Einfluß der Schrottvorwärmung mit Erdgas und Sauerstoff im Konverter auf den Sauerstoffumsatz des LD-Verfahrens

Stand der Erkenntnisse und Ziel der eigenen Versuche. Anlagenbeschreibung und Betriebsbeobachtungen. Untersuchung der Schlackenbildung während der Schrottvorwärmung. Änderungen der Roheisenzusammensetzung durch Reaktionen mit den Vorwärmschlacken. Betrachtungen zur Sauerstoffbilanz.     

Equivalent circuit for injection-locked negative-resistance oscillators

Calculations are carried out for a van der Pol type oscillator with external force. It is illustrated how the condition of synchronisation is changed when (i) the admittance of the microwave diode is assumed to consist of an additional voltage-dependent susceptance and (ii) the frequency-determining resonator has a series reactance.     

Two software tools for plane-wave scattering on nonspherical particles in the German Aerospace Center's Virtual Laboratory

We present the methodological background, the range of applicability, and the on-line usage of two software packages, MIESCHKA and CYL, which we have developed for light-scattering analysis on nonspherical particles. MIESCHKA solves Maxwell's equations in a rigorous way but is restricted to axisymmetric geometries, whereas CYL is an approximation for finite columns with nonspherical cross sections. We have established an easy on-line access to both of these programs through the Virtual Laboratory. Its generic software infrastructure was designed to simplify the web-based usage and to support the intercomparability of scientific software.     

Assessing forest fire as a potential PCDD/F source in Queensland, Australia

Forest fires are suggested as a potential and significant source of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs), even though no studies to date provide sufficient evidence to confirm forest fires as a source of PCDD/Fs. Recent investigations in Queensland, Australia have identified a widespread contamination of PCDDs (in particular OCDD) in soils and sediments in the coastal region from an unknown source of PCDD/Fs. Queensland is predominately rural; it has few known anthropogenic sources of PCDD/Fs, whereas forest fires are a frequent occurrence. This study was conducted to assess forest fires as a potential source of the unknown PCDD/F contamination in Queensland. A combustion experiment was designed to assess the overall mass of PCDD/Fs before and after a simulated forest fire. The results from this study did not identify an increase in sigmaPCDD/Fs or OCDD after the combustion process. However, specific non-2,3,7,8 substituted lower chlorinated PCDD/Fs were elevated after the combustion process, suggesting formation from a precursor. The results from this study indicate that forest fires are unlikely to be the source of the unknown PCDD contamination in Queensland, rather they are a key mechanism for the redistribution of PCDD/Fs from existing sources and precursors.     

Graph separators: a parameterized view

Graph separation is a well-known tool to make (hard) graph problems accessible to a divide-and-conquer approach. We show how to use graph separator theorems in combination with (linear) problem kernels in order to develop fixed parameter algorithms for many well-known NP-hard (planar) graph problems. We coin the key notion of glueable select&verify graph problems and derive from that a prospective way to easily check whether a planar graph problem will allow for a fixed parameter algorithm of running time for constant c. One of the main contributions of the paper is to exactly compute the base c of the exponential term and its dependence on the various parameters specified by the employed separator theorem and the underlying graph problem. We discuss several strategies to improve on the involved constant c.     

Classification of rheumatoid joint inflammation based on laser imaging

We describe a classification system for a novel imaging method for arthritic finger joints. The basis of this system is a laser imaging technique which is sensitive to the optical characteristics of finger joint tissue. From the laser images acquired at baseline and follow-up, finger joints can automatically be classified according to whether the inflammatory status has improved or worsened. To perform the classification task, various linear and kernel-based systems were implemented and their performances were compared. Based on the results presented in this paper, we conclude that the laser-based imaging permits a reliable classification of pathological finger joints, making it a sensitive method for detecting arthritic changes.     

Coded excitation with spectrum inversion (CEXSI) for ultrasound array imaging

In this paper, a scheme called coded excitation with spectrum inversion (CEXSI) is presented. An established optimal binary code whose spectrum has no s and possesses the least variation is encoded as a burst for transmission. Using this optimal code, the decoding filter can be derived directly from its inverse spectrum. Various transmission techniques can be used to improve energy coupling within the system pass-band. We demonstrate its potential to achieve excellent decoding with very low (<80 dB) side-lobes. For a 2.6 /spl mu/s code, an array element with a center frequency of 10 MHz and fractional bandwidth of 38%, range side-lobes of about 40 dB have been achieved experimentally with little compromise in range resolution. The signal-to-noise ratio (SNR) improvement also has been characterized at about 14 dB. Along with simulations and experimental data, we present a formulation of the scheme, according to which CEXSI can be extended to improve SNR in sparse array imaging in general.     

An InGaP/GaAs Merged HBT-FET (BiFET) Technology and Applications to the Design of Handset Power Amplifiers

The last decade has seen GaAs HBTs emerge as the dominant technology in wireless handset power amplifiers. Modern application requirements and size limitations have driven industry leaders towards the co-integration of depletion mode n-FET and GaAs HBT. The merger of Bipolar and FET, or BiFET, gives an additional degree of freedom in the design of advanced power amplifiers independent of a silicon controller. This paper provides an overview of the various techniques that can be used to join the two device technologies and then shows how a merged epitaxial structure, where an FET is formed in the emitter layers of an HBT, combines functional versatility with the high volume manufacturability needed to supply millions of power amplifiers at low cost. A large-signal model of the FET structure is developed which takes into account the unique physics and geometries of the device, including voltage-dependant parameters and charges on all four electrical terminals. Specific handset applications that can benefit or be enabled by BiFET are presented, such as on-off switching, low voltage bias controllers , Auto-Bias power amplifiers, and bias circuits with low or no voltage reference. When npn-only bias circuitry is limited to low voltage reference levels, HBT power amplifiers with BiFET bias stages are shown to have superior RF performance to their npn-only counterparts.     

Rotation Averaging

This paper is conceived as a tutorial on rotation averaging, summarizing the research that has been carried out in this area; it discusses methods for single-view and multiple-view rotation averaging, as well as providing proofs of convergence and convexity in many cases. However, at the same time it contains many new results, which were developed to fill gaps in knowledge, answering fundamental questions such as radius of convergence of the algorithms, and existence of local minima. These matters, or even proofs of correctness have in many cases not been considered in the Computer Vision literature. We consider three main problems: single rotation averaging, in which a single rotation is computed starting from several measurements; multiple-rotation averaging, in which absolute orientations are computed from several relative orientation measurements; and conjugate rotation averaging, which relates a pair of coordinate frames. This last is related to the hand-eye coordination problem and to multiple-camera calibration.