Rate Control Algorithms for Non-Embedded Wavelet-Based Image Coding

During the last decade, there has been an increasing interest in the design of very fast wavelet image encoders focused on specific applications like interactive real-time image and video systems, running on power-constrained devices such as digital cameras, mobile phones where coding delay and/or available computing resources (working memory and power processing) are critical for proper operation. In order to reduce complexity, most of these fast wavelet image encoders are non-(SNR)-embedded and as a consequence, precise rate control is not supported. In this work, we propose some simple rate control algorithms for these kind of encoders and we analyze their impact to determine if, despite their inclusion, the global encoder is still competitive with respect to popular embedded encoders like SPIHT and JPEG2000. In this study we focus on the non-embedded LTW encoder, showing that the increase in complexity due to the rate control algorithm inclusion, maintains LTW competitive with respect to SPIHT and JPEG2000 in terms of R/D performance, coding delay and memory consumption.     

The mechanical behavior of silicon during small-scale indentation

The mechanical behavior of crystalline silicon during small-scale indentation has been studied using a Nanoindenter. Tests were performed on bothp-type andn-type materials in the (100), (110), and (111) orientations at peak loads ranging from 0.5 to 120 mN. The indentation load-displacement curves exhibit two features which appear to be unique to silicon. First, at large peak loads, a sharp discontinuity in displacement is observed as the indenter is unloaded. Second, at small peak loads, a large, non-degenerative hysteresis is exhibited. Possible mechanistic origins for the discontinuity and hysteresis are discussed.     

Approaches to the manipulation of mammary involution

Mammary involution is a gradual process that occurs following cessation of milking. Regression of mammary secretory tissue accompanies dramatic changes in secretion composition during the transition from lactation to involution. Conversely, rapid differentiation of secretory tissue and copious accumulation of colostrum occur as parturition approaches. The duration of the nonlactating period, mammary gland health, and secretory cell response to hormones influence subsequent lactational performance in most species. Manipulation of the bovine mammary gland in an attempt to hasten involution has been studied. The primary objective of these studies was to determine if hastened involution would decrease new intramammary infections during the early nonlactating period. Results of these studies have also led to a more fundamental understanding of events that occur during physiological transition of the mammary gland. Adequate regression, proliferation, and differentiation of mammary secretory epithelium during the nonlactating period of ruminants appear to be essential for maximal milk production during lactation. Factors that interfere with these mechanisms can adversely affect mammary function during the impending lactation. A greater understanding of these processes may provide new approaches for increasing milk production in dairy cattle.     

Minimization of leakage current of recessed gate AlGaN/GaN HEMTs by optimizing the dry-etching process

The backward current of Schottky contacts on unintentionally doped GaN samples prepared by different dry-etching methods was investigated. It was found that an ion beam etching (IBE) process with an accelerating voltage of 250 V under an angle of 20 degrees to minimize channeling achieves the best results. The backward current in this case is 4 × 10⁻¹⁰ A/μm² compared to the backward current of the unetched sample of 1 × 10⁻⁷ A/μm² at −100 V. With this process, recessed gate HEMTs on AlGaN/GaN heterostructures grown by low pressure MOVPE were fabricated and compared to HEMTs without recess. The applied gate recess etching technique improves the leakage current by nearly a factor of two. The maximum transconductance is improved from 40 mS/mm to 60 mS/mm at a gate length of 4 μm.     

Microstructural characterisation of nanocrystalline GaN prepared by detonations of gallium azides

High quality nanoscale, phase-pure hexagonal gallium nitride (GaN) crystallites have been synthesized by the thermal induced detonation of molecular precursors of the type (R₃N)Ga(N₃)₃ (R=CH₃, C₂H₅, etc.). The method allows the control of the particle size regime from 2 to about 1000 nm. X-ray diffraction and Rietveld simulations revealed an anisotropic platelet-like shape of the particles. The obtained GaN material was as well characterized by transmission electron microscopy and electron diffraction, photoluminescence spectroscopy, SEM, IR, RAMAN, thermal gas effusion/mass spectrometry, thermal analysis, elemental analysis. Gas absorption measurements (BET method) showed a specific surface area of about 90 m² · g⁻¹. © 1998 John Wiley & Sons, Ltd.     

Analysis of the interaction of adjacent layers of a GFRP-laminate under fatigue loading

A layer-wise strength analysis of laminates leads to realistic results not only with quasistatic but also with cyclic loading. The used fatigue strength has to be determined by experiment. Degradation models exist, used to reduce the laminate stiffness due to inter-fibre fracture (IFF) cracks. However a notch effect caused by IFF – in other words, a local increase in stress in the laminate adjacent to the laminate affected by an IFF – is not included. This leads to a premature failure of the laminate much earlier as it is predicted by a failure criteria. Performing 3-point-bending tests the notch effect was measured to obtain a more exact service life prediction. Adequate crack arresting layers are tested which will reduce the negative notch effect.     

Hybrid organic/inorganic molecular heterojunctions based on strained nanomembranes

In this work, we combine self-assembly and top-down methods to create hybrid junctions consisting of single organic molecular monolayers sandwiched between metal and/or single-crystalline semiconductor nanomembrane based electrodes. The fabrication process is fully integrative and produces a yield loss of less than 5% on-chip. The nanomembrane-based electrodes guarantee a soft yet robust contact to the molecules where the presence of pinholes and other defects becomes almost irrelevant. We also pioneer the fabrication and characterization of semiconductor/molecule/semiconductor tunneling heterojunctions which exhibit a double transition from direct tunneling to field emission and back to direct tunneling, a phenomenon which has not been reported previously.     

Doping of graphene exfoliated on SrTiO3

We present atomic force microscopy and scanning Kelvin probe data obtained under ultra-high vacuum conditions from graphene exfoliated on crystalline SrTiO(3) substrates. The contact potential difference shows a monotonic increase with the number of graphene layers until after five layers of saturation is reached. By identifying the saturation value with the work function of graphite we determine the work function of single and bilayer graphene to be Φ(SLG) = 4.409 ± 0.039 eV and Φ(BLG) = 4.516 ± 0.035 eV, respectively. In agreement with the higher work function of single-layer graphene with respect to free-standing graphene, our measurements indicate an accumulation of charge carriers corresponding to a doping of the exfoliated graphene layer with electrons.     

Magnetic materials and devices for the 21st century: stronger, lighter, and more energy efficient

A new energy paradigm, consisting of greater reliance on renewable energy sources and increased concern for energy efficiency in the total energy lifecycle, has accelerated research into energy-related technologies. Due to their ubiquity, magnetic materials play an important role in improving the efficiency and performance of devices in electric power generation, conditioning, conversion, transportation, and other energy-use sectors of the economy. This review focuses on the state-of-the-art hard and soft magnets and magnetocaloric materials, with an emphasis on their optimization for energy applications. Specifically, the impact of hard magnets on electric motor and transportation technologies, of soft magnetic materials on electricity generation and conversion technologies, and of magnetocaloric materials for refrigeration technologies, are discussed. The synthesis, characterization, and property evaluation of the materials, with an emphasis on structure-property relationships, are discussed in the context of their respective markets, as well as their potential impact on energy efficiency. Finally, considering future bottlenecks in raw materials, options for the recycling of rare-earth intermetallics for hard magnets will be discussed.