Epitaxial liftoff microcavities for 1.55-μm quantum-well spatiallight modulators

Microcavities operating at 1.55 μm have been realized according to the epitaxial liftoff (ELO) technique. The process is described and characterized. No significant variation of the optical properties of the grafted devices has been found. The technique is then applied to a spatial light modulator made by inserting a 3-μm multiple-quantum-well device in a short asymmetric Fabry-Perot microcavity. An enhancement by a factor 1000 of the performances of the switching component is obtained. The input diffraction efficiency reaches 2% in a degenerated four wave mixing configuration with a pulse energy of 1 μJ/cm² and without any applied electric field     

Empirical modeling of LF gate noise in GaAs DCFET in impactionization regime

The evolution of the 1/f gate noise in GaAs DCFET has been analyzed in the impact ionization regime. As the drain bias Vd is raised, a steep increase of the 1/f gate current noise is observed in correlation with the triggering of the impact ionization mechanism. A novel and empirical model of the 1/f low frequency gate current noise S _ig measured in the impact ionization regime is proposed. The following relation fits it with an exponential law: S_ig=E exp (-F/Vd) (1/f), which is similar to the well-known dependence of the impact ionization rate α on the drain bias     

Implementation of an Aerostat Positioning System With Cable Control

The capabilities of a multi-tethered aerostat positioning system are investigated using experimental and simulation results. The system consists of a platform supported by a helium-filled aerostat and attached to three anchored ground tethers actuated using computer-controlled winches. The experimental system was designed to perform a proof-of-concept study of a novel large-scale radio telescope requiring a receiver to be positioned accurately at an altitude of up to 500 m. Results from a series of flight tests are presented with a comparison between the passive response of the system and the response using proportional, integral, and derivative (PID) controllers with a position feedback. The motion of the platform is smaller for all cases using the feedback control. To improve on the PID results, a dynamics model of the system is used to develop and simulate optimal and feedforward (FF) control strategies. The optimal linear quadratic Gaussian (LQG) controller offers a 50% improvement over the PID controller, and both the LQG and the PID feedback controllers were shown to benefit considerably from the addition of a FF control term that exploits the measurements of the system's main disturbance force     

Efficient disparity vector prediction schemes with modified P frame for 2D camera arrays

An efficient disparity estimation algorithm for multi-view video sequences, recorded by a two-dimensional camera array in which the cameras are spaced equidistantly, is presented. Because of the strong geometrical relationship among views, the disparity vectors of a certain view can for most blocks be derived from the disparity vectors of other views. A frame constructed using that idea is called a D frame in this work. Three new prediction schemes which contain D frames are proposed for encoding 5 × 3 multi-view video sequences. The schemes are applied to several multi-view image sequences taken from a camera-array and they are compared in terms of quality, bit-rate and complexity. The experimental results show that the proposed prediction schemes significantly decrease the complexity of the encoder at a very low cost of quality and/or bit-rate.     

Radiation damage and annealing behaviour in Be+-implanted pure Ga(Al)Sb layers

Implantation of Be⁺ ions into GaAISb epilayers is used to realize thep ⁺ layer of the Ga_0.96Al_0.04Sb p⁺/Ga_0.96Al_0.04Sbn ⁻ /GaSbn ⁺ (1.55 /Μm) avalanche photodetector whose performances are detailed in Ref. (1). The GaAISb layers are grown using liquid phase epitaxy (LPE); the quality of these as-grown layers is shown through photoluminescence and channeling measurements. The last part of this paper is devoted to the damaging level in the Be⁺-implanted layers. Some annealing techniques are presented as a mean of restoration of the implanted layers. It is clear from the results that the Be⁺ ion implantation leads to a low damage level in this III-V compound.     

