On the barrier-resilience of arrangements of ray-sensors

Given an arrangement A of n sensors and two points s and t in the plane, the barrier resilience of A with respect to s and t is the minimum number of sensors whose removal permits a path from s to t such that the path does not intersect the coverage region of any sensor in A. When the surveillance domain is the entire plane and sensor coverage regions are unit line segments, even with restricted orientations, the problem of determining the barrier resilience is known to be NP-hard. On the other hand, if sensor coverage regions are arbitrary lines, the problem has a trivial linear time solution. In this paper, we give an O(n2m) time algorithm for computing the barrier resilience when each sensor coverage region is an arbitrary ray, where m is the number of sensor intersections.Natural Sciences and Engineering Research Council of Canad

Minimum Cell Connection in Line Segment Arrangements

We study the complexity of the following cell connection problems in segment arrangements. Given a set of straight-line segments in the plane and two points a and b in different cells of the induced arrangement: [(i)] compute the minimum number of segments one needs to remove so that there is a path connecting a to b that does not intersect any of the remaining segments; [(ii)] compute the minimum number of segments one needs to remove so that the arrangement induced by the remaining segments has a single cell. We show that problems (i) and (ii) are NP-hard and discuss some special, tractable cases. Most notably, we provide a near-linear-time algorithm for a variant of problem (i) where the path connecting a to b must stay inside a given polygon P with a constant number of holes, the segments are contained in P, and the endpoints of the segments are on the boundary of P. The approach for this latter result uses homotopy of paths to group the segments into clusters with the property that either all segments in a cluster or none participate in an optimal solution

Metal silicide/poly-Si Schottky diodes for uncooled microbolometers

Nickel silicide Schottky diodes formed on polycrystalline Si films are proposed as temperature sensors of monolithic uncooled microbolometer IR focal plane arrays. Structure and composition of nickel silicide/polycrystalline silicon films synthesized in a low-temperature process are examined by means of transmission electron microscopy. The Ni silicide is identified as multi-phase compound composed by 20 to 40% of Ni3Si, 30 to 60% of Ni2Si and 10 to 30% of NiSi with probable minor content of NiSi2 at the silicide/poly-Si interface. Rectification ratios of the Schottky diodes vary from ~100 to ~20 for the temperature increasing from 22 to 70C; they exceed 1000 at 80K. A barrier of ~0.95 eV is found to control the photovoltage spectra at room temperature. A set of barriers is observed in photo-emf spectra at 80K and attributed to the Ni-silicide/poly-Si interface. Absolute values of temperature coefficients of voltage and current are found to vary from 0.3 to 0.6%/K for forward biasing and around 2.5%/K for reverse biasing of the diodes.Comment: 18 pages, 7 figure

Application of remote sensors in coastal zone observations

A review of processes taking place along coastlines and their biological consideration led to the determination of the elements which are required in the study of coastal structures and which are needed for better utilization of the resources from the oceans. The processes considered include waves, currents, and their influence on the erosion of coastal structures. Biological considerations include coastal fisheries, estuaries, and tidal marshes. Various remote sensors were analyzed for the information which they can provide and sites were proposed where a general ocean-observation plan could be tested

Barrier Graphs and Extremal Questions on Line, Ray, Segment, and Hyperplane Sensor Networks

A sensor network is typically modeled as a collection of spatially distributed objects with the same shape, generally for the purpose of surveilling or protecting areas and locations. In this dissertation we address several questions relating to sensors with linear shapes: line, line segment, and rays in the plane, and hyperplanes in higher dimensions. First we explore ray sensor networks in the plane, whose resilience is the number of sensors that must be crossed by an agent traveling between two known locations. The coverage of such a network is described by a particular tripartite graph, the barrier graph of the network. We show that barrier graphs are perfect (Berge) graphs and have a rigid neighborhood structure due to the rays\u27 geometry. We introduce two extremal problems for networks in the plane made of line sensors, line segment sensors, or ray sensors, which informally ask how well it is possible to simultaneously protect k locations with n (line/ray/segment)-shaped sensors from intruders. The first question allows any number of intruders, while the second assumes there is a lone intruder. We show these are questions to be answered separately, and provide complete answers for k = 2 in both cases. We provide asymptotically tight answers for question (1) when k = 3, 4 and the locations are in convex position. We also provide asymptotic lower bounds for question (1) for any k. Finally, we generalize these extremal problems to d dimensions. For the d-dimensional version of question (1) we provide asymptotic lower and upper bounds for any combination of k and d, though these bounds do not meet

Preparation and Characterisation of High Aspect Ratio Materials for Bone Tissue Engineering

This research work aims to give an overview of the synthesis of high aspect ratio materials for bone tissue engineering. The work was carried out using high aspect materials of both natural (micro fibrillated cellulose from jute, spider silk, cocoon silk) and synthetic grade (MgO and ZnO nanorods). Micro fibrillated cellulose was extracted from jute by washing it thoroughly with sodium hydroxide and bleaching it with hydrogen peroxide followed by acid hydrolysis with sulphuric acid. Spidroin was extracted from spider silk using different benign solvents and fibroin was extracted from Bombyx mori following the lithium bromide standard protocol. Hydrothermal method was followed for synthesis of magnesium oxide and zinc oxide nanorods. Micro fibrillated cellulose was characterized by SEM, XRD, FTIR, DSC, TGA, dispersion studies, and phytochemical tests. Spidroin and fibroin was analyzed using Fluorescence microscopy, FTIR, and CD. Magnesium oxide and zinc oxide nanorods were characterized using SEM, and XRD. Also, a comparative in-vitro cytotoxicity of all these materials was checked using adipose derived stem cells (ADSCs). From the SEM results it was found that the cellulose extracted from jute were micro fibrillated. The FTIR and XRD data showed that cellulose type II was extracted. Also the degradation of cellulose at 270 °C was confirmed from TGA results. Both spidroin and fibroin was successfully extracted using simple benign solvents. FTIR and CD data showed the presence of good amount of ß-sheets. FESEM of both MgO and ZnO showed that the nanoparticles agglomerated together to form nanorod like structure. The MTT study revealed that spider silk was more compatible followed by cocoon silk, cellulose, MgO and ZnO. This concludes that while both the high aspect ratio as well as the biocompatibility of the materials is an important factor designing materials for load bearing application

Role of ambient air on photoluminescence and electrical conductivity of assembly of ZnO Nanoparticles

Effect of ambient gases on photoluminescence (PL) and electrical conductivity of films prepared using ZnO nanoparticles (NPs) have been investigated. It is observed that NPs of size below 20 nm kept inside a chamber exhibit complete reduction in their visible PL when oxygen partial pressure of the surrounding gases is decreased by evacuation. However the visible PL from ZnO NPs is insensitive to other major gases present in the ambient air. The rate of change of PL intensity with pressure is inversely proportional to the ambient air pressure and increases when particle size decreases due to the enhanced surface to volume ratio. On the other hand an assembly of ZnO NPs behaves as a complete insulator in the presence of dry air and its major components like N2, O2 and CO2. Electrical conduction having resistivity ~102 - 103 {\Omega}m is observed in the presence of humid air. The depletion layer formed at the NP surface after acquiring donor electrons of ZnO by the adsorbed oxygen, has been found to control the visible PL and increases the contact potential barrier between the NPs which in turn enhances the resistance of the film.Comment: arXiv admin note: significant text overlap with arXiv:1008.249