Studies for the construction of the 100 m telescope

Construction of 100-M telescope for radio astronom

Predictions of NOx emissions in pulverized coal combustion.

The purpose of this research work was to develop a transferable mathematically simple model which gives the possibility to make fast and easy predictions regarding the NOx emission behavior of a broad–spectrum of coals within a certain combustion environment. In this context, this thesis is a further step of a common ongoing investigation focused on predicting NOx emissions from self–sustaining, pulverized coal combustion in dry bottom firing systems. A comprehensive literature research focused on already published NOx prediction approaches from scientific publications based on fundamental quantitative relationships or empirical algorithms and statistical relationships was also carried out in this context. This research concentrated on three specific areas which were found to constitute a major gap in the knowledge of NOx formation in industrial full–scale applications: the fuel properties; the dependence of furnace geometry factors; and the specific operating conditions. The developed model shows a strong statistical significance with a coefficient of determination of 0.9876 and a standard error of 28 mg / m³ STPdry at 6 % O2 based on 142 observations coming from 28 utility boilers. Direct comparisons between model history and observations reported by other researchers have also shown very good conformities. For that background, this thesis form a good basis for identifying individual factors which contributes to system related NOx emissions in order to investigate how variations in the process parameters affect the emission level. Perhaps, as contribution to the understanding of NOx formation during coal combustion what is still an imperfectly understood phenomenon, or as basis for possible process optimization which might find application on pulverized coal–fired boilers to make the world a little bit more green

Merging of the alpha and beta relaxations and aging via the Johari–Goldstein modes in rapidly quenched metallic glasses

This paper provides evidence that the physical aging of deeply and rapidly quenched metallic glasses is promoted by the Johari–Goldstein slow beta relaxation, resulting in a significant irreversible increase in the mechanical modulus on initial heating. Dynamic mechanical analysis has been used to characterize relaxation phenomena of a strong and a fragile metallic glass. In addition, we can extrapolate the temperature dependence of beta- and alpha-relaxation peaks to higher temperatures and calculate the merging temperature for both types of glasses

Rezension: MARCUS HERNIG (2000), China und die interkulturelle Germanistik: Kulturvergleich,Interkulturalität und Interdisziplinarität im Rahmen der chinesischen „Wissenschaft vom Deutschen“. Einzelfallstudien zur Situation u. Entwicklung d. chinesischen Germanistik

Marcus Hernig verfolgt in seiner Studie die Fragen, wie sich die Situation der chinesischen Germanistik zur Zeit darstellt und welche kulturvergleichenden, interkulturellen und interdisziplinären Elemente in deren Lehre und Forschung bereits eingegangen sind oder geeignete Ansätze bilden könnten. Der Autor beschränkt sich dabei bewusst auf das „Hauptfachstudium der deutschen Sprache, Literatur und Landeskunde“ (S. 14) und schließt den „weiteren Bereich des Deutsch als Fremdsprache-Studiums in studienbegleitenden Kursen oder in Intensivkursen“ (ebd.) aus. Germanistik als Hauptstudienfach gab es in China 1997 an rund 25 Hochschulen mit insgesamt ca. 1600 Studierenden, Deutsch als Fremdsprache in verschiedenen Kursformen wurde an 116 Hochschulen mit mehr als 16.000 Teilnehmern unterrichtet (S. 137). Die Zahlen dürften sich nicht wesentlich verändert haben

On what Terms and why the Thermodynamic Properties of Polymer Solutions Depend on Chain Length up to the Melt

Theoretical considerations based on chain connectivity and conformational variability of polymers have lead to an uncomplicated relation for the dependence of the Flory-Huggins interaction parameter, chi, on the volume fraction of the polymer, phi, and on its number of segments, N. The validity of this expression is being tested extensively by means of vapor pressure measurements and inverse gas chromatography (complemented by osmotic and light scattering data from literature) for solutions of poly(dimethylsiloxane) in the thermodynamically vastly different solvents n-octane (n-C8), toluene (TL), and methylethylketone (MEK) over the entire range of composition for at least six different molecular masses of the polymer. The new approach is capable to model the measured chi (phi, N) very well, irrespective of the thermodynamic quality of the solvent, in contrast to traditional expressions, which are often restricted to good solvents but fail for bad ones and vice versa. At constant polymer concentration the chi values result lowest for n-C8 (best solvent) and highest for MEK (theta solvent); the data for TL fall between. The influences of N depend strongly on the thermodynamic quality of the solvent and are not restricted to dilute solutions. For good solvents chi increases with rising N. The effect is most pronounced for n-C8, where the different curves for chi (phi) fan out considerably. The influences of N become less distinct for TL, and for MEK they vanish at the (endothermal) theta temperature. For worse than theta conditions, the chi values of the long chains become less than that of short ones. This change in the sign of N-influences is in agreement with the present concept of conformational relaxation

