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.     

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.     

Cost accounting for shared IT infrastructures

IT infrastructure, such as servers and networking equipment, accounts for a large proportion of the IT costs in modern organizations. Typically, this IT infrastructure is shared among multiple applications and customers. Cost allocation of shared IT infrastructure is difficult and regularly based on biased cost allocation keys, which often causes free-rider problems. Measuring usage is technically difficult and incurs high costs. In this paper we propose a method to derive adequate estimators for the resource consumption of a customer-oriented service. These so-called resource profiles can then provide a basis for cost allocation keys. The estimators are derived from a series of load tests, as they are typically done before an application is launched in larger organizations. Such profiles need to be unbiased and precise even in cases of varying workloads and in rather heterogeneous environments. We describe the results of a set of experiments in an infrastructure provided by the BMW Group, and illustrate how the estimation can be integrated into existing IT service management processes. In our experiments we use Queuing Networks to validate the estimated resource profiles under different workloads.     

Measurement of Spectral Properties for a Non-Gaussian Process Model of EEG

Abstract

The electrical activity of the brain produces a signal which in general is a non-stationary process. Nevertheless stationary Gaussian models are used successfully to characterize the signal in short sections without obvious non-stationarities. However, it has been observed that the characterization of the signal differs more between separate sections than may be explained using a stationary Gaussian model. In this paper a stationary but non-Gaussian process model of EEG is developed and analyzed. It is shown that for a given measurement time estimates of the autocorrelation function and the power spectrum are less accurate for this process than for the corresponding process in a Gaussian model. Upper limits for the increase in the variance of the estimates are given.

The process has been simulated on a digital computer and the experimental results verify the theoretical properties.     

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.     

Application of a new algorithm using Doppler information to retrieve complex wind fields over the Black Sea from ENVISAT SAR images

Several algorithms have been proposed to retrieve near-surface wind fields from C-band synthetic aperture radar (SAR) images acquired over the ocean. They mainly differ in the way they retrieve the wind direction. Conventionally, the wind direction is taken from atmospheric models or is extracted from the linear features sometimes visible in SAR images. Recently, a new wind retrieval algorithm has been proposed, which also includes the Doppler shift induced by motions of the sea surface. In this article, we apply three wind retrieval algorithms, including the one using Doppler information, to three complex wind events encountered over the Black Sea and compare the SAR-derived wind fields with model wind fields calculated using the high-resolution weather research and forecasting (WRF) model. It is shown that the new algorithm is very efficient in resolving the 180° ambiguity in the wind direction, which is often a problem in the streak-based wind retrieval algorithms. However, the Doppler-based algorithm only yields good results for wind directions that have a significant component in the look direction of the SAR antenna. Furthermore, it is dependent on good separation of the contributions to the Doppler shift induced by surface currents and wind-related effects (wind drift and wind-sea components of the ocean wave spectrum). We conclude that an optimum wind retrieval algorithm should consist of a combination of the algorithms based on linear features and Doppler information.