Predicting Performance of Channel Assignments in Wireless Mesh Networks through Statistical Interference Estimation

Wireless Mesh Network (WMN) deployments are poised to reduce the reliance on wired infrastructure especially with the advent of the multi-radio multi-channel (MRMC) WMN architecture. But the benefits that MRMC WMNs offer viz., augmented network capacity, uninterrupted connectivity and reduced latency, are depreciated by the detrimental effect of prevalent interference. Interference mitigation is thus a prime objective in WMN deployments. It is often accomplished through prudent channel allocation (CA) schemes which minimize the adverse impact of interference and enhance the network performance. However, a multitude of CA schemes have been proposed in research literature and absence of a CA performance prediction metric, which could aid in the selection of an efficient CA scheme for a given WMN, is often felt. In this work, we offer a fresh characterization of the interference endemic in wireless networks. We then propose a reliable CA performance prediction metric, which employs a statistical interference estimation approach. We carry out a rigorous quantitative assessment of the proposed metric by validating its CA performance predictions with experimental results, recorded from extensive simulations run on an ns-3 802.11g environment

Impact of Genetic Variation and Timescale on Diatom Salinity Stress Response

Natural environments are dynamic, and organisms must sense and respond to changing conditions. One common way organisms deal with stressful environments is through gene expression changes, allowing for stress acclimation and resistance which occurs over varying time spans in different species. The recent evolutionary history of populations could greatly influence their ability to respond successfully. An evolutionary history in disturbed or fluctuating conditions could promote increased resistance or a more rapid response to these environmental stressors. To understand the impact of genotypic variation and timescales on response and acclimation to salinity changes, we have been exploiting the abilities of euryhaline diatoms in the order Thalassiosirales. This dissertation explores the mechanisms two species of Thalassiosirales use to mitigate short- and long-term effects of salinity stress. We first clarified the phylogenetic relationships of Cyclotella, one of the largest clades in the order containing numerous marine—freshwater transitions, reclassifying the relatively new genus Spicaticribra as a member of Cyclotella based on phylogenetic analyses of the genes rbcL, psbC, SSU, and LSU. We then determined that variation derived from genotypic differences between strains of Cyclotella cryptica had a greater impact then that imposed by gene expression changes following acclimation to different salinity conditions. When pooled together, the primary transcriptome modifications were related to the regulation of compatible solutes and ion transporters in an effort to maintain the osmotic gradient in suboptimal salinities. Subsequently, we acclimated multiple strains of Skeletonema marinoi, another euryhaline member of Thalassiosirales, to a range of salinities. With sufficient technical replication of these strains, we were able to determine that the variation between strains was due largely to degree of differential expression of genes, rather than strains regulating different genes entirely. Including genetic variation allowed us to identify more genes impacted by salinity changes than any one strain would have revealed and, additionally, we found a small set of 27 shared genes that were differentially expressed in all strains. We argue that this core set may have played an important role in ancestral marine—freshwater transitions for S. marinoi. Similar to C. cryptica, averaged response across all strains relied heavily on long-term maintenance of the cellular osmotic gradient, but there was little other indication of severe stress in the salinity treatments we used. We found considerable disparity in comparing the results of our post-acclimated C. cryptica behavior with previously reported short-term stress behavior in the species. Thus, we conducted a short-term time series experiment looking at C. cryptica’s gene expression response to a rapid exposure to freshwater. Differential gene expression analysis concluded C. cryptica responds to freshwater shock by temporarily halting growth and downregulating genes associated with maintenance of cellular division, such as ribosome biogenesis, transcription, and translation. Genes involved in reactive oxygen species scavenging and regulation of the osmotic gradient (i.e., osmolytes and ion transporters) are upregulated. Although limited, our comparison of results from different timescales found little overlap between the regulated genes during the peak period of stress, initial acclimation, and post-acclimation. This suggests that there is wide variation in the genes responsible for various stages of the stress response. These experiments highlight the power of including genetic variation to uncover mechanisms utilized in environmental stress response, as well as the importance of considering how that response changes from exposure to acclimation in order to develop a complete picture of how organisms cope with stress

