Efficient visualization of large routing topologies

As the Internet grows in size and complexity, network managers face a significant challenge in trying to understand the behaviour of routing protocols in large networks. In this paper, we present a tool called VLNT (visualizing large network topologies), which helps network managers to analyse complex routing topologies. A key contribution of our system is a novel hybrid layout algorithm, which significantly reduces the computation time required to layout large network topologies in comparison to conventional layout approaches. In addition our algorithm includes a novel termination criterion that avoids unnecessary iterations when optimizing the network layout. We demonstrate how the visualization features of VLNT can be used to analyse and improve BGP routing topologies, and provide examples using real‐life routing data. Copyright © 2004 John Wiley & Sons, Ltd.     

Flexibility valuation in the Brazilian power system: A real options approach

This paper presents a valuation study of operational flexibility in the complex Brazilian Power System. Thermopower plants represent operational flexibility for the national system operator provided they can be dispatched in dry periods to supply part of the load when reservoir waters are too low. Deficit costs can be avoided as a result.

We have adopted a real options approach to calculate the fair value of a financial subsidy to be paid to thermal generators for their availability to the system. A financial subsidy is mandatory for their economic feasibility and, therefore, for increased thermopower capacity in the Brazilian Power System. This is why this policy is currently being studied by Brazil's federal government.

In order to illustrate our modeling we have run the model for the southeast subsystem. We found a flexibility value of US$4.52 billion, which represents US$497/MW per year. This means that a 100 MW thermopower plant should receive US$49,700 for each year of its economic lifetime as a fair premium incentive to investments.     

Evaluation,modification and comparison of two rapid assays for cyanogens in cassava

Two rapid semi-quantitative assays for total cyanogens in cassava were evaluated. These were the well-known rapid picrate paper test, and a recently proposed rapid paper test involving the reagent tetra base (TB, 4,4′- methylenebis-(N, N-dimethylaniline)). A precise colorimetric assay was used as a control in the evaluative work. After primary evaluation, both assay methods underwent some modification regarding the interpretation of sample scores. As a result, the reliability of the picrate assay was greatly improved. The TB assay was modified in the interests of safety. Evaluation of this assay over a range of temperatures between 20 and 35°C showed no significant temperature effects upon performance when the new scoring interpretation system was used. The level of endogenous linamarase activity in the sample was found to be an influential factor in rapid assay performance. In a series of comparative trials in three distinct ecosystems, the newly modified picrate assay produced correct results in 68% of cases. This compared with 66% of results correct in the TB assay. It was observed that the TB assay performed more reliably with low cyanogen samples, whilst the picrate assay was more reliable with intermediate cyanogen samples.     

Advances in internet congestion control

In this survey, we first review the concept of congestion control with a focus on the Transmission Control Protocol⁄Internet Protocol (TCP⁄IP). We describe many recently proposed algorithms to combat congestion and improve performance, particularly active queue management (AQM) algorithms such as random early detection (RED) and its variants. We then survey control-theoretic analysis and design of TCP congestion control with an AQM scheme. In addition, we discuss three problems associated with AQM proposals: parameter setting, the insensitivity to the input traffic load variation, and the mismatch between macroscopic and microscopic behavior of queue length dynamics. As alternatives to AQM algorithms, we also survey architectural approaches such as modification of source or network algorithms, and economic approaches including pricing or optimization of allocated resources. Finally, we list many open issues that persist in the design, operation, and control of the Internet.     

Combined Optical and MR Bioimaging Using Rare Earth Ion Doped NaYF4 Nanocrystals

Here, novel nanoprobes for combined optical and magnetic resonance (MR) bioimaging are reported. Fluoride (NaYF₄) nanocrystals (20–30 nm size) co‐doped with the rare earth ions Gd³⁺ and Er³⁺/Yb³⁺/Eu³⁺ are synthesized and dispersed in water. An efficient up‐ and downconverted photoluminescence from the rare‐earth ions (Er³⁺ and Yb³⁺ or Eu³⁺) doped into fluoride nanomatrix allows optical imaging modality for the nanoprobes. Upconversion nanophosphors (UCNPs) show nearly quadratic dependence of the photoluminescence intensity on the excitation light power, confirming a two‐photon induced process and allowing two‐photon imaging with UCNPs with low power continuous wave laser diodes due to the sequential nature of the two‐photon process. Furthermore, both UCNPs and downconversion nanophosphors (DCNPs) are modified with biorecognition biomolecules such as anti‐claudin‐4 and anti‐mesothelin, and show in vitro targeted delivery to cancer cells using confocal microscopy. The possibility of using nanoprobes for optical imaging in vivo is also demonstrated. It is also shown that Gd³⁺ co‐doped within the nanophosphors imparts strong T1 (Spin‐lattice relaxation time) and T2 (spin‐spin relaxation time) for high contrast MR imaging. Thus, nanoprobes based on fluoride nanophosphors doped with rare earth ions are shown to provide the dual modality of optical and magnetic resonance imaging.     

