Cloned Access Point Detection and Point Detection and Prevention Mechanism in IEEE 802.11 Wireless Mesh Networks

IEEE 802.11 Wireless Mesh Network (WMN) is an emerging low cost, decentralized community-based broadband technology, which is based on self-healing and multi-hop deployment of Access Points (APs), so that to increase the coverage area with maximum freedom to end-users to join or leave the network from anywhere anytime having low deployment and maintenance cost. Such kind of decentralized structure and multihop architecture increases its security vulnerabilities especially against the APs. One of such possible security attack is the placement of cloned AP to create serious performance degradation in IEEE 802.11 WMN. In this paper, we discuss the different security vulnerabilities of AP in IEEE 802.11 WMN along with possible research directions. We also propose a mutual cooperation mechanism between the multi-hop APs and serving gateway so that to detect and prevent the possibility of cloned AP. In this way the large scale exploitation of IEEE 802.11 WMN can be eliminated

Passive security threats and consequences in IEEE 802.11 wireless mesh networks

The Wireless Mesh Network (WMN) is ubiquitous emerging broadband wireless network. However, the open wireless medium, multi-hop multi-radio architecture and ad-hoc connectivity amongst end-users are such characteristics which increases the vulnerabilities of WMN towards many passive and active attacks. A secure network ensures the confidentiality, integrity and availability of wireless network. Integrity and availability is compromised by active attacks, while the confidentiality of end-users traffic is compromised by passive attacks. Passive attacks are silent in nature and do not harm the network traffic or normal network operations, therefore very difficult to detect. However, passive attacks lay down a foundation for later launching an active attack. In this article, we discuss the vulnerable features and possible passive threats in WMN along with current security mechanisms as well as future research directions. This article will serve as a baseline guide for the passive security threats and related issues in WMNs

Visual mental imagery during caloric vestibular stimulation.

We investigated high-resolution mental imagery and mental rotation, while the participants received caloric vestibular stimulation. High-resolution visual mental imagery tasks have been shown to activate early visual cortex, which is deactivated by vestibular input. Thus, wepredicted that vestibular stimulation would disrupt high-resolution mental imagery; this prediction was confirmed. In addition, mental rotationtasks have been shown to activate posterior parietal cortex, which is also engaged in the processing of vestibular stimulation. As predicted,we also found that mental rotation is impaired during vestibular stimulation. In contrast, such stimulation did not affect performance of alow-imagery control task. These data document previously unsuspected interactions between the vestibular system and the high-level visualsystem

Imagery-related eye movements in 3D space depend on individual differences in visual object imagery.

During recall of visual information people tend to move their eyes even though there is nothing to see. Previous studies indicated that such eye movements are related to the spatial location of previously seen items on 2D screens, but they also showed that eye movement behavior varies significantly across individuals. The reason for these differences remains unclear. In the present study we used immersive virtual reality to investigate how individual tendencies to process and represent visual information contribute to eye fixation patterns in visual imagery of previously inspected objects in three-dimensional (3D) space. We show that participants also look back to relevant locations when they are free to move in 3D space. Furthermore, we found that looking back to relevant locations depends on individual differences in visual object imagery abilities. We suggest that object visualizers rely less on spatial information because they tend to process and represent the visual information in terms of color and shape rather than in terms of spatial layout. This finding indicates that eye movements during imagery are subject to individual strategies, and the immersive setting in 3D space made individual differences more likely to unfold

Comparison of BES measurements of ion-scale turbulence with direct, gyrokinetic simulations of MAST L-mode plasmas

Observations of ion-scale (k_y*rho_i <= 1) density turbulence of relative amplitude dn_e/n_e <= 0.2% are available on the Mega Amp Spherical Tokamak (MAST) using a 2D (8 radial x 4 poloidal channel) imaging Beam Emission Spectroscopy (BES) diagnostic. Spatial and temporal characteristics of this turbulence, i.e., amplitudes, correlation times, radial and perpendicular correlation lengths and apparent phase velocities of the density contours, are determined by means of correlation analysis. For a low-density, L-mode discharge with strong equilibrium flow shear exhibiting an internal transport barrier (ITB) in the ion channel, the observed turbulence characteristics are compared with synthetic density turbulence data generated from global, non-linear, gyro-kinetic simulations using the particle-in-cell (PIC) code NEMORB. This validation exercise highlights the need to include increasingly sophisticated physics, e.g., kinetic treatment of trapped electrons, equilibrium flow shear and collisions, to reproduce most of the characteristics of the observed turbulence. Even so, significant discrepancies remain: an underprediction by the simulations of the turbulence amplituide and heat flux at plasma periphery and the finding that the correlation times of the numerically simulated turbulence are typically two orders of magnitude longer than those measured in MAST. Comparison of these correlation times with various linear timescales suggests that, while the measured turbulence is strong and may be `critically balanced', the simulated turbulence is weak.Comment: 27 pages, 11 figure

Charge dependence of neoclassical and turbulent transport of light impurities on MAST

Carbon and nitrogen impurity transport coefficients are determined from gas puff experiments carried out during repeat L-mode discharges on the Mega-Amp Spherical Tokamak (MAST) and compared against a previous analysis of helium impurity transport on MAST. The impurity density profiles are measured on the low-field side of the plasma, therefore this paper focuses on light impurities where the impact of poloidal asymmetries on impurity transport is predicted to be negligible. A weak screening of carbon and nitrogen is found in the plasma core, whereas the helium density profile is peaked over the entire plasma radius.Comment: 17 pages, 7 figure

Characterisation of the L-mode Scrape Off Layer in MAST: decay lengths

This work presents a detailed characterisation of the MAST Scrape Off Layer in L-mode. Scans in line averaged density, plasma current and toroidal magnetic field were performed. A comprehensive and integrated study of the SOL was allowed by the use of a wide range of diagnostics. In agreement with previous results, an increase of the line averaged density induced a broadening of the midplane density profile.Comment: 30 pages, 11 figure

