Serial-batch scheduling – the special case of laser-cutting machines

The dissertation deals with a problem in the field of short-term production planning, namely the scheduling of laser-cutting machines. The object of decision is the grouping of production orders (batching) and the sequencing of these order groups on one or more machines (scheduling). This problem is also known in the literature as "batch scheduling problem" and belongs to the class of combinatorial optimization problems due to the interdependencies between the batching and the scheduling decisions. The concepts and methods used are mainly from production planning, operations research and machine learning

Phenotypic Plasticity of Grass Root Anatomy in Response to Light Intensity and Nutrient Supply

The phenotypic plasticity of axial root anatomy was investigated in response to the availability of above- and below-ground resources using eight grass species of the genera Bromus and Poa. In a 7-week garden experiment nutrients were varied by a factor of five and light treatments of 100, 30 and 5·5% daylight were applied. Both nutrients and light influenced root structure. The effect of nutrients was largely explained by plant size, but this was not the case for light. Shading to 30% daylight led to a higher proportion of stele, larger stelar cells and larger xylem vessels. This can be understood either as an increased need for high transport capacity in the shade, where leaf area is larger but root mass lower than in full daylight, or as an increased resistance against desiccation, which is more of a hazard in open sites. Under 5·5% daylight, tissue mass density was reduced due to a lower proportion of stele, though xylem characteristics were not influenced when a correction for the effect of root cross-sectional area was applied. This response may be interpreted as a mechanism to maintain root function with a lower investment in biomass when growth is limited by low irradiance. The results show that the response of a plant to resource limitation is not restricted to those organs responsible for the acquisition of that resource. Furthermore, the qualitative response to shading depends on the absolute level of irradiance. For this reason, care is needed when comparing the results of shading experiments conducted under different irradiances. Copyright 2001 Annals of Botany Compan

Evidence for Orbital Order and its Relation to Superconductivity in FeSe0.4Te0.6

The emergence of nematic electronic states accompanied by a structural phase transition is a recurring theme in many correlated electron materials, including the high-temperature copper oxide- and iron-based superconductors. We provide evