Sequencial Routing Optimization for Circuit Switched Networks

Nonhierarchical alternate routing is the simplest extension to the hierarchical routing currently used in telephone networks. In order to evaluate the merits of such a technique, it is necessary to be able to optimize some performance measure over the routing variables. In a first step, a short discussion is presented of the evaluation algorithms used for computing the end-to-end blocking probabilities in networks operating under nonhierarchicai alternate routings. Then the results of a statistical sampling of the routing space for a small network are presented, to illustrate important characteristics of the routing problem. Next, two heuristic optimization techniques are discussed, one based on classical steepest descent and the other inspired from classical routing optimization of traffic flows in transportation and communication networks. Acceleration techniques are discussed in both cases, and the convergences rates of the alorgithms are presented for a number of networks. A brief discussion is finally given of the usefulness of nonhierarchical alternate routing in reducing the blocking probability in already existing networks, and in decreasing the number of trunks required to maintain a prespecified grade of service, both in real and artificially generated networks.     

Effects of low-dose alcohol exposure on simulated merchant ship piloting by maritime cadets

The US Department of Transportation (DOT) regulates on-the-job alcohol use by operators of certain categories of commercial transport. For aircraft, trains, and commercial vessels, operators are subject to sanctions for having > or = 0.04 g% blood alcohol concentration (BAC). This study examines the effects of alcohol (between 0.04 and 0.05 g% BAC) on simulated merchant ship handling. A two-group randomized factorial design was used to compare beverage alcohol to placebo while controlling for baseline performance on a previous day. The study was conducted in the Maritime Simulation Center at Maine Maritime Academy, Castine, ME. Participants were 38 volunteer deck officer cadets in their junior or senior year, at least 21 years of age, with previous experience on a bridge simulator. Following a baseline trial on Day 1, on Day 2 participants were randomized to receive alcohol (0.6 g/kg for males and 0.5 g/kg for females) or placebo. After allowing time for absorption, participants completed a bridge simulator task. For baseline and performance trials, participants were randomized to one of four bridge simulator scenarios, each representing passage of a fully loaded container vessel through a channel with commercial traffic. The aggregate scenario score given by blinded maritime educators measured performance. A main effect for alcohol was found indicating that performance was significantly impaired by this low dose of alcohol relative to performance in the placebo condition. These findings are consistent with current federal regulations that limit low-dose alcohol exposure for the operators of commercial transport vehicles. Further research is required to determine effects at lower BACs.     

Nickel adsorption by magnetic alginate microcapsules containing an extractant

The adsorption of heavy metals on biomaterials was investigated by studying the potential of alginate microcapsules containing an extractant (Cyanex 272) and magnetic nanoparticles (gamma-Fe2O3) for the adsorption of nickel (II) from aqueous solutions. A two-stage kinetics behaviour was observed with 70% of the maximum sorption capacity achieved within 8 h. An increase in nickel removal with increase in pH occurred, the maximum uptake capacity being around 0.42 mmol g-1 at pH 8. The adsorption isotherm (pH about 5.3) was obtained in a wide range of initial nickel concentrations; the experimental data were fitted by a Langmuir model and the qmax value was estimated to be 0.52 mmol g-1. Moreover, including magnetic particles in the microcapsules allowed easy isolation of the beads from the aqueous solutions after the sorption process. Magnetic microcapsules are then suitable for the development of efficient biosorbents for removal and recovery of heavy metals from wastewater using magnetic separation.     

Characterization of Heterogeneous Soils Using Surface Waves: Homogenization and Numerical Modeling

Seismic surface waves are well-adapted to study the elastic parameters, and hence the mechanical properties, of soils. The aim herein is to evaluate whether Rayleigh waves in heterogeneous soils may be used to estimate average elastic parameters and to determine how these parameters are influenced by heterogeneities. The heterogeneous medium, underlain by a homogeneous half-space, is considered as a homogeneous matrix with one or several types of randomly distributed inclusions (with a normal distribution) in the matrix. Seismic waves generated by surface loads and propagating in this medium were calculated using the finite element method (FEM) and then compared with single- and multiple-scattering homogenization methods. For the FEM calculation, special care was taken to reduce numerical dispersion through the use of elements smaller than 1/20 of the dominant wavelength. The group and phase velocity dispersion curves were measured and inverted in order to obtain the effective shear wave velocity of the heterogeneous medium. The results show a clear dependence of the wave velocity with respect to the nature, concentration, and size of the inclusions. The dependence with respect to the nature and concentration of inclusions coincides with that obtained from a multiple-scattering homogenization method up to an inclusion concentration of approximately 50%.     

Frontal Electroencephalogram Alpha Asymmetry During Sleep: Stability and Its Relation to Affective Style.

Electroencephalogram (EEG) alpha (8-12 Hz) asymmetries were collected from the mid-frontal and central regions during presleep wakefulness and Stage 1, Stage 2, and rapid eye movement (REM) sleep in 11 healthy right-handed participants who were free of psychiatric, neurological, and sleep problems. The authors found significant correlations between presleep wakefulness and different stages of sleep in the frontal, but not central, EEG alpha asymmetry measure. The strongest correlation was between presleep waking and REM sleep, replicating and extending relation earlier work to a normal population. The high degree of association between presleep waking and REM sleep may be a result of high cortical activation common to these states and may reflect a predisposition to different styles of emotional reactivity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Current and future radionuclide speciation studies in biological media

Radionuclides may be released into the environment accidentally or incidentally, which could raise health risks when ingested or inhaled by humans. In order to study the behaviour of radionuclides in the human organism (metabolism, retention, excretion), knowledge of radionuclide speciation is indispensable: speciation governs the transfer, bioavailability and toxicity of elements and is also of considerable interest for decorporation. In this context, the Commissariat à l'Energie Atomique has created a working group on speciation to share data both on thermodynamic constants and on speciation analysis methods of interest to chemists, environmentalists and biologists. The initial focus was on the 31 radionuclides described in different International Commission on Radiological Protection models (HRTM, HAT) and the National Council on Radiation Protection model (wound). Particular attention was devoted to selecting the inorganic and organic ligands, most representative of biological media. The base applied to speciation in solution and at interfaces and solubility (BASSIST) thermodynamic database was developed for this purpose. The aim of this paper is to present the state of the art on radionuclide speciation tools within biological media and to emphasise some missing data in order to orient future research.     

Self‐Propagating Domino‐like Reactions in Oxidized Graphite

Graphite oxide (GO) has received extensive interest as a precursor for the bulk production of graphene‐based materials. Here, the highly energetic nature of GO, noted from the self‐propagating thermal deoxygenating reaction observed in solid state, is explored. Although the resulting graphene product is quite stable against combustion even in a natural gas flame, its thermal stability is significantly reduced when contaminated with potassium salt by‐products left from GO synthesis. In particular, the contaminated GO becomes highly flammable. A gentle touch with a hot soldering iron can trigger violent, catastrophic, total combustion of such GO films, which poses a serious fire hazard. This highlights the need for efficient sample purification methods. Typically, purification of GO is hindered by its tendency to gelate as the pH value increases during rinsing. A two‐step, acid–acetone washing procedure is found to be effective for suppressing gelation and thus facilitating purification. Salt‐induced flammability is alarming for the fire safety of large‐scale manufacturing, processing, and storage of GO materials. However, the energy released from the deoxygenation of GO can also be harnessed to drive new reactions for creating graphene‐based hybrid materials. Through such domino‐like reactions, graphene sheets decorated with metal and metal oxide particles are synthesized using GO as the in situ power source. Enhanced electrochemical capacitance is observed for graphene sheets loaded with RuO₂ nanoparticles.