Characterization of the loss allocation techniques for radial systems with distributed generation

In the restructured electricity industry, meaningful loss allocation methods are required in order to send correct signals to the market taking into account the location and characteristics of loads and generations, including the local sources forming the distributed generation (DG). This paper addresses the issues related to loss allocation in radial distribution systems with DG, with a three-fold focus. First, the key differences in the formulation of the loss allocation problem for radial distribution systems with respect to transmission systems are discussed, specifying the modeling and computational issues concerning the treatment of the slack node in radial distribution systems. Then, the characteristics of derivative-based and circuit-based loss allocation techniques are presented and compared, illustrating the arrangements used for adapting the various techniques to be applied to radial distribution systems with DG. Finally, the effects of introducing voltage-controllable local generation on the calculation of the loss allocation coefficients are discussed, proposing the adoption of a “reduced” representation of the system capable of taking into proper account the characteristics of the nodes containing voltage-controllable DG units. Numerical results are provided to show the time evolution of the loss allocation coefficients for distribution systems with variable load and local generation patterns.     

Ettringite and calcium sulfoaluminate cement: investigation of water content by near-infrared spectroscopy

Calcium sulfoaluminate (CSA) cement is a sulfate-based binder whose high-performance hydraulic behavior depends on the rapid formation of ettringite, when grinded clinker is hydrated in presence of gypsum. Ettringite is a calcium aluminum sulfate mineral characterized by high water content, estimated as 32 water molecules per formula unit. Three examples of utilization of near-infrared (NIR) spectroscopy are here shown. First of all, information on water distribution in pure ettringite was deduced and compared with infrared analyses. Then its thermal behavior has been followed up to 400 °C, allowing to improve the knowledge about water loss and thermal decomposition of this hydrated phase. Finally, the obtained results have been employed in order to follow hydration of CSA cement sample, demonstrating thus that NIR spectroscopy, being highly sensitive to water amount and distribution, can be an extremely useful tool for hydration studies.     

The PTB primary standard for electrical AC power

The present PTB primary standard allows power measurements with a measurement uncertainty of about 2.5 μW / VA (k = 2). It operates at voltages up to 240 V and currents up to 10 A in the frequency range from 16 Hz up to some kHz. This paper gives a short overview of the working principle of the standard and recent improvements.     

A TEM and SEM-cathodoluminescence study of oval defects in graded InGaAs/GaAs buffer layers

The nature of oval defects in compositionally graded InGaAs/GaAs buffer layers has been investigated by means of Transmission electron microscopy (TEM) and Cathodoluminescence (CL). CL spectra show that emissions from within the defects have energies lower than that from the defect-free regions, thus demonstrating that the defects are richer in In than the surrounding matrix. No In particles have been detected within the defect core. TEM investigations reveal that the defects form in the topmost strained regions close to the surface and originate from stacking faults.     

ORION — Ontology-based queRy routIng in Overlay Networks

Current search engines are rapidly changing to embrace more powerful mechanisms that are capable of reasoning on semantic attributes of contents in a distributed repository. Formalisms have been proposed to represent the semantic attributes. Yet, traditional approaches for content sharing in peer-to-peer systems cannot be adapted to use semantic information. Some novel proposals in the literature consider semantic aspects in P2P systems. However, they either make strong assumptions on the semantic model, or have high communication and computation overhead.     

A metal hydride–polymer composite for hydrogen storage applications

To address the issue of the breakdown into fine powders that occurs in the practical use of metal hydrides, the possibility of using a polymeric material as a matrix that contains the active metal particles was experimentally assessed. A ball milling approach in the tumbling mode was used to develop a metal hydride–polymer composite with a high metal to polymer weight ratio. The alloy powder was blended with the polymer and a coating of the metal particles was obtained. The composite was consolidated by hot pressing and the pellets were characterized in terms of their hydriding–dehydriding properties. The materials did not show significant losses in either loading capacity or kinetic properties. The polymeric matrix resulted as being stable under hydrogen cycling. Further, from SEM observation it was confirmed that the metal powders remained embedded in the polymeric matrix even after a number of cycles and that the overall dimensional integrity was retained.     

e-Science, caGrid, and Translational Biomedical Research

Translational research projects target a wide variety of diseases, test many different kinds of biomedical hypotheses, and employ a large assortment of experimental methodologies. Diverse data, complex execution environments, and demanding security and reliability requirements make the implementation of these projects extremely challenging and require novel e-Science technologies.     

A combination of Monte Carlo simulation and cellular automata for computing the availability of complex network systems

This paper combines Monte Carlo simulation and cellular automata for computing the availability of a complex network system and the importance measures of its elements.     

Efficient unbalanced merge-sort

Sorting algorithms based on successive merging of ordered subsequences are widely used, due to their efficiency and to their intrinsically parallelizable structure. Among them, the merge-sort algorithm emerges indisputably as the most prominent method. In this paper we present a variant of merge-sort that proceeds through arbitrary merges between pairs of quasi-ordered subsequences, no matter which their size may be. We provide a detailed analysis, showing that a set of n elements can be sorted by performing at most n⌊logn⌋ key comparisons. Our method has the same optimal asymptotic time and space complexity as compared to previous known unbalanced merge-sort algorithms, but experimental results show that it behaves significantly better in practice.     

Evaluation of global biomass devolatilization kinetics in a drop tube reactor with CFD aided experiments

A procedure coupling experimental characterization and computational fluid dynamics (CFD) is developed for providing valuable global kinetic parameters to large applications of biomass fuels (fast pyrolysis, co-combustion and gasification). This is based on an advanced lab-scale apparatus (drop tube reactor), reproducing high heating rates and low residence times at different nominal temperatures (400-800 °C) for particle size of practical interest. Although the relative simplicity of the operation, a detailed and accurate evaluation of the particle residence time and effective thermal history is needed to elaborate suitable global devolatilization kinetics, which differ significantly from low heating rate kinetics (for instance in thermogravimetric balance) and also from those obtained assuming strong hypotheses (e.g. constant particle temperature in the reactor). The developed procedure gives kinetic parameters which are not the intrinsic devolatilization kinetics but global kinetics at high heating rates. These global kinetic parameters are useful to simulate practical systems (characterised by high heating rate) with comprehensive codes (CFD), since detailed particle kinetics require additional sub-models (e.g. of external and internal heat transfer) which may be time consuming and need many data, often known only with uncertainty. In this work CFD is used as both diagnostic and predictive tool; its potentials and drawbacks in aiding advanced experimentation on biomass/coal pyrolysis are discussed.