An Energy-Efficient Routing Protocol for Event-Driven Dense Wireless Sensor Networks

The routing energy efficiency of a wireless sensor network is a crucial issue for the network lifetime. In this article, we propose MICRO (MInimum Cost Routing with Optimized data fusion), an energy-efficient routing protocol for event-driven dense wireless sensor networks. The proposed routing protocol is an improvement over the formerly proposed LEACH and PEGASIS protocol, which is designed to be implemented mainly with node computations rather than mainly with node communications. Moreover, in the routing computation the proposed scheme exploits a new cost function for energy balancing among sensor nodes, and uses an iterative scheme with optimized data fusions to compute the minimum-cost route for each event-detecting sensor node. Compared to the PEGASIS routing protocol, MICRO substantially improves the energy-efficiency of each route, by optimizing the trade-off between minimization of the total energy consumption of each route and the balancing of the energy state of each sensor node. It is demonstrated that the proposed protocol is able to outperform the LEACH and the PEGASIS protocols with respect to network lifetime by 100–300% and 10–100%, respectively.     

Compliance error compensation technique for parallel robots composed of non-perfect serial chains

The paper presents the compliance errors compensation technique for over-constrained parallel manipulators under external and internal loadings. This technique is based on the non-linear stiffness modeling which is able to take into account the influence of non-perfect geometry of serial chains caused by manufacturing errors. Within the developed technique, the deviation compensation reduces to an adjustment of a target trajectory that is modified in the off-line mode. The advantages and practical significance of the proposed technique are illustrated by an example that deals with groove milling by the Orthoglide manipulator that considers different locations of the workpiece. It is also demonstrated that the impact of the compliance errors and the errors caused by inaccuracy in serial chains cannot be taken into account using the superposition principle.     

Perfluorinated alkyl substances in plasma, liver, brain, and eggs of glaucous gulls (Larus hyperboreus) from the Norwegian arctic

Recent environmental surveys have ascertained the widespread occurrence of perfluorinated alkyl substances (PFAS) in tissues of wildlife from the Arctic. In the present study, we investigated the distribution of a suite of PFAS in plasma, liver, brain, and egg samples from adult glaucous gulls (Larus hyperboreus), an apex scavenger-predator seabird breeding in the Norwegian Arctic. Perfluorooctane sulfonate (PFOS) was the predominant PFAS in all samples and was present at concentrations that are the highest reported thus far in any arctic seabird species and populations. Among the body compartment/ tissue samples analyzed, PFOS was highest in plasma (48.1-349 ng/g wet weight (ww)), followed by liver approximately equal to egg > brain. Perfluorocarboxylic acids (PFCAs) with 8-15 carbon (C) atoms were found, with the highest concentrations determined in plasma (sum PFCA: 41.8-262 ng/g ww), whereas 5C- and 6C-PFCAs were below the limits of detection. Perfluorobutane sulfonate, perfluorooctane sulfonamide, and four saturated (8:2 FTCA and 10:2 FTCA) and unsaturated (8:2 FTUCA and 10:2 FTUCA) fluorotelomer carboxylic acids were not detected in any samples. Perfluorohexane sulfonate was measured at concentrations up to 2.71 ng/g ww. The accumulation profiles of PFCAs were characterized by high proportions of the long and odd-numbered carbon-chain-length compounds, namely perfluoroundecanoic (11C) and perfluorotridecanoic acid (13C), although their individual contribution differed between the matrixes analyzed. Current PFAS concentrations suggest a bioaccumulation potential in Norwegian arctic glaucous gulls that needs to be assessed as part of a broad organohalogen contaminant cocktail with potential for mediating biological processes in this vulnerable top-predator marine species.     

Brominated flame retardants in glaucous gulls from the Norwegian Arctic: more than just an issue of polybrominated diphenyl ethers

Several, unregulated, current-use brominated flame retardants (BFRs), including hexabromobenzene (HBB), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), pentabromoethylbenzene (PBEB), pentabromotoluene (PBT), and hexabromocyclododecane (as total-(alpha)-HBCD), were examined in egg yolk and plasma of male and female glaucous gulls (Larus hyperboreus) from the Norwegian Arctic. Also examined were BDE209 and 38 tri- to nona-BDE congeners and brominated biphenyl (BB) 101. The HBB, BTBPE, PBEB, and PBT had high detection frequencies and variability in male and female plasma and egg yolk samples, and their concentrations ranged from nondetectable (< 0.02-0.27 ng/g wet wt) to 2.64 ng/g wet wt. The detection frequencies and range of concentrations of non-BDE BFRs were generally highest in plasma of males relative to females. Total-(alpha)-HBCD concentrations were highest among the non-PBDE BFRs (up to 6.12 and 63.9 ng/g wet wt in plasma and egg yolk, respectively). Next highest was HBB with concentrations within a range comparable to the minor PBDEs monitored (e.g., BDE28, 116 and 155). Sum (sigma)38PBDE concentrations ranged from 2.49 to 54.5 ng/g wet wt in plasma and 81.2 to 321 ng/g wet wt in egg yolk. The BDE209 was virtually nondetectable, whereas six octa-BDEs (i.e., BDE196, 197, 201, 202, 203, and 205), as well as three nona-BDEs (i.e., BDE206, 207, and 208, and potential BDE209 debromination products) were found sporadically in plasma and egg yolk. The results from this study suggestthat in addition to PBDEs, several current-use, non-BDE BFRs undergo long-range atmospheric transport and bioaccumulate at low levels in and are maternally transferred (to eggs) in glaucous gulls from the Norwegian Arctic.     