Photoionization models of the CALIFA HII regions. I. Hybrid models

Photoionization models of HII regions require as input a description of the ionizing SED and of the gas distribution, in terms of ionization parameter U and chemical abundances (e.g. O/H and N/O). A strong degeneracy exists between the hardness of the SED and U, which in turn leads to high uncertainties in the determination of the other parameters, including abundances. One way to resolve the degeneracy is to fix one of the parameters using additional information. For each of the ~ 20000 sources of the CALIFA HII regions catalog, a grid of photoionization models is computed assuming the ionizing SED being described by the underlying stellar population obtained from spectral synthesis modeling. The ionizing SED is then defined as the sum of various stellar bursts of different ages and metallicities. This solves the degeneracy between the shape of the ionizing SED and U. The nebular metallicity (associated to O/H) is defined using the classical strong line method O3N2 (which gives to our models the status of "hybrids"). The remaining free parameters are the abundance ratio N/O and the ionization parameter U, which are determined by looking for the model fitting [NII]/Ha and [OIII]/Hb. The models are also selected to fit [OII]/Hb. This process leads to a set of ~ 3200 models that reproduce simultaneously the three observations. We find that the regions associated to young stellar bursts suffer leaking of the ionizing photons, the proportion of escaping photons having a median of 80\%. The set of photoionization models satisfactorily reproduces the electron temperature derived from the [OIII]4363/5007 line ratio. We determine new relations between the ionization parameter U and the [OII]/[OIII] or [SII]/[SIII] line ratios. New relations between N/O and O/H and between U and O/H are also determined. All the models are publicly available on the 3MdB database.Comment: Accepted for publication in A&

Changes in the facial soft tissue profile after maxillary orthognathic surgery

OBJECTIVES To compare the changes of the soft tissue profile in relation to the displacement of the underlying hard structures in maxillary orthognathic surgery and to contribute to the esthetic prediction of the facial profile after surgical procedures. MATERIALS AND METHODS We analyzed the sagittal changes in the facial soft tissue profile related to surgical changes in skeletal structures after maxillary osteotomy in a retrospective study. The study sample comprised 115 adult patients between the ages of 18-50 years who had undergone maxillary orthognathic surgery and interdisciplinary orthodontic treatment at the Department of Orthodontics, Ludwig-Maximilians University of Munich, Germany. LeFort I osteotomy cases in both maxillary monognathic and bignathic osteotomy procedures were included. All subjects had received rigid fixation. A cephalometric analysis of presurgical and postsurgical cephalograms was performed and the correlations between hard tissue and soft tissue change ratios were evaluated using a bivariate linear regression analysis. A vertical line through the landmark sella (S) perpendicular to the nasion-sella line (NSL) served as the reference plane. RESULTS The subnasale (Sn) followed the A point (A) by 57%, the soft tissue A point (A') followed the A point (A) by 73% and the upper lip, represented by the landmark labrale superius (Ls) followed the upper incisor (Is) by 73%; all three in a linear correlation with a mean prediction error of nearly 2 mm. CONCLUSION The scatterplots show a linear correlation with a wide spread for all three pairs of reference points. The wide spread and the high prediction error of almost 2 mm indicate low predictability of the expected lip position and Sn.ZUSAMMENFASSUNG ZIELE: Die Veränderungen des Weichgewebeprofils in Relation zur Verlagerung der darunter liegenden Hartgewebe durch maxilläre orthognathe Chirurgie zu vergleichen und einen Beitrag zur ästhetischen Prognose des Gesichtsprofils nach chirurgischen Maßnahmen zu leisten. MATERIAL UND METHODE In einer retrospektiven Studie analysierten wir die sagittalen Veränderungen des fazialen Weichgewebeprofils in Beziehung zu den chirurgischen Veränderungen der skelettalen Strukturen nach maxillärer Osteotomie. Die Studienprobe besteht aus 115 erwachsenen Patienten im Alter von 18–50 Jahren, die sich interdisziplinär maxillärer orthognather Chirurgie und kieferorthopädischer Therapie an der Poliklinik für Kieferorthopädie der Ludwig-Maximilians-Universität München unterzogen hatten. LeFort-I-Osteotomie-Fälle sowohl maxillärer monognather als auch bignather Osteotomieverfahren wurden in die Studie aufgenommen. Alle Patienten hatten eine starre Fixierung erhalten. Es wurde eine kephalometrische Analyse von präoperativen und postoperativen Fernröntgenseitenbildern durchgeführt, die Korrelationen zwischen Hart- und Weichgewebeveränderungen wurden mittels einer bivariaten linearen Regressionsanalyse ausgewertet. Als Referenzebene diente eine vertikale Linie durch den Referenzpunkt Sella (S), rechtwinklig zur Nasion-Sella-Linie (NSL). ERGEBNISSE Der Punkt Subnasale (Sn) folgte dem A\hbox-Punkt (A) um 57 %, der Weichgewebe-A-Punkt (A′) folgte dem A-Punkt (A) um 73 %, und die Oberlippe, repräsentiert durch den Referenzpunkt Labrale superius (Ls), folgte dem Inzision superius (Is) um 73 %, alle 3 in einer linearen Korrelation bei einer mittleren Abweichung von fast 2 mm. FAZIT Die Punktdiagramme zeigen eine lineare Korrelation mit einer breiten Streuung aller 3 Referenzpunktpaare. Die breite Streuung und die hohe mittlere Abweichung von fast 2 mm lassen auf eine schwache Vorhersagbarkeit der zu erwartenden Position von Oberlippe und Sn schließen