GaAs pHEMT-based technology for microwave applications in a volume MMIC production environment on 150-mm wafers

The establishment of a 150-mm (6-in) gallium arsenide (GaAs) facility is described together with the development of very high yielding and cost-effective semiconductor device technologies and a manufacturing capacity of over 40000 wafers/annum. The background to the demand for very high volumes of RF products for this market is discussed, together with the prospects for future growth. The paper describes recent process development by the utilization of a data-driven yield management system to support the delivery of high-quality RF products to customers. Finally, "end of line" DC and RF testing of finished 150-mm GaAs pHEMT foundry wafers is described, enabling scalar measurements of power, noise, and intermodulation products as well as vector measurements of S-parameters and noise parameters at frequencies of up to 40 GHz.     

Extending the color gamut and dynamic range of an sRGB image using a residual image

Image sources, such as digital camera captures and photographic negatives, typically have more information than can be reproduced on a photographic print or a video display. The information that is lost during the tone/color rendering process relates to both the extended dynamic range and color gamut of the original scene. In conventional photographic systems, most of this additional information is archived on the photographic negative and can be accessed by adjusting the way the negative is printed. However, most digital imaging systems have traditionally archived only a rendered video RGB image. As a result, it is not possible to make the same sorts of image manipulations that historically have been possible with conventional photographic systems. This suggests that there would be an advantage to storing images using an extended dynamic range/color gamut color encoding. However, because of file compatibility issues, digital imaging systems that store images using color encoding other than a standard video RGB representation (e.g., sRGB) would be significantly disadvantaged in the marketplace. In this article, we describe a solution that has been developed to maintain compatibility with existing file formats and software applications, while simultaneously retaining the extended dynamic range and color gamut information associated with the original scenes. With this approach, the input raw digital camera image or film scan is first transformed to the scene‐referred ERIMM RGB color encoding. Next, a rendered sRGB image is formed in the usual way and stored in a conventional image file (e.g., a standard JPEG file). A residual image representing the difference between the original extended dynamic range image and the final rendered image is formed and stored in the image file using proprietary metadata tags. This provides a mechanism for archiving the extended dynamic range/color gamut information, which is normally discarded during the rendering process, without sacrificing interoperability. Appropriately enabled applications can decode the residual image metadata and use it to reconstruct the ERIMM RGB image, whereas applications that are not aware of the metadata will ignore it and only have access to the sRGB image. The residual image is formed such that it will have negligible pixel values for those portions of the image that lie within the sRGB gamut, and will therefore be highly compressible. Tests on a population of 950 real customer images have demonstrated that the extended dynamic range scene information can be stored with an average file size overhead of about 8% compared to the sRGB images alone. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 251–266, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10160     

A Hermitian Box-scheme for One-dimensional Elliptic Equations – Application to Problems with High Contrasts in the Ellipticity

We introduce a new box-scheme, called ``hermitian box-scheme' on the model of the one-dimensional Poisson problem. The scheme combines features of the box-scheme of Keller, [20], [13], with the hermitian approximation of the gradient on a compact stencil, which is characteristic of compact schemes, [9], [21]. The resulting scheme is proved to be 4th order accurate for the primitive unknown u and its gradient p. The proved convergence rate is 1.5 for (u,p) in the discrete L ² norm. The connection with a non standard mixed finite element method is given. Finally, numerical results are displayed on pertinent 1-D elliptic problems with high contrasts in the ellipticity, showing in practice convergence rates ranging from 1 to 2.5 in the discrete H ¹ norm. This work has been performed with the support of the GDR MOMAS, (ANDRA, CEA, EDF, BRGM and CNRS): Modélisation pour le stockage des déchets radioactifs. The author thanks especially A. Bourgeat for his encouragements and his interest in this work.     

Optical properties of Nd-doped Ca3(VO4)2 single crystal fiber

Optical absorption and photoluminescence of Ca₃(VO₄)₂ single crystal grown by a floating-zone technique and containing Nd³⁺ ions were investigated. High absorption coefficients and broadening of most absorption bands are present at 300 K, while substructures in some of the same bands can be evidenced at 12 K. Most features of measured spectra are characteristic of random occupation of more than a single Ca²⁺ site by the Nd³⁺ ion and of distortions provoked by different charge compensation mechanisms involving oxygen vacancies promotion in the crystal lattice. Nd³⁺ optical properties were studied by using the Judd-Ofelt theory to calculate the spectral parameters relevant for laser applications.     

Classroom learning environments and effective schooling.

Reviews the research on psychosocial aspects of classroom environment by outlining economical, hand-scorable classroom environment instruments (i.e., Classroom Environment Scale, Individualized Classroom Environment Questionnaire, a class inventory developed by the present author and colleagues [1982]) and describing their past uses. Studies on the effects of classroom environment on student outcomes, use of environment variables as process criteria in evaluating educational innovations, and teachers' practical attempts to use learning environment assessments to guide improvements in classrooms are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Plastic deformation in a multifunctional Ti-Nb-Ta-Zr-O alloy

Mechanisms for plastic deformation in the newly developed Ti-24 at. pct (Ta + Nb + V)-(Zr,Hf)-O alloys (Gum Metal) were investigated in relation to their unique properties. Transmission electron microscopy revealed that the microstructure after deformation was characterized by highly distorted crystal images, which are accompanied by numerous “giant faults.” Such plastic behavior implies that a large amount of elastic stain energy was stored discretely and hierarchically during cold working. Calculated elastic constants of the Ti-X (Nb,Ta,Mo,V) binary systems predicted that Young’s modulus in 〈001〉 and shear moduli along some directions including slip systems in a bcc crystal were extraordinary small. The low modulus not only well explains the highly distorted microstructure observed in the cold-worked specimens, but also signifies that ideal shear strength of the developed alloys is a very small value, which is close to the practical strength required for plastic deformation in the alloy. This implies that the giant faults observed in the deformed specimen were formed without the aid of dislocation glide.     

Symbolic parametrization of curves

If algebraic varieties like curves or surfaces are to be manipulated by computers, it is essential to be able to represent these geometric objects in an appropriate way. For some applications an implicit representation by algebraic equations is desirable, whereas for others an explicit or parametric representation is more suitable. Therefore, transformation algorithms from one representation to the other are of utmost importance.We investigate the transformation of an implicit representation of a plane algebraic curve into a parametric representation. Various methods for computing a rational parametrization, if one exists, are described. As a new idea we introduce the concept of working with classes of conjugate (singular or simple) points on curves. All the necessary operations, like determining the multiplicity and the character of the singular points or passing a linear system of curves through these points, can be applied to such classes of conjugate points. Using this idea one can parametrize a curve if one knows only one simple point on it. We do not propose any new method for finding such a simple point. By classical methods a rational point on a rational curve can be computed, if such a point exists. Otherwise, one can express the coordinates of such a point in an algebraic extension of degree 2 over the ground field.