Influence of the interface structure on the thermo-mechanical properties of Cu–X (X = Cr or B)/carbon fiber composites

This study focuses on the fabrication, for power electronics applications, of adaptive heat sink material using copper alloys/carbon fibers (CF) composites. In order to obtain composite material with good thermal conductivity and a coefficient of thermal expansion close to the ceramic substrate, it is necessary to have a strong matrix/reinforcement bond. Since there is no reaction between copper and carbon, a carbide element (chromium or boron) is added to the copper matrix to create a strong chemical bond. Composite materials (Cu–B/CF and Cu–Cr/CF) have been produced by a powder metallurgy process followed by an annealing treatment in order to create the carbide at the interphase. Chemical (Electron Probe Micro-Analysis, Auger Electron Spectroscopy) and microstructural (Scanning and Transmission Electron Microscopies) techniques were used to study the location of the alloying element and the carbide formation before and after diffusion. Finally, the thermo-mechanical properties have been measured and a promising composite material with a coefficient of thermal expansion 25% lower than a classic copper/carbon heat sink has been obtained.     

Effect of Water Vapor on the Oxidation Mechanisms of a Commercial Stainless Steel for Interconnect Application in High Temperature Water Vapor Electrolysis

High temperature water vapor electrolysis is one of the most promising methods for hydrogen production. The interconnect is a key component in the electrolyse technology. In a previous paper, the high temperature corrosion resistance and the electrical conductivity of a commercial ferritic stainless steel, K41X (AISI 441), were assessed in both anode (95 %O₂–5 %H₂O) and cathode atmospheres (10 %H₂–90 %H₂O). In cathode atmosphere, ageing tests performed up to 1,000 h revealed the formation of a duplex oxide scale: an inner layer consisting of protective chromia and an outer layer comprised of a magnetite-type iron oxide. In this study, we further investigated the oxidation mechanisms of K41X alloy in cathode atmosphere by means of marker experiments using an inert marker (Au) and isotopes. SEM-EDX and SIMS characterizations were combined in order to determine the oxide scale growth processes. The roles played by hydrogen and water vapor are discussed and a diffusion mechanism is postulated.     

An optimum modulation strategy for a novel "notch" commutated 3-/spl Phi/ PWM inverter

The introduction of soft switching features in medium power static converters promises improved semiconductor utilization and higher switching frequencies. In this paper a DC-side commutated zero voltage switching (ZVS) PWM 3-/spl Phi/ VSI topology is discussed. This topology consists of a typical six-switch bridge with the addition of a simple DC bus commutating subcircuit which can provide, on demand, the necessary soft switching zero-volts interval across the inverter DC bus. The objective of this paper is to identify a specific PWM technique which, in combination with the proposed ZVS scheme, can provide optimum overall converter switching performance. Moreover, the combination of the inverter topology and the modulation strategy proposed here yields a soft switching environment at the lowest possible switching frequency. Reduction in switching losses is further enhanced by increasing the effective and reducing the actual switching frequency. Finally, this paper includes a detailed analysis and design procedure for the proposed notch commutated inverter topology. Simulation and experimental results are also presented to verify key predicted results.<>     

Training neural networks on artificially generated data: a novel approach to SAR speckle removal

A neural network-based method for speckle removal in synthetic aperture radar (SAR) images is introduced. The method rests on the idea that a neural network learning machine, trained on artificially generated input–target couples, can be used to efficiently process real SAR data. The explicit plus-point of the method is that it is trained with artificially generated data, reducing the demands put on real input data such as data quality, availability and cost price. The artificial data can be generated in such a way that they fit the particular characteristics of the images to be denoised, yielding case-specific, high-performing despeckling filters. A comparative study with three classical denoising techniques (Enhanced Frost (EF), Enhanced Lee (EL) and Gamma MAP (GM)) and a wavelet filter demonstrated a superior speckle removal performance of the proposed method in terms of quantitative performance measures. Moreover, qualitative evaluation of the despeckled results was in favour of the proposed method, confirming its speckle removal efficiency.     

Melt Crystallization of Ammonium Dinitramide (ADN) Investigated by Means of X-ray Diffraction

Ammonium dinitramide (ADN) is a promising oxidizing agent for solid rocket propellants. In situ XRD investigations of ADN and ADN suspensions have been performed in order to understand and refine the emulsion crystallization process for manufacturing spherical ADN particles (prills). The investigation revealed that the melt crystallization behavior depends on ADN quality, humidity, maximum temperature of temperature cycles, and suspension agents. Further investigations will focus on additives for controlling the mechanisms investigated, e.g., by seeding.     

Theoretical Investigation of the Size Effect on the Oxygen Adsorption Energy of Coinage Metal Nanoparticles

Catalysis Letters - This study evaluates the finite size effect on the oxygen adsorption energy of coinage metal (Cu, Ag and Au) cuboctahedral nanoparticles in the size range of 13 to 1415 atoms...     

Lane keeping based on location technology

Vehicle positioning with an accuracy of 10 cm or less will enable lane-keeping assistance in addition to other safety benefits when an enhanced lane-level digital map is in place. With constantly evolving technology and sensors, a high-precision positioning system that fits into the automotive market can be expected within the next decade. Such a system will incorporate Global Positioning System (GPS) and inertial system (INS) for enhanced positioning performance and availability. In this paper, the technology fields that will have a significant impact on the deployment of a centimeter-level vehicle-positioning system will be discussed. Vision-based lane-recognition (VBLR) systems are relatively mature and have already been introduced to the market for lane-departure warning, etc. However, both systems have some limitations. GPS/INS-based systems may suffer from frequent satellite signal masking or blockage, while vision-based systems do not work well in adverse weather conditions or with poor lane signature. Effectively combining these two technologies can make a robust lane-departure warning system. A precision map was made for the test area near Stuttgart using DaimlerChrysler Research and Technology North America (RTNA)'s map-making approach. A Mercedes S-class equipped with both a vision system and a high-precision GPS/INS was used for the test. The positioning map-matching results and the vision offset are compared and the complementary effectiveness is illustrated.     

Customer-Owned Back-Up Generators for Energy Management by Distribution Utilities

This paper develops a quantification of the most important benefits brought about by the systematic operation of customer-owned back-up generators by distribution utilities or load-serving entities. The back-up reciprocating or internal combustion engine is the most widespread form of distributed generation, demonstrating high penetration levels in commercial and industrial areas. If the load-serving entity can oversee the operation of some of these units during strategic hours, important benefits can be realized, not only for the utility, but also for the owner of the unit and the society in general as shown in the results. The most important benefits of this coordinated operation are identified and quantified, using real cost data and pricing from a real North American electricity market.     

Intelligent-Based Approach to Islanding Detection in Distributed Generation

This paper introduces a new intelligent-based approach for detecting islanding in distributed generation (DG). This approach utilizes and combines various system parameter indices in order to secure the detection of islanding for any possible network topology, penetration level and operating condition of the DG under study. Hence, every parameter index displays characteristics for a given set of events. The proposed technique uses the data-mining technology to extract information from the large data sets of these indices after they are screened off-line via massive event analyses using network simulations. The technique is tested on a typical DG with multiple distributed resources and the results indicate that this technique can successfully detect islanding operations. In addition, this technique can also overcome the problem of setting the detection thresholds inherent in the existing techniques by optimizing their settings     

Intramolecularly crosslinked macromolecules—Formation and structure,characterization and particle properties

Reactive intramolecularly crosslinked macromolecules (RICM) (reactive microgels) have been synthesized by emulsion copolymerization. Besides 1,4-divinylbenzene (1,4-DVB), self-emulsifying unsaturated polyesters (EUP) were used. In copolymerization of EUP and comonomers the diffusion rate of the latter influences the copolymerization rate of the growing species, if the initiator concentration is high and the water solubility of the difunctional comonomer is low. The compact structure of RICM is indicated by low slopes of log [\eta]/log_w. Values of [\eta] of RICM are low and their molar masses high. [\eta] depends on the structure of RICM, e.g. pendent chains and crosslink density. Structures with pendent EUP chains could be confirmed by hydrolytic degradation. RICM may be stabilized electrostatically or sterically. Network chains of RICM from 1,4-DVB are immobile.