Security Pricing in Reaction to Changes in Investor Attitudes, Governance and Regulation

The financial crisis that began in the summer of 2007 changed many aspects of the financial world. On the one hand, governing regulatory bodies around the globe introduced rules and regulations, with the goal of preventing another financial crisis of similar dimensions. On the other hand, investors changed their investment style. Structured products, viewed as one of the causes of the recent financial crisis, suffered severely. At the same time the demand for sustainable and climate related products rises massively. This thesis analyses the pricing of a variety of instruments (Bonds, Stocks, CDS, ABS and CLOs) in the aftermath of the recent financial crisis. Special attention is drawn upon the impact of changes in investor attitudes and regulatory changes on the pricing of the analyzed financial instruments

A census with ROSAT of low-luminosity X-ray sources in globular clusters

I analyze 101 observations from the ROSAT archive to search for X-ray sources in or near 55 globular clusters. New sources are found in the cores of NGC362 (a double source), NGC6121 (marginally significant), NGC6139, and NGC6266; and outside the cores of NGC6205, NGC6352 and NGC6388. More accurate positions are determined for the X-ray sources in some ten clusters. The improved position for the source in NGC6341 excludes the suggested ultraviolet counterpart. It is shown that one of the two sources reported near the core NGC6626 is spurious, as is the detection of a pulsar period in the PSPC data of this cluster; the central source is resolved in three sources. One source reported previously in NGC6304 is demoted to an upper limit. For 20 cluster cores better upper limits to the X-ray luminosity are obtained. From a statistical analysis I argue that several sources outside the cluster cores may well belong to the clusters. All spectral energy distributions observed so far are relatively soft, with bremsstrahlung temperatures =~0.9keV; there is evidence however that bremsstrahlung spectra do not correctly describe the spectra. The X-ray luminosity per unit mass for the cluster as a whole does not depend on the concentration; the luminosity per unit mass for the core may increase with the cluster concentration.Comment: 24 pages, 8 figures, 5 tables, accepted for publication in Astronomy and Astrophysic

Submillimeter and X-ray observations of an X Class flare

The GOES X1.5 class flare that occurred on August 30,2002 at 1327:30 UT is one of the few events detected so far at submillimeter wavelengths. We present a detailed analysis of this flare combining radio observations from 1.5 to 212 GHz (an upper limit of the flux is also provided at 405 GHz) and X-ray. Although the observations of radio emission up to 212 GHz indicates that relativistic electrons with energies of a few MeV were accelerated, no significant hard X-ray emission was detected by RHESSI above ~ 250 keV. Images at 12--20 and 50--100 keV reveal a very compact, but resolved, source of about ~ 10" x 10". EUV TRACE images show a multi-kernel structure suggesting a complex (multipolar) magnetic topology. During the peak time the radio spectrum shows an extended flatness from ~ 7 to 35 GHz. Modeling the optically thin part of the radio spectrum as gyrosynchrotron emission we obtained the electron spectrum (spectral index delta, instantaneous number of emitting electrons). It is shown that in order to keep the expected X-ray emission from the same emitting electrons below the RHESSI background at 250 keV, a magnetic field above 500 G is necessary. On the other hand, the electron spectrum deduced from radio observations >= 50 GHz is harder than that deduced from ~ 70 - 250 keV X-ray data, meaning that there must exist a breaking energy around a few hundred keV. During the decay of the impulsive phase, a hardening of the X-ray spectrum is observed which is interpreted as a hardening of the electron distribution spectrum produced by the diffusion due to Coulomb collisions of the trapped electrons in a medium with an electron density of n_e ~ 3E10 - 5E10 cm-3.Comment: Accpeted in Astronomy & Astrophysics. 9 Pages, 6 Figures ADDED REFERENCE