An improved voltage control on large-scale power system

To achieve a better voltage-VAr control in the electric power transmission system, different facilities are used. Generators are equipped with automatic voltage regulators to cope with sudden and random voltage changes caused by natural load fluctuations or failures. Other devices like capacitors, inductors, transformers with on load tap changers are installed on the network. Faced with the evolution of the network and operating conditions, electricity utilities are more and more interested in overall and coherent control systems, automatic or not. These systems are expected to co-ordinate the actions of local facilities for a better voltage control (more stable and faster reaction) inside different areas of the network in case of greater voltage and VAr variations. They afford a better use of existing reactive resources. Also, installation of new devices can be avoided allowing economy of investment. With this in mind, EDF has designed a system called Co-ordinated Secondary Voltage Control (CSVC). It is an automatic closed loop system with a dynamic of a few minutes. It takes into account the network conditions (topology, loads), the voltage limits and the generator operating constraints. This paper presents improvements which allow the CSVC to control the voltage profile and different kinds of reactive means on a large-scale power system, Furthermore, this paper presents a solution to spread out investment costs over several years, considering a deployment gradually extended     

Growth and electrical properties of pure and Ni-doped Co3O4 single crystals

Single crystals of pure and Ni-doped Co₃O₄ spinel-type phases have been grown by C.V.T. Electrical conductivity and thermopower measurements have been performed between 25 and 950 K. Ni-doping gives rise to a significant increase of electrical conductivity at room temperature by three orders of magnitude. The obtained results suggest that the Ni atoms are located in the octahedral sites of the spinel lattice with both oxidation states 2+ and 3+, as illustrated by the formula : Co²⁺_1?yCo³⁺_y[Co³⁺_2?xNi²⁺_yNi³⁺_x?y]O₄.     

An A Contrario Decision Method for Shape Element Recognition

Shape recognition is the field of computer vision which addresses the problem of finding out whether a query shape lies or not in a shape database, up to a certain invariance. Most shape recognition methods simply sort shapes from the database along some (dis-)similarity measure to the query shape. Their main weakness is the decision stage, which should aim at giving a clear-cut answer to the question: “do these two shapes look alike?” In this article, the proposed solution consists in bounding the number of false correspondences of the query shape among the database shapes, ensuring that the obtained matches are not likely to occur “by chance”. As an application, one can decide with a parameterless method whether any two digital images share some shapes or not.     

Fully-planar AlGaAs/GaAs HBT's achieved by selective CBE regrowth

This paper describes a novel fully planar AlGaAs/GaAs heterojunction bipolar transistor (HBT) technology using selective chemical beam epitaxy (CBE). Planarization is achieved by a selective regrowth of the base and collector contact layers. This process allows the simultaneous metallization of the emitter, base and collector on top of the device. For the devices with an emitter-base junction area of 2×6 μm² and a base-collector junction area of 14×6 μm², a current gain cut off frequency of 50 GHz and a maximum oscillation frequency of 30 GHz are achieved. The common emitter current gain h_FE is 25 for a collector current density J_c of 2×10⁴ A/cm²     

On the Mechanisms Governing Aluminum-Mediated Solid-Phase Epitaxy of Silicon

Mechanisms governing the aluminum-mediated solid-phase epitaxy of Si on patterned crystalline Si substrates have been identified by studying the deposited material as a function of growth conditions when varying parameters such as temperature, growth time, and layer-stack properties. Early growth stages can be discerned as first formation of “free” Si at the Al/α-Si interface, then diffusion of Si along the Al grain boundaries, nucleation at the Si substrate surface, nuclei rearrangement, and finally crystal growth. The acquired understanding is applied to control the selectivity and completeness of single-crystal growth in various sizes of contact windows to the Si substrate.     

Indexing of satellite images with different resolutions by wavelet features

Space agencies are rapidly building up massive image databases. A particularity of these databases is that they are made of images with different, but known, resolutions. In this paper, we introduce a new scheme allowing us to compare and index images with different resolutions. This scheme relies on a simplified acquisition model of satellite images and uses continuous wavelet decompositions. We establish a correspondence between scales which permits us to compare wavelet decompositions of images having different resolutions. We validate the approach through several matching and classification experiments, and we show that taking the acquisition process into account yields better results than just using scaling properties of wavelet features.     

Confounding Roles of ER Stress and the Unfolded Protein Response in Skeletal Muscle Atrophy

Skeletal muscle is an essential organ, responsible for many physiological functions such as breathing, locomotion, postural maintenance, thermoregulation, and metabolism. Interestingly, skeletal muscle is a highly plastic tissue, capable of adapting to anabolic and catabolic stimuli. Skeletal muscle contains a specialized smooth endoplasmic reticulum (ER), known as the sarcoplasmic reticulum, composed of an extensive network of tubules. In addition to the role of folding and trafficking proteins within the cell, this specialized organelle is responsible for the regulated release of calcium ions (Ca²⁺) into the cytoplasm to trigger a muscle contraction. Under various stimuli, such as exercise, hypoxia, imbalances in calcium levels, ER homeostasis is disturbed and the amount of misfolded and/or unfolded proteins accumulates in the ER. This accumulation of misfolded/unfolded protein causes ER stress and leads to the activation of the unfolded protein response (UPR). Interestingly, the role of the UPR in skeletal muscle has only just begun to be elucidated. Accumulating evidence suggests that ER stress and UPR markers are drastically induced in various catabolic stimuli including cachexia, denervation, nutrient deprivation, aging, and disease. Evidence indicates some of these molecules appear to be aiding the skeletal muscle in regaining homeostasis whereas others demonstrate the ability to drive the atrophy. Continued investigations into the individual molecules of this complex pathway are necessary to fully understand the mechanisms.