High‐Mobility ZnO Thin Film Transistors Based on Solution‐processed Hafnium Oxide Gate Dielectrics

The properties of metal oxides with high dielectric constant (k) are being extensively studied for use as gate dielectric alternatives to silicon dioxide (SiO₂). Despite their attractive properties, these high‐k dielectrics are usually manufactured using costly vacuum‐based techniques. In that respect, recent research has been focused on the development of alternative deposition methods based on solution‐processable metal oxides. Here, the application of the spray pyrolysis (SP) technique for processing high‐quality hafnium oxide (HfO₂) gate dielectrics and their implementation in thin film transistors employing spray‐coated zinc oxide (ZnO) semiconducting channels are reported. The films are studied by means of admittance spectroscopy, atomic force microscopy, X‐ray diffraction, UV–Visible absorption spectroscopy, FTIR, spectroscopic ellipsometry, and field‐effect measurements. Analyses reveal polycrystalline HfO₂ layers of monoclinic structure that exhibit wide band gap (≈5.7 eV), low roughness (≈0.8 nm), high dielectric constant (k ≈ 18.8), and high breakdown voltage (≈2.7 MV/cm). Thin film transistors based on HfO₂/ZnO stacks exhibit excellent electron transport characteristics with low operating voltages (≈6 V), high on/off current modulation ratio (～10⁷) and electron mobility in excess of 40 cm² V^?1 s^?1.     

Investigation for long wavelength fir laser lines for EPR studies: New lines from CH2=CF2

The results described in this work are part of a systematic search for long wavelength laser lines to be used in high magnetic field EPR applications and in plasma diagnostic. Four new far-infrared laser lines of CH₂ = CF₂ (1,1 difluoroethylene), optically pumped by a waveguide CO₂ laser, have been discovered and characterized in wavelength, polarization relative to the pumping radiation and offset relative to the CO₂ center frequency. New measurements of polarization and offset of 5 already known laser lines are also reported. A table of all of the known CO₂ pumped FIR laser lines from this molecule is given.     

'Polymorph Method' Determination of Monoclinic Zirconia in Partially Stabilized Zirconia Ceramics

The polymorph method, which provides phase analysis from a small number of integrated intensities in a powder diffraction scan, is adapted for the determination of monoclinic zirconia in a mixture with cubic, tetragonal. and orthorhombic zirconias and the γ-phase (Mg₂Zr₅O₁₂). Such a mixture is representative of Mg-PSZ after subeutectoid aging. The quantitative determination of the monoclinic depends in principle on a knowledge of the relative amounts of the other phases present in the mixture. It is demonstrated, however, that without this knowledge, even in complex mixtures, the traditional polymorph method analysis gives an acceptable estimate of the monoclinic fraction in the sample.     

Doping efficiency and energy-level scheme in C60F48-doped zinc–tetraphenylporphyrin films

High resolution synchrotron-based core level spectroscopy was used to examine the energy level alignment at the interface of zinc–tetraphenylporphyrin films doped by the surface acceptor C₆₀F₄₈. Two distinct fluorofullerene charge states were identified, corresponding to ionized and neutral molecules, and their relative concentration as a function of coverage was used to evaluate the probability of occupation of the acceptor lowest unoccupied molecular orbital (LUMO). From an initial acceptor energy of ?0.25 eV, the C₆₀F₄₈ LUMO shifts upwards with coverage due to a doping-induced interfacial dipole potential, and stabilization of the LUMO at an energy 0.45 eV above the Fermi energy was obtained. While the energy difference upon saturation is consistent with the results obtained for other donor–acceptor systems that have been interpreted as Fermi level pinning, the present work shows that the energy offset is a direct consequence of the interplay between Fermi–Dirac statistics in combination with the interfacial dipole potential.     

Automated design of robust discriminant analysis classifier for foot pressure lesions using kinematic data

In the recent years, the use of motion tracking systems for acquisition of functional biomechanical gait data, has received increasing interest due to the richness and accuracy of the measured kinematic information. However, costs frequently restrict the number of subjects employed, and this makes the dimensionality of the collected data far higher than the available samples. This paper applies discriminant analysis algorithms to the classification of patients with different types of foot lesions, in order to establish an association between foot motion and lesion formation. With primary attention to small sample size situations, we compare different types of Bayesian classifiers and evaluate their performance with various dimensionality reduction techniques for feature extraction, as well as search methods for selection of raw kinematic variables. Finally, we propose a novel integrated method which fine-tunes the classifier parameters and selects the most relevant kinematic variables simultaneously. Performance comparisons are using robust resampling techniques such as Bootstrap 632+ and k-fold cross-validation. Results from experimentations with lesion subjects suffering from pathological plantar hyperkeratosis, show that the proposed method can lead to approximately 96% correct classification rates with less than 10% of the original features.