Distributed algorithms for barrier coverage using relocatable sensors

We study the barrier coverage problem using relocatable sensor nodes. We assume each sensor can sense an intruder or event inside its sensing range. Sensors are initially located at arbitrary positions on the barrier and can move along the barrier. The goal is to find final positions for sensors so that the entire barrier is covered. In recent years, the problem has been studied extensively in the centralized setting. In this paper, we study a barrier coverage problem in the distributed and discrete setting. We assume that we have n identical sensors located at grid positions on the barrier, and that each sensor repeatedly executes a Look-Compute-Move cycle: based on what it sees in its vicinity, it makes a decision on where to move, and moves to its next position. We make two strong but realistic restrictions on the capabilities of sensors: they have a constant visibility range and can move only a constant distance in every cycle. In this model, we give the first two distributed algorithms that achieve barrier coverage for a line segment barrier when there are enough nodes in the network to cover the entire barrier. Our algorithms are synchronous, and local in the sense that sensors make their decisions independently based only on what they see within their constant visibility range. One of our algorithms is oblivious whereas the other uses two bits of memory at each sensor to store the type of move made in the previous step. We show that our oblivious algorithm terminates within \(\varTheta (n^2)\) steps with the barrier fully covered, while the constant-memory algorithm is shown to take \(\varTheta (n)\) steps to terminate in the worst case. Since any algorithm in which a sensor can only move a constant distance in one step requires \(\varOmega (n)\) steps on some inputs, our second algorithm is asymptotically optimal.     

Optimization of ceramics bonding in the area of pressure sensor manufacturing

Ceramics joints are applied for producing products that should be made in a general shapes and dimensions for more advantageous usage. The article presents the research work related to ceramic joint quality evaluation, the thermal-structural analysis of ceramic joining and ceramic bond design and implementation. The role of ceramic material in the electronics industry and motivation for joining ceramics is described in the introduction. The requirements and methods for improving the quality of joints are summarized. Also, the results of simulations of pressure sensor cooling after removal from the oven during joining are discussed. The experimental results are evaluated by using a t-test before and after process cooling modification. Important directions for future research are summarized, with emphasis on the statistical determination of poor connection, and how the interface of modification of joint technology and process setting affects results and parameters that have been achieved.     

Optimal Sensor Networks for Area Monitoring Using Rotating and Beam Sensors

We consider the problem of monitoring the Euclidean plane using rotating sensors with detection sectors and beam sensors. We assume that intruders can appear anywhere at any time and move arbitrarily fast, and may have full knowledge of the sensor network. We require that such intruders be detected within a finite amount of time. We give an optimal network for this problem consisting of a combination of rotating sensors of angle 0 and beam sensors that uses the minimum number of both types of sensors. We show a trade-off between the density of beam sensors needed and the angle of the detection sector of the rotating sensors. Secondly, we give a family of sensor networks using only rotating sensors for the same problem, that demonstrate a trade-off between the detection time and the density of rotating sensors used. We show that the density of rotating sensors required in this case can be significantly reduced by increasing the angle of detection sectors. Finally, we show that our results on the infinite plane can be used to derive sensor networks that monitor some finite regions using a density of sensors that is asymptotically the same, or close to that of the infinite plane case.     

Scalable Realistic Rendering with Many‐Light Methods

Recent years have seen increasing attention and significant progress in many‐light rendering, a class of methods for efficient computation of global illumination. The many‐light formulation offers a unified mathematical framework for the problem reducing the full lighting transport simulation to the calculation of the direct illumination from many virtual light sources. These methods are unrivaled in their scalability: they are able to produce plausible images in a fraction of a second but also converge to the full solution over time. In this state‐of‐the‐art report, we give an easy‐to‐follow, introductory tutorial of the many‐light theory; provide a comprehensive, unified survey of the topic with a comparison of the main algorithms; discuss limitations regarding materials and light transport phenomena and present a vision to motivate and guide future research. We will cover both the fundamental concepts as well as improvements, extensions and applications of many‐light rendering.     

A new wavelet-based measure of image focus

We present a new measure of image focus. It is based on wavelet transform of the image and is defined as a ratio of high-pass band and low-pass band norms. We show this measure is monotonic with respect to the degree of defocusation and sufficiently robust. We experimentally illustrate its performance on simulated as well as real data and compare it with existing focus measures (gray-level variance and energy of Laplacian). Finally, an application of the new measure in astronomical imaging is shown.     

The mechanism of the oxidative polymerization of aniline and the formation of supramolecular polyaniline structures

Polyaniline is one of the most important conducting and responsive polymers. A molecular mechanism for the oxidation of aniline is proposed. This mechanism explains the specific features of aniline oligomerization and polymerization in various acidity ranges. The formation of polyaniline precipitates, colloids and thin films is reviewed and discussed on the basis of the chemistry of aniline oxidation. The generation of nanostructures, i.e. granules, nanotubes, nanowires and microspheres, is also considered. Oligomers containing phenazine constitutional units play an important role in self‐assembly to form templates. Polyaniline chains then grow from these templates and produce the various individual morphologies. Copyright © 2008 Society of Chemical Industry     

Control of polyaniline conductivity and contact angles by partial protonation

Many studies require a specific value of conductivity when investigating conducting polymers. The conductivity of polyaniline can efficiently be controlled by partial protonation of the polyaniline base. Although this is a simple task in principle, practical guidelines are missing. In the present study, the changes in the conductivity of polyaniline base after immersion in aqueous solutions of various acids are reported. Polyaniline base has been reprotonated in aqueous solutions of picric, camphorsulfonic and phosphoric acids. The conductivity of partially reprotonated polyaniline varied between 10⁻⁹ and 10⁰ S cm⁻¹. The relation between the pH of a phosphoric acid solution, which was in equilibrium with polyaniline, and the conductivity σ is pH = 0.77 − 0.64 log(σ [S cm⁻¹]). The wettability, i.e. water contact angles, can similarly be set by partial protonation to between 78° for polyaniline base and 44° for polyaniline reprotonated in 1 mol L⁻¹ phosphoric acid. In solutions of picric acid, the transition from the non‐conducting to the conducting state occurs over a narrow range of acid concentrations, and the tuning of conductivity is consequently difficult. Phosphoric acid is well suited for the control of conductivity of polyaniline because of the moderate dependence of the conductivity on the acid concentration or pH. Copyright © 2007 Society of Chemical Industry