Effects of metallization thickness of ceramic substrates on the reliability of power assemblies under high temperature cycling

This study focuses on the influence of metallization thickness of ceramic substrates on reliability and lifetime of electronic power assemblies under high temperature cycling. The paper presents experimental and numerical results on different test vehicles with a number of DCB substrates with AlN ceramic and different copper thicknesses. It will be shown the influence of the DCB metallization on failure modes such as ceramic fracture and solder delamination under high temperature cycles. Finally, these samples will be compared with DCB substrates equipped with dimples and DAB substrates. Furthermore, the main factors that could increase the lifetime expectancy of power modules in such harsh environments will be identified.     

A new CAD mesh segmentation method, based on curvature tensor analysis

This paper presents a new and efficient algorithm for the decomposition of 3D arbitrary triangle meshes and particularly optimized triangulated CAD meshes. The algorithm is based on the curvature tensor field analysis and presents two distinct complementary steps: a region based segmentation, which is an improvement of that presented by Lavoue et al. [Lavoue G, Dupont F, Baskurt A. Constant curvature region decomposition of 3D-meshes by a mixed approach vertex-triangle, J WSCG 2004;12(2):245-52] and which decomposes the object into near constant curvature patches, and a boundary rectification based on curvature tensor directions, which corrects boundaries by suppressing their artefacts or discontinuities. Experiments conducted on various models including both CAD and natural objects, show satisfactory results. Resulting segmented patches, by virtue of their properties (homogeneous curvature, clean boundaries) are particularly adapted to computer graphics tasks like parametric or subdivision surface fitting in an adaptive compression objective.     

Indium Phosphide‐Based Quantum Dots with Shell‐Enhanced Absorption for Luminescent Down‐Conversion

It is shown that admixing small amounts of cadmium into the shell of InP/ZnSe core/shell quantum dots results in an increased absorption of blue light and a limited redshift of the band‐edge emission. These effects reflect the reduced bandgap of (Zn,Cd)Se alloys and their smaller conduction‐band offset with InP. Nevertheless, adjusting the InP core size enables InP/ZnSe and InP/(Zn,Cd)Se quantum dots with identical emission characteristics to be made. Processing both materials into remote phosphor disks, it is demonstrated that the shell‐enhanced absorbance of InP/(Zn,Cd)Se has the double benefit of suppressing self‐absorption and reducing the amount of quantum dots by weight needed to attain a given blue‐to‐red color conversion.     

Comparison of the fuel oil biodegradation potential of hydrocarbon-assimilating microorganisms isolated from a temperate agricultural soil

Strains of hydrocarbon-degrading microorganisms (bacteria and fungi) were isolated from an agricultural soil in France. In a field, a portion was treated with oily cuttings resulting from the drilling of an onshore well. The cuttings which were spread at the rate of 600 g HC m-2 contained 10% of fuel oil hydrocarbons (HC). Another part of the field was left untreated. Three months after HC spreading, HC adapted bacteria and fungi were isolated at different soil depths in the two plots and identified. The biodegradation potential of the isolated strains was monitored by measuring the degradation rate of total HC, saturated hydrocarbons, aromatic hydrocarbons and resins of the fuel. Bacteria of the genera Pseudomonas, Brevundimonas Sphingomonas, Acinetobacter, Rhodococcus, Arthrobacter, Corynebacterium and fungi belonging to Aspergillus, Penicillium, Beauveria, Acremonium, Cladosporium, Fusarium, and Trichoderma were identified. The most active strains in the assimilation of saturates and aromatics were Arthrobacter sp., Sphingomonas spiritivorum, Acinetobacter baumanii, Beauveria alba and Penicillum simplicissimum. The biodegradation potential of the hydrocarbon utilizing microorganisms isolated from polluted or unpolluted soils were similar. In laboratory pure cultures, saturated HC were more degraded than aromatic HC, whereas resins were resistant to microbial attack. On an average, individual bacterial strains were more active than fungi in HC biodegradation.     

Effect of hydrocarbon fractions,N2 and CO2 in feed gas on hydrogen production using sorption enhanced steam reforming: Thermodynamic analysis

H₂ yield and purity from sorption enhanced steam reforming (SE-SR) are determined by temperature, S:C ratio in use, and feed gas composition in hydrocarbons, N₂ and CO₂. Gases with high hydrocarbons composition had the highest H₂ yield and purity. The magnitude of sorption enhancement effects compared to conventional steam reforming (C-SR), i.e. increases in H₂ yield and purity, and drop in CH₄ yield were remarkably insensitive to alkane (C1C3) and CO₂ content (0.1–10 vol%), with only N₂ content (0.4–70 vol%) having a minor effect. Although the presence of inert (N₂) decreases the partial pressure of the reactants which is beneficial in steam reforming, high inert contents increase the energetic cost of operating the reforming plants. The aim of the study is to investigate and demonstrate the effect of actual shale gas composition in the SE-SR process, with varied hydrocarbon fractions, CO₂ and N₂ in the feedstock.     