Equity Metrics With Risk, Performance, and Cost Objectives for the Prioritization of Transportation Projects

Prioritizing and selecting a few critical transportation projects from several competing projects is a multiobjective combinatorial optimization problem (MOCO). Transportation planners and managers are always interested in analyzing and visualizing the tradeoffs involved, but equity issues in distribution of resources are given much less attention. This paper develops a methodology for integrating equity metrics with traditional metrics for planning and prioritizing a large and diverse portfolio of transportation investment projects. The methodology serves to help planners, managers, and engineers to visualize and compare measures of the distributed equity of the allocation along with cost-benefit tradeoffs. It is based on incorporating network-level equity metrics along with traditional metrics in formulating a generic multiobjective combinatorial optimization (MOCO) problem and visualizing multiobjective tradeoffs on the spatial network. A case study of a region demonstrates the use of the methodology in tradeoff analysis for prioritizing and selecting transportation projects. The approach is adaptable to other manufacturing and service industries where consideration of the distributed equity of allocation is an important issue.     

Flexible Nanosomes (SECosomes) Enable Efficient siRNA Delivery in Cultured Primary Skin Cells and in the Viable Epidermis of Ex Vivo Human Skin

The extent to which nanoscale‐engineered systems cross intact human skin and can exert pharmacological effects in viable epidermis is controversial. This research seeks to develop a new lipid‐based nanosome that enables the effective delivery of siRNA into human skin. The major finding is that an ultraflexible siRNA‐containing nanosome—prepared using DOTAP, cholesterol, sodium cholate, and 30% ethanol—penetrates into the epidermis of freshly excised intact human skin and is able to enter into the keratinocytes. The nanosomes, called surfactant‐ethanol‐cholesterol‐osomes (SECosomes), show excellent size, surface charge, morphology, deformability, transfection efficiency, stability, and skin penetration capacity after complexation with siRNA. Importantly, these nanosomes have ideal characteristics for siRNA encapsulation, in that the siRNA is stable for at least 4 weeks, they enable highly efficient transfection of in vitro cultured cells, and are shown to transport siRNA delivery through intact human skin where changes in the keratinocyte cell state are demonstrated. It is concluded that increasing flexibility in nanosomes greatly enhances their ability to cross the intact human epidermal membrane and to unload their payload into targeted epidermal cells.     

Data-parallel intra decoding for block-based image and video coding on massively parallel architectures

With the increasing number of processor cores available in modern computing architectures, task or data parallelism is required to maximally exploit the available hardware and achieve optimal processing speed. Current state-of-the-art data-parallel processing methods for decoding image and video bitstreams are limited in parallelism by dependencies introduced by the coding tools and the number of synchronization points introduced by these dependencies, only allowing task or coarse-grain data parallelism. In particular, entropy decoding and data prediction are bottleneck coding tools for parallel image and video decoding. We propose a new data-parallel processing scheme for block-based intra sample and coefficient prediction that allows fine-grain parallelism and is suitable for integration in current and future state-of-the-art image and video codecs. Our prediction scheme enables maximum concurrency, independent of slice or tile configuration, while minimizing synchronization points. This paper describes our data-parallel processing scheme for one- and two-dimensional prediction and investigates its application to block-based image and video codecs using JPEG XR and H.264/AVC Intra as a starting point. We show how our scheme enables faster decoding than the state-of-the-art wavefront method with speedup factors of up to 21.5 and 7.9 for JPEG XR and H.264/AVC Intra coding tools respectively. Using the H.264/AVC Intra coding tool, we discuss the requirements of the algorithm and the impact on decoded image quality when these requirements are not met. Finally, we discuss the impact on coding rate in order to allow for optimal parallel intra decoding.     

Electronic transport in one-dimensional Ca3Co2O6 single crystal

The electronic conductivity study of the quasi-one-dimensional Ca₃Co₂O₆ single crystal evidences a Variable Range Hopping conductivity with temperature-induced crossover between 1D and 3D transport and the opening of a Coulomb gap in the d bands along with the ferromagnetic intra-chain ordering. A large negative magneto-resistance is observed at low temperatures. Both spin-dependent hopping and field-induced suppression of the Coulomb gap are discussed. The electronic hopping parameters we infer agree remarkably with the accessible Co sites. Finally, we present the first electronic noise study in a one-dimensional frustrated magnetic single crystal and we discuss the interplay between the low temperature 3D magnetic ordering and the spin-dependent hopping conductivity on the Co sites.