Bridging and Nonbridging Oxygen Atoms in Alkali Aluminosilicate Glasses

Thallium-probe ion luminescence spectroscopy and X-ray photoelectron spectroscopy were used to study the structure of sodium aluminosilicate glasses. It was demonstrated that the O1s spectral envelope for these glasses is comprised of three energetically distinct peaks, two attributed to bridging oxygen atoms (Si-O-Si and Al-O-Si) and one to nonbridging oxygen atoms (Si-O-Na). Both techniques indicate that nonbridging oxygen atoms are present in all sodium aluminosilicate glasses, for which A1 /Na is < 1.     

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Defect recognition in crystalline silicon solar cells by X‐ray tomosynthesis with layer resolution

The increasing demand for higher quality in solar cell production led to the development of several inline control methods. Beneath the image‐guided methods, X‐ray is not yet very well investigated for the application in photovoltaic research but shows high potential. In contrast to the ordinary X‐ray radioscopic method, the tomosynthesis technique exhibits additional depth information of the solar cells and modules. In this article, several applications of tomosynthesis for the investigation of solar cells and modules are studied. It will be shown what potential the application of X‐ray and especially tomosynthesis has as quality control tool for photovoltaics. Copyright © 2013 John Wiley & Sons, Ltd.     

Kombinierte Herkunftsbestimmung der Wässer im Jökulsáá Fjöllum-Canyon (NE-Island)

The northeastern region of Iceland is characterized by dreary stony deserts and marshland with the exception of the areas Hólmatungur and Forvö in the Jökulsáá Fjöllum-canyon. The rich vegetation and the high density of springs are exceptional in this region. Since many fissure swarms run through the catchment of the Jökulsáá Fjöllum and inside the canyon there are springs with discharges over 300 l/s, it was necessary to investigate the origin of the water in both spring areas. In a field campaign the physicochemical parameters from over hundred springs were measured, samples were taken and analyzed for their water contents and isotopical parameters. Through the combination of interpolated species distibutions with measured fissures and joints and the usage of the index-species sulphate and total-boron to detect geothermal influences and chloride and δ ¹⁸ O, which shows a dependence on the continental effect, it was possible to separate springs with geothermal influences from water of uninfluenced catchments.     

Performance of TES X-ray Microcalorimeters with AC Bias Read-Out at MHz Frequencies

At SRON we are developing Frequency Domain Multiplexing for the read-out of superconducting transition edge sensor microcalorimeters for future X-ray astrophysical missions. We will report on the performance of Goddard Space Flight Center pixels under AC bias in the MHz frequency range. Superconducting flux transformers are used to improve the impedance matching between the low ohmic TESs and the SQUID. We connected 5 pixels to the LC filters with resonant frequencies ranging between 1 and 5 MHz. For X-ray photons of 6 keV we measured a best X-ray energy resolution of 3.6 eV at 1.4 MHz, consistent with the integrated Noise Equivalent Power. In addition, we improved the electrical circuit by optimizing the coupling ratio of the impedance matching transformer. In addition, we improved electrical circuit for impedance matching; modified transformer coupling ratio. As a result, we got the integrated noise equivalent power resolution of 2.7 eV at 2.5 MHz. A characterization of the detector response as a function of the AC bias voltage, bias frequency and the applied magnetic field is presented.     

Stromrichter an Netzen mit begrenzter Kurzschlußleistung

Übersicht Die klassische Theorie der Stromrichter gründet sich auf die Vorstellung eines Wechselstromnetzes, dessen Spannung am Stromrichteranschluß nicht durch den Stromrichterbetrieb beeinflußbar ist. Damit wird eine unendlich große oder praktisch jedenfalls große Netzkurzschlußleistung im Vergleich zur Stromrichterleistung vorausgesetzt. Gleichstromleistungen bei Hochspannungsübertragungen, wie sie hente vorkommen, und auch der Wunsch, bedeutende Leistungsbeträge relativ schwachen Netzen zuzuführen, haben die Grundlage für die genannte theoretische Voraussetzung mehr und mehr in Frage gestellt. In [1] werden einige Gesichtspunkte des Zusammenhanges zwischen Netzkurzschlußeleistung und Stromrichterbetrieb behandelt und die vorliegende Arbeit soll eine Weiterführung dieser Untersuchung geben. Insbesondere wird die geringste Netzkurzschlußleistung bestimmt, die gerade noch die Überführung der nominellen Anlagenleistung wenigstens grundsätzlich gestattet.

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Converters on networks with limited short-circuit capacity

Contents The classical converter theory is based on the conception of an alternating current network with a voltage at the converter connection point which cannot be influenced by the operating conditions of the converter. This means an infinite or in any case a practically large short-circuit capacity of the network compared with the power of the converter. The magnitude of power occurring in high voltage DC-transmissions today and also the requirement to supply relatively weak networks with quite great amounts of power have more and more removed the basis of the said theoretical assumption. Some points of view regarding the connection of network short-circuit capacity and converter operation are given in [1]. The present paper continues these investigations. Especially the lowest network short-circuit capacity is determined which — at least in principle — just allows the transmission of the nominal power of the plant.

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Definitionen U _N Netzwechselspannung am Stromrichteranschluß - U _NO 19^* Vom Stromrichter aus gesehene Wechselspannung hinter der transienten Netzreaktanz (X _N ) - S Scheinleistung der Grundwelle in der Verbindung Stromrichter-Filter - cos zuS gehörender Leistungsfaktor - Winkel zwischen den SpannungenU _N undU _NO - Index _m Nomineller Wert - transiente Netzkurszchlußleistung bezogen auf Netzspannung am Stromrichter - kapazitive Nennleistung eines Kondensators oder Filters am Stromrichteranschluß - D Gleichspannung - D _iO =kU _N ideelle Leerlaufgleichspannung mitU _N als Basis - D _iOO =kU _NO ideelle Leerlaufgleichspannung mitU _NO als Basis - D _i ideelle Gleichspannung (ohne Ohmschen Gleichspannungsabfall) - I Gleichstrom - Zündwinkel - Löschwinkel - d _x (d _r ) relativer induktiver (Ohmscher) Gleichspannungsabfall - - N - N ₀ - X - x - Y - y - Z - z - - Y - X - N      

Combining convergence and diversity in evolutionary multiobjective optimization

Over the past few years, the research on evolutionary algorithms has demonstrated their niche in solving multiobjective optimization problems, where the goal is to find a number of Pareto-optimal solutions in a single simulation run. Many studies have depicted different ways evolutionary algorithms can progress towards the Pareto-optimal set with a widely spread distribution of solutions. However, none of the multiobjective evolutionary algorithms (MOEAs) has a proof of convergence to the true Pareto-optimal solutions with a wide diversity among the solutions. In this paper, we discuss why a number of earlier MOEAs do not have such properties. Based on the concept of epsilon-dominance, new archiving strategies are proposed that overcome this fundamental problem and provably lead to MOEAs that have both the desired convergence and distribution properties. A number of modifications to the baseline algorithm are also suggested. The concept of epsilon-dominance introduced in this paper is practical and should make the proposed algorithms useful to researchers and practitioners alike.