Localization of Distributed Wireless Sensor Networks using Two Sage SDP Optimization

A wireless sensor network (WSN) may comprise a large distributed set of low cost, low power sensing nodes. In many applications, the location of sensors is a necessity to evaluate the sensed data and it is not energy and cost efficient to equip all sensors with global positioning systems such as GPS. In this paper, we focus on the localization of sensors in a WSN by solving an optimization problem. In WSN localization, some sensors (called anchors) are aware of their location. Then, the distance measurements between sensors and anchors locations are used to localize the whole sensors in the network. WSN localization is a non-convex optimization problem, however, relaxation techniques such as semi-definite programming (SDP) are used to relax the optimization. To solve the optimization problem, all constraints should be considered simultaneously and the solution complexity order is O(n2) where n is the number of sensors. The complexity of SDP prevents solving large size problems. Therefore, it would be beneficial to reduce the problem size in large and distributed WSNs. In this paper, we propose a two stage optimization to reduce the solution time, while provide better accuracy compared with original SDP method. We first select some sensors that have the maximum connection with anchors and perform the SDP localization. Then, we select some of these sensors as virtual anchors. By adding the virtual anchors, we add more reference points and decrease the number of constraints. We propose an algorithm to select and add virtual anchors so that the total solution complexity and time decrease considerably, while improving the localization accuracy

A Methodology to Determine the Effective Plastic Zone Size Around Blunt V-Notches under Mixed Mode I/II Loading and Plane-Stress Conditions

ABSTRACT:The determination of the ductile failure behavior in engineering components weakened by cracks and notches is greatly dependent on the estimation of the plastic zone size (PZS) and, particularly, the effective plastic zone size (EPZS). Usually, time-consuming complex elastic-plastic analyses are required for the determination of the EPZS. Such demanding procedures can be avoided by employing analytical methods and by taking advantage of linear elastic analyses. In this sense, this work proposed a methodology for determining the PZS around the tip of blunt V-notches subjected to mixed mode I/II loading and plane-stress conditions. With this aim, firstly, existing approximate mathematical expressions for the elastic stress field near round-tip V-notches reported in the literature are presented. Next, Irwin's approach (fundamentally proposed for sharp cracks) and a yield criterion (von Mises or Tresca) were applied and are presented. With the aim of verifying the proposed methodology, elastic-plastic finite element analyses were performed on virtual AISI 304 steel V-notched specimens. It was shown that the analytical formulations presented cannot estimate the complete shape of the plastic zone. However, the EPZS, which is crucial for predicting the type of ductile failure in notched members, can be successfully estimated

Extension of the Equivalent Material Concept to Compressive Loading: Combination with LEFM Criteria for Fracture Prediction of Keyhole Notched Polymeric Samples

ABSTRACT: This work analyzes, both theoretically and experimentally, the fracture process of square specimens weakened by keyhole notches and subjected to compressive stresses. Two materials are covered: general-purpose polystyrene (GPPS) and poly(methyl methacrylate) (PMMA). Firstly, the load-carrying capacity (LCC) of the specimens is determined experimentally. Then, by using the equivalent material concept (EMC) for compressive conditions coupled with the maximum tangential stress (MTS) and the mean stress (MS) criteria, the LCC of the notched specimens is predicted. The results show that by using the approach proposed in the present investigation, not only can the critical loads in the keyhole notched polymeric specimens be precisely predicted, but also the corresponding compressive critical stress of the two mentioned polymers can be successfully estimated

Sevelamer, a phosphate-binding resin with beneficial effect in diabetic kidney disease; a modern paradigm shift

The proportion of individuals diagnosed with diabetes mellitus is increasing throughout the world, which sequentially drives upward the global frequency of diabetic kidney disease (1, 2). Diabetes is a costly and deadly disease. Patients with diabetic kidney disease are at an increased risk for cardiovascular disease, premature death, and other severe diseases that ensue in increased health-care utilization and frequent hospitalizations (1, 2). In fact, type II diabetes mellitus is an ongoing medical dilemma that clinicians deal with on a daily basis

In situ probing of electromechanical properties of an individual ZnO nanobelt

We report here, an investigation on electrical and structural-microstructural properties of an individual ZnO nanobelt via in situ transmission electron microscopy using an atomic force microscopy (AFM) system. The I-V characteristics of the ZnO nanobelt, just in contact with the AFM tip indicates the insulating behavior, however, it behaves like a semiconductor under applied stress. Analysis of the high resolution lattice images and the corresponding electron diffraction patterns shows that each ZnO nanobelt is a single crystalline, having wurtzite hexagonal structure (a=0.324 nm, c=0.520 66 nm) with a general growth direction of (1010)

Real-time fracture detection of individual boron nitride nanotubes in severe cyclic deformation processes

Real-time deformation of individual multiwalled boron nitride nanotubes (BNNTs) was investigated using an atomic force microscopy (AFM) stage installed inside the chamber of a transmission electron microscopy (TEM) system. These in situ AFM-TEM experiments were conducted in following two deformation regimes: a small-angle (∼65°) and a large-angle (∼120°) cyclic bending process. BNNTs survived from the low-angle test and their modulus was determined as ∼0.5 TPa. Fracture failure of individual BNNTs was discovered in the large-angle cyclic bending. The brittle failure mechanism was initiated from the outermost walls and propagated toward the tubular axis with discrete drops of applied force

Aggressive jaw brown tumor in a 28-year-old man with long-lasted chronic kidney disease

Brown tumors are bony lesions triggered by rapid osteoclastic activity, which rarely involved jaws (1-3). In fact brown tumors or osteoclastomas are erosive bony lesions appearing as a complication of hyperparathyroidism. Renal osteodystrophy is the result of secondary hyperparathyroidism and is associated with various pathogenetic mechanisms, such as disorder of calcium-phosphate metabolism, increased parathyroid activity that lead to extreme concentrations of parathormone and impaired metabolism of vitamin D (1-7). We