreseen for JT-60SA. In the present design, this system consists in 18 sector coils, 6 in the toroidal, 3 in the poloidal direction, rated for a maximum current of 2.5 kA and fed by a dedicated fast power supply system. The coils shall produce sufficient radial magnetic field at the plasma edge, and the active control system shall be fast enough to react in real time to the plasma instabilities. In addition, during fast transients of the plasma current, significant loop voltage could be induced along the sector coils, which could result in over-currents in the coils and in the power supplies. This paper deals with the electromagnetic analyses on the sector coils of JT-60SA, with the main aim to determine the voltage/current characteristic of the coils and, at the same time, to have a first estimation of amplitude and shape of the produced magnetic field; different sector coil design solutions were considered and evaluated. The studies on the coil over-currents during plasma disruption or vertical displacement events are also presented. The results give useful indications in support to the development of the sector coils and power supply design and the identification of their electrical and functional requirements.

The theoretical studies on the Resistive Wall Modes (RWM) and non-resonant Fishbone-Like External kink Mode (FLEM) in Reversed Field Pinch (RFP) plasmas are reported, and comparison is made with the Tokamaks. Various features of these two instabilities in the RFP and Tokamak configurations are investigated in order to provide an in-depth understanding on the mode physics. The toroidal MHD-kinetic hybrid stability code MARS-K was applied to the studies, which takes into account the drift kinetic effects of thermal particles as well as the isotropic/anisotropic energetic particles (EPs). The RWM behaviour in the RFP plasmas with shaped cross section is investigated first, and it is found to be quite different from Tokamaks. Furthermore, the EPs effects on RWMs are studied in both RFP and Tokamak plasmas, considering both isotropic and anisotropic energetic ions (EIs). Besides the RWMs, this study also finds the triggering of the FLEM instability, which is driven by the precessional motion of energetic ions. FLEMs can coexist or couple with the RWMs, depending on the plasma parameters. The MARS-K code is also applied to the study of the RWM stability in the JT-60SA Tokamaks, and the preliminary results are provided.

A MANET is an interconnection of mobile devices by wireless links, which forms a dynamic topology. Routing protocols play a vital role in transmission of data across the network. The two major classifications of routing protocols are unipath and multipath. In this paper, we have evaluated the performance of a widely used on-demand multipath routing protocol called AOMDV. This protocol has been selected due to its edge over other protocols in various aspects, such as reducing delay, routing load etc. The evaluation of AOMDV protocol is carried out in terms of four scenario patterns such as RWM, RPGM, MGM, and GMM in two different traffic patterns such as CBR and TCP using NS2 and Bonn Motion.