Lifting the Veil: The Face of TFP in an Indian Rail Mill

We use a proprietary data set on the floor-level operations at the Bhilai Rail and Structural Mill (RSM) in India to understand how output rose sharply in response to competitive pressures. Output increases came predominantly from reductions in production delays of various kinds. We model interruptions to the production process as a function of worker characteristics and training and find that a large part of the avoidable delay reductions are attributable to a particular form of training, suggesting that such investments can have very high returns. Our work suggests very high returns to knowledge-enhancing investments in emerging economies.Total Factor Productivity (TFP), plant level data, competitiveness and trade

Reliable Prediction of Channel Assignment Performance in Wireless Mesh Networks

The advancements in wireless mesh networks (WMN), and the surge in multi-radio multi-channel (MRMC) WMN deployments have spawned a multitude of network performance issues. These issues are intricately linked to the adverse impact of endemic interference. Thus, interference mitigation is a primary design objective in WMNs. Interference alleviation is often effected through efficient channel allocation (CA) schemes which fully utilize the potential of MRMC environment and also restrain the detrimental impact of interference. However, numerous CA schemes have been proposed in research literature and there is a lack of CA performance prediction techniques which could assist in choosing a suitable CA for a given WMN. In this work, we propose a reliable interference estimation and CA performance prediction approach. We demonstrate its efficacy by substantiating the CA performance predictions for a given WMN with experimental data obtained through rigorous simulations on an ns-3 802.11g environment.Comment: Accepted in ICACCI-201

Radio Co-location Aware Channel Assignments for Interference Mitigation in Wireless Mesh Networks

Designing high performance channel assignment schemes to harness the potential of multi-radio multi-channel deployments in wireless mesh networks (WMNs) is an active research domain. A pragmatic channel assignment approach strives to maximize network capacity by restraining the endemic interference and mitigating its adverse impact on network performance. Interference prevalent in WMNs is multi-faceted, radio co-location interference (RCI) being a crucial aspect that is seldom addressed in research endeavors. In this effort, we propose a set of intelligent channel assignment algorithms, which focus primarily on alleviating the RCI. These graph theoretic schemes are structurally inspired by the spatio-statistical characteristics of interference. We present the theoretical design foundations for each of the proposed algorithms, and demonstrate their potential to significantly enhance network capacity in comparison to some well-known existing schemes. We also demonstrate the adverse impact of radio co- location interference on the network, and the efficacy of the proposed schemes in successfully mitigating it. The experimental results to validate the proposed theoretical notions were obtained by running an exhaustive set of ns-3 simulations in IEEE 802.11g/n environments.Comment: Accepted @ ICACCI-201

Restore the natural: a review and case series report on reattachment

Reattachment of the original tooth fragment to the fractured tooth helps in maintaining the tooth's color, wear resistance, morphology and translucency in the restoration. This article describes the reattachment of fractured fragment using a fiber post and dual cure resin cement with a self-etching adhesive. Two young male patients reported with a complicated crown fracture of the right maxillary central incisor due a road traffic accident. The fractured fragments were loosely attached to the palatal gingival tissue, which was then surgically removed and preserved for the reattachment procedure. The fractured tooth segments were successfully reattached following fiber post cementation. Tooth fragment reattachment procedure offers ultraconservative, safe, fast and esthetically pleasing results when the fractured fragment is available due to the improvement of adhesive techniques and restorative materials. Fiber reinforced resins not only allows creation of esthetic restoration but also the preservation and reinforcement of tooth structure. At the 18months follow-up, the resultant appearance was acceptable to the patient

Mechanics and force transmission in soft composites of rods in elastic gels

We report detailed theoretical investigations of the micro-mechanics and bulk elastic properties of composites consisting of randomly distributed stiff fibers embedded in an elastic matrix in two and three dimensions. Recent experiments published in Physical Review Letters [102, 188303 (2009)] have suggested that the inclusion of stiff microtubules in a softer, nearly incompressible biopolymer matrix can lead to emergent compressibility. This can be understood in terms of the enhancement of the compressibility of the composite relative to its shear compliance as a result of the addition of stiff rod-like inclusions. We show that the Poisson's ratio $\nu$ of such a composite evolves with increasing rod density towards a particular value, or {\em fixed point}, independent of the material properties of the matrix, so long as it has a finite initial compressibility. This fixed point is $\nu=1/4$ in three dimensions and $\nu=1/3$ in two dimensions. Our results suggest an important role for stiff filaments such as microtubules and stress fibers in cell mechanics. At the same time, our work has a wider elasticity context, with potential applications to composite elastic media with a wide separation of scales in stiffness of its constituents such as carbon nanotube-polymer composites, which have been shown to have highly tunable mechanics.Comment: 10 pages, 8 figure

