Growth Techniques for Bulk ZnO and Related Compounds

ZnO bulk crystals can be grown by several methods. 1) From the gas phase, usually by chemical vapor transport. Such CVT crystals may have high chemical purity, as the growth is performed without contact to foreign material. The crystallographic quality is often very high (free growth). 2) From melt fluxes such as alkaline hydroxides or other oxides (MoO3, V2O5, P2O5, PbO) and salts (PbCl2, PbF2). Melt fluxes offer the possibility to grow bulk ZnO under mild conditions (<1000 deg. C, atmospheric pressure), but the crystals always contain traces of solvent. The limited purity is a severe drawback, especially for electronic applications. 3) From hydrothermal fluxes, usually alkaline (KOH, LiOH) aqueous solutions beyond the critical point. Due to the amphoteric character of ZnO, the supercritical bases can dissolve it up to several per cent of mass. The technical requirements for this growth technology are generally hard, but this did not hinder its development as the basic technique for the growth of {\alpha}-quartz, and meanwhile also of zinc oxide, during the last decades. 4) From pure melts, which is the preferred technology for numerous substances applied whenever possible, e.g. for the growth of silicon, gallium arsenide, sapphire, YAG. The benefits of melt growth are (i) the high growth rate and (ii) the absence of solvent related impurities. In the case of ZnO, however, it is difficult to find container materials that are compatible from the thermal (fusion point Tf = 1975 deg. C) and chemical (required oxygen partial pressure) point of view. Either cold crucible (skull melting) or Bridgman (with reactive atmosphere) techniques were shown to overcome the problems that are inherent to melt growth. Reactive atmospheres allow to grow not only bulk ZnO single crystals, but also other TCOs such as {\beta}-Ga2O3 and In2O3.Comment: 10 pages, 7 figures, talk on MRS Fall 2011 Bosto

Innovative Fortbildung der Lehrerinnen und Lehrer an beruflichen Schulen. Gutachten zum Programm

Mit der vorliegenden Expertise soll die Programmskizze für das BLK-Programm "Innovative Fortbildung der Lehrer und Lehrerinnen an beruflichen Schulen" ausdifferenziert werden. Aufgabe der Expertengruppe war es, die in der Programmskizze benannten Aufgabenfelder aufzugreifen, zu ergänzen und daraus thematische Schwerpunkte zu erarbeiten, die zugleich Empfehlungen für Maßnahmebereiche und mögliche Länderprojekte darstellen. Dabei sind die Autoren von dem Phasenmodell der KMK-Rahmenvereinbarung über die Ausbildung und Prüfung für ein Lehramt der Sekundarstufe II (berufliche Fächer) oder für berufliche Schulen vom 12. Mai 1995 ausgegangen und haben sich auftragsgemäß auf die 2. und 3. Phase beschränkt. Gliederung: 0. Konkretisierung des Auftrages. - 1. Leitbild der Entwicklung der Lehrerpersönlichkeit. - 2. Anforderungsprofil der Lehrkräfte an beruflichen Schulen. - 3. Bezugspunkte und Leitorientierungen einer innovativen Lehrerfortbildung (3.1 Berufsbiografische Phasen der Lehrerbildung. - 3.2 Gestaltungsgrundsätze in den berufsbiografischen Phasen. - 3.3 Aktuelle thematische Brennpunkte). - 4. Maßnahmebereiche für das Modellversuchsprogramm (4.1 Neue Qualifizierungs- und Lernkonzepte in der 2. Phase der Lehrerausbildung (Referendariat). - 4.2 Innovative Fortbildungsstrategien für die 3. Phase der Qualifizierung (Lernen im Beruf). - 4.3 Zusammenfassende Übersicht zu Maßnahmebereichen und Untersuchungsfeldern). - 5. Empfehlungen zur Programmorganisation, zu Projektstrukturen sowie zum Ergebnistransfer. (HoF/Text übernommen

Abschlussbericht des BLK-Programmträgers zum Modellversuchsprogramm "Innovative Fortbildung der Lehrerinnen und Lehrer an beruflichen Schulen"

Ziel des Programms war die Verbesserung der Qualifizierung der Berufsschullehrer in der 2. (Vorbereitungsdienst/Studienseminar) und 3. Phase (berufsbegleitende Fortbildung), da hierdurch notwendige Veränderungen schnell und direkt in die beruflichen Schulen eingebracht werden können. Insbesondere erprobte Innovationen aus berufsschulischen BLK-Modellversuchen wurden in die Lehrerfortbildung und in den Vorbereitungsdienst transferiert und dadurch verbreitet und umgesetzt. Programmschwerpunkte waren besondere Fragen des Vorbereitungsdienstes (z.B. Qualifizierung von "Seiteneinsteigern" für den Schuldienst, der Seminarleiter und Fachleiter, der Mentoren und Ausbildungslehrer, Bewertung von Lehrproben) und Lehrerfortbildung in Verbindung mit der Schnittstelle zum Vorbereitungsdienst (Unterrichtsgestaltung, Berufliche Schulen im Berufsbildungssystem, Organisation der Lehrerqualifizierung). Der Abschlussbericht beschreibt 1. Anliegen des Programms; 2. Steuerungsmaßnahmen des Programmträgers; 3. Innovationsbeiträge der Modellversuche und liefert 4. eine Zusammenfassende Einschätzung. (DIPF/DBS

Guidance in Model-based Compilations

The modeler should not be burdened with maintaining an overview over all potential conflicts. They should further be able to understand what is happening. Model-based compilers and modeling tools in general should guide a modeler.The KIELER Compiler constructs transformation snapshots and augmented models automatically during compilation. We demonstrate six different transient views that can help the modeler to refine their models and to solve modeling issues, such as causality problems in synchronous languages