The influence of physical and chemical factors on the transport of E. coli through biological filters for wastewater purification

Transport studies of Escherichia coli were performed in laboratory columns over a period of 15 months. The effects of the filter media properties, effective grain size, specific surface area, pH and cation exchange capacity were examined for loading rates of 25 mm and 50 mm/day applied as 8 doses per day. Distilled water and two solutions of ionic strength 0.00725 and 0.097 M were applied to the columns. Physical factors were found to be the most important for the removal of E. coli. Reduced grain size, hydraulic loading rate and increased specific surface area of the grains significantly reduced transport of E. coli. Chemical factors such as pH, cation exchange capacity and wastewater ionic strength showed less significant effects. The results indicate that the chemical factors in biological wastewater filters have a minor influence on the removal of E. coli after a stabilizing period of three months. Minimum hydraulic retention time (time required for 10% breakthrough of a conservative tracer) was found to be the most relevant parameter for predicting bacterial removal in unsaturated filter systems. Correlation between observed data and a first order removal model, based on minimum retention time, was 0.70.     

Built-in self test of S2I switched current circuits

This article presents a new concept for built-in self test of switched current circuits based on S²I memory cells. From the spectrum of possible transistor defects reported in CMOS processes [1] [2], five different fault-situations were modelled and the ability to detect the various failures was studied. This was accomplished by simulating a simple switched-current integrator in which all the different failures were introduced sequentially in all transistors. The fault coverage was derived and the result shows that a powerful system for detection of transistor faults in an analogue sampled-data system can be readily realised with a minimum of additional overhead circuitry.     

Reliability investigation and characterization of failure modes in Schottky diodes

Schottky diodes may be realized by various techniques, depending on application and processing technology. M/A-COM has recently developed an enhancement/depletion (E/D) pHEMT process, used primarily for control circuits around its mature RF circuitry. We report here a reliability study of two diodes (configured using E-FETs), subjected to both high temperature and forward bias accelerated stress. Different failure modes observed during accelerated life tests of the two diode configurations are discussed, and the causes for aging are analyzed. Results of the stress test are backed by equivalent circuit modeling using ADS™. The differences in the effect of these failure modes on circuit performance are discussed.     

A transmission electron microscope and electron diffraction study of carbon nanodisks

The pyrolytic Kvaerner carbon-black and hydrogen process yields industrial amounts of carbon nanodisks and nanocones. We here report on the first detailed transmission electron microscope and electron diffraction study of such carbon nanodisks. The carbon nanodisk rim thickness ranges from 5–6 nm to 60–70 nm, but most disks are 10–30 nm thick. In agreement with earlier reported results, we find that the disk diameters fall within the range from 500 to 4000 nm. Most nanodisks display six identical pairs of facets. The two associated interfacial angles are θ₁ = (22 ± 1)° and θ₂ = 60.0°−θ₁. The nanodisk fracture surfaces reveal that the nanodisks are multi-layered structures. When the incident electron beam is perpendicular to the plane of the nanodisk we find that the diffraction patterns consist of concentric and continuous rings, on top of which there are discrete sets of diffraction spots. These spots display six-fold rotational symmetry and are consistent with the diffraction patterns of graphite layers.     

Carbon nanocones: wall structure and morphology

Large-scale production of conical carbon nanostructures is possible through pyrolysis of hydrocarbons in a plasma torch process. The resulting carbon cones occur in five distinctly different forms, and disc-shaped particles are produced as well. The structure and properties of these carbon cones and discs have been relatively little explored until now. Here we characterize the structure of these particles using transmission electron microscopy, synchrotron x-ray and electron diffraction. The carbon nanocones are found to exhibit several interesting structural features; instead of having a uniform cross-section, the walls consist of a relatively thin inner graphite-like layer with a non-crystalline envelope, where the amount of the latter can be modified significantly by annealing. The cones appear with a well-defined faceting along the cone edge, demonstrating strict long-range atomic ordering; they also present occasional examples of symmetry breaking, such as two apexes appearing in the same carbon nanocone.