Comparing single vehicle and multivehicle fatal road crashes: A joint analysis of road conditions,time variables and driver characteristics

The difference between single vehicle crashes and multivehicle crashes was investigated in a collection of fatal crashes from six European countries. Variables with respect to road conditions, time variables, and participant characteristics were studied separately at first and then jointly in a logistic multiple regression model allowing to weigh different accounts of single vehicle as opposed to multivehicle crash occurrence.     

Rapid screening of DOM's metal-binding ability using a fluorescence-based microplate assay

This note describes the development of a method to rapidly quantify the metal-binding ability of low-volume DOM samples based on their fluorescence properties. The method uses 96-well microplates to screen the fluorescence quenching observed when increasing concentrations of various metals are added to the pH-buffered DOM sample. Only 1.6 mL of DOM sample is required to quantify the binding affinity for each metal and the result is obtained in a few minutes. This study presents results for a surface soil DOM sample for which binding was assessed for Cu2+, Fe2+, Ni2+ at pH 5 and 9.     

Immunocytochemical analysis of connexin expression in the healthy and diseased cardiovascular system

Gap junctions play essential roles in the normal function of the heart and arteries, mediating the spread of the electrical impulse that stimulates synchronized contraction of the cardiac chambers, and contributing to co-ordination of activities between cells of the arterial wall. In common with other multicellular systems, cardiovascular tissues express multiple connexin isotypes that confer distinctive channel properties. This review highlights how state-of-the-art immunocytochemical and cellular imaging techniques, as part of a multidisciplinary approach in gap junction research, have advanced our understanding of connexin diversity in cardiovascular cell function in health and disease. In the heart, spatially defined patterns of expression of three connexin isotypes-connexin43, connexin40, and connexin45-underlie the precisely orchestrated patterns of current flow governing the normal cardiac rhythm. Derangement of gap junction organization and/or reduced expression of connexin43 are associated with arrhythmic tendency in the diseased human ventricle, and high levels of connexin40 in the atrium are associated with increased risk of developing atrial fibrillation after coronary by-pass surgery. In the major arteries, endothelial gap junctions may simultaneously express three connexin isotypes, connexin40, connexin37, and connexin43; underlying medial smooth muscle, by contrast, predominantly expresses connexin43, with connexin45 additionally expressed at restricted sites. In normal arterial smooth muscle, the abundance of connexin43 gap junctions varies according to vascular site, and shows an inverse relationship with desmin expression and positive correlation with the quantity of extracellular matrix. Increased connexin43 expression between smooth muscle cells is closely linked to phenotypic transformation in early human coronary atherosclerosis and in the response of the arterial wall to injury. Current evidence thus suggests that gap junctions in both their guises, as pathways for cell-to-cell signaling in the vessel wall and as pathways for impulse conduction in the heart, contribute to the initial pathogenesis and eventual clinical manifestation of human cardiovascular disease.     

Terahertz Emission in Asymmetric Quantum Wells by Frequency Mixing of Midinfrared Waves

Generation of terahertz (THz), and sub-THz, coherent waves has been demonstrated at room temperature in GaAs-AlGaAs asymmetric quantum wells by mixing two CO₂ laser beams. Two overlapping regimes were studied: the double resonance regime where three states are involved and the optical rectification which relies on two states only. The measured conversion efficiency of ~10^-7 W^-1 is in reasonable agreement with theoretical predictions. In addition, this technique of THz generation provides a model system to study the emission profile from an ensemble of radiating dipoles. For instance, backward emission and strong diffraction effects have been observed     

Pixelless thermal imaging with integrated quantum-well infraredphotodetector and light-emitting diode

A large pixelless thermal imager based on the epitaxial integration of a GaAs-AlGaAs quantum-well infrared photodetector and a GaAs light-emitting diode is demonstrated. The device transforms a mid-infrared (9 μm) scene to a near-infrared (0.82 μm) emission image with a temperature resolution of ~1 K, limited by the integration capacity of the near-visible camera