Watch Your Compiler Work Compiler Models and Environments

We can observe many similarities between classical programming paradigms and model-driven engineering. A chain of model-to-model transformations often prescribes a particular work process, while executing such a chain generates a concrete instance of this process. Modeling the entire development process itself on a meta-model level extends the possibilities of the model-based approach to guide the developer. Besides refining tools for model creation, this kind of meta-modeling also facilitates debugging, optimization, and prototyping of new compilations. A compiler is such a process system. In this paper, we share the experiences gathered while we worked on the model-based reference compiler of the KIELER SCCharts project and ideas towards a unified view on similar prescribed processes. We exemplify our approach in two case studies

Pathways of intergenerational transmission of advantages during adolescence:Social background, cognitive ability, and educational attainment

Schulz W, Schunck R, Diewald M, Johnson W. Pathways of Intergenerational Transmission of Advantages during Adolescence: Social Background, Cognitive Ability, and Educational Attainment. Journal of Youth and Adolescence. 2017;46(10):2194-2214.Educational attainment in adolescence is of paramount importance for attaining higher education and for shaping subsequent life chances. Sociological accounts focus on the role of differences in socioeconomic resources in intergenerational reproduction of educational inequalities. These often disregard the intergenerational transmission of cognitive ability and the importance of children's cognitive ability to educational attainment. Psychological perspectives stress the importance of cognitive ability for educational attainment but underemphasize potentially different roles of specific socioeconomic resources in shaping educational outcomes, as well as individual differences in cognitive ability. By integrating two strands of research, a clearer picture of the pathways linking the family of origin, cognitive ability, and early educational outcomes can be reached. Using the population-based TwinLife study in Germany, we investigated multidimensional pathways linking parental socioeconomic position to their children's cognitive ability and academic track attendance in the secondary school. The sample included twins (N = 4008), respectively ages 11 and 17, and siblings (N = 801). We observed strong genetic influences on cognitive ability, whereas shared environmental influences were much more important for academic tracking. In multilevel analyses, separate dimensions of socioeconomic resources influenced child cognitive ability, controlling parental cognitive ability. Controlling adolescent cognitive ability and parental cognitive ability, parental socioeconomic resources also directly affected track attendance. This indicated that it is crucial to investigate the intertwined influences on educational outcomes in adolescence of both cognitive ability and the characteristics of the family of origin

Practical causality handling for synchronous languages

The synchronous principle is a well-established paradigm for reconciling concurrency with determinism. A key is to establish at compile time that a program or model is causal, which basically means that there exists a schedule that obeys the rules put down by the language. This rules out surprises at run time; however, in practice it can be rather cumbersome for the developer to cure causality problems, in particular as programs/models get more complex. We here propose to tackle this issue in two ways. Firstly, we propose to enrich the scheduling regime allowed by the language to not only consider data dependencies, but also explicit scheduling directives that operate on statements or coarser scheduling units. These directives may be used by the developer, or also by model-to-model transformations within the compiler. Secondly, we propose to enhance programming/modeling environments to guide the developer in finding causality issues. Specifically, we propose dedicated causality views that highlight data dependencies involved in scheduling conflicts, and structure-based editing to efficiently add scheduling directives. We illustrate our proposals for the SCCharts language. An Eclipse-based implementation based on the KIELER framework is available as open source

A sequentially constructive circuit semantics for Esterel

Static Single Assignment (SSA) is an established concept that facilitates various program optimizations. However, it is typically restricted to sequential programming. We present an approach that extends SSA for concurrent, reactive programming, specifically for the synchronous language Esterel. This extended SSA transformation expands the class of programs that can be compiled by existing Esterel compilers without causality problems. It also offers a new, efficient solution for the well-studied signal reincarnation problem. Finally, our approach rules out speculation/backtracking, unlike the recently proposed sequentially constructive model of computation

Using SCCharts models in Simulink to model an electronic control unit

When constructing an electrical racing car, special attention needs to be directed to the development of its engine control unit. Functionality of the motor-torque calculation and the integration of advanced driver assistance systems are crucial for the speed handling and hence, the safety of the car. The Kieler Formula Student Team Raceyard, which since 2011 has been constructing electrical racing cars annually, so far designed and tested its controller model in the popular commercial modeling software MATLAB/Simulink. This work shows how a functionally equivalent system can be designed by utilizing the visual synchronous language SCCharts in the academic open-source project KIELER. A complete controller model is modeled in KIELER and validated to behave the same as the original controller both in Simulink directly as well as in the 3D simulation environment IPG Carmaker. Tests on the performance of both controllers show that while a slowdown can be observed when comparing the generated C Code, simulation time in IPG Carmaker only increases by a negligible factor. KIELER’s developing and testing capabilities for synchronous models can therefore be considered a valuable tool in the process of designing, tuning and documenting such a controller model

Soliton binding and low-lying singlets in frustrated odd-legged S=1/2 spin tubes

Motivated by the intriguing properties of the vanadium spin tube Na2V3O7, we show that an effective spin-chirality model similar to that of standard Heisenberg odd-legged S=1/2 spin tubes can be derived for frustrated inter-ring couplings, but with a spin-chirality coupling constant alpha that can be arbitrarily small. Using density matrix renormalization group and analytical arguments, we show that, while spontaneous dimerization is always present, solitons become bound into low-lying singlets as alpha is reduced. Experimental implications for strongly frustrated tubes are discussed.Comment: 4 pages, 4 figure