Chemo Assisted Magnetic Abrasive Finishing: Experimental Investigations

AbstractIn modern industries with advancement of technology advanced engineering materials are needed to be used like Tungsten, Titanium alloys, ceramics, various composites etc. These materials possess some special characteristics such as high hardness, high wear resistance, high toughness, high strength etc. which make them preferred over conventional materials in modern industries. Due to the stringent properties these materials are difficult to process. Different conventional finishing processes like grinding, lapping, honing, buffing etc. are generally inefficient in finishing these materials. Although processes like abrasive flow machining, magnetic field assisted finishing processes and chemo-mechanical finishing may be used but these may be less productive. Therefore a new process which uses combination of chemical oxidation and magnetic field assisted abrasion (magnetic abrasive finishing) has been conceived in the present work for faster processing.To establish the process experiments have been conducted on tungsten work piece and the effects of various process parameters like percentage weight of abrasive, oxidizing agent concentration, rotational speed of magnet and working gap on process response namely percentage change in average surface roughness value (ΔRa) was recorded. The experiments were planned using Taguchi L9 orthogonal array. Experimental data was analyzed using analysis of variance to understand contribution of various process factors on process response. SEM micrographs have also been obtained to study the surface morphology of the finished work piece. Regression model was developed to predict the percentage change in surface roughness in terms of significant process factors

Population study of Pyxis arachnoides brygooi (Vuillemin & Domergue, 1972) in the area surrounding the Village des Tortues, Ifaty-Mangily, southwest Madagascar

The Madagascar spider tortoise (Pyxis arachnoides spp.) is faced with the threat of habitat destruction as well as the international pet trade. Habitat requirements and population structure of this species are largely unknown. Detailed studies have so far concentrated on the subspecies Pyxis arachnoides arachnoides. The present study surveyed a population of the western subspecies Pyxis arachnoides brygooi during the wet season from February to April 2008. The survey was carried out in the forest of Ifaty - Mangily, 20 km north of Toliara, and supported by a local tortoise centre, the Village des Tortues. Population densities were estimated from transect counts and plot surveys; they range from 0.33 to 1.72 animals per hectare. Both sexes were evenly represented in the field during the research period. Three individuals of the subspecies Pyxis arachnoides arachnoides were detected during this field survey. Their presence might be due to a transitional zone of both subspecies in the area of research. RÉSUMÉLa tortue araignée de Madagascar, Pyxis arachnoides spp. est menacée par la destruction de son habitat naturel et par les collectes illicites de spécimens destinés au commerce. Les besoins écologiques et la structure de la population naturelle de cette espèce sont encore peu connus. Jusqu’à présent, la plupart des études effectuées se sont concentrées sur la sous - espèce nominative Pyxis arachnoides arachnoides. La présente étude a été réalisée dans la partie sud-ouest de Madagascar, dans la forêt d’Ifaty-Mangily, à 20 kilomètres au nord de Toliara pendant la saison humide, entre février et avril 2008 sur une population de Pyxis arachnoides brygooi. Les travaux sur le terrain ont été effectués en coopération avec le « Village des Tortues » qui est un centre d’élevage et de sauvegarde des tortues confisquées par les autorités malgaches. La densité de la population étudiée sur le terrain varie de 0,33 à 1,72 individus par hectare ; cette estimation a été faite en se basant sur le suivi par transects et de parcelles d’une superficie d’un hectare. Le sexe ratio de ces tortues était équilibré au cours de la période d’étude. Les tortues ayant une longueur de carapace inférieure à 90 mm ont été classées en tant que juvéniles ou sub-adultes dans la mesure où ces individus ont été difficiles à sexer. La taille des individus recensés pendant cette étude varie de 37 à 122 millimètres et les femelles étaient en moyenne plus lourdes que les mâles. La présence des trois individus de Pyxis arachnoides arachnoides recensés dans la zone de recherche pourrait résulter d’une zone de transition entre les différentes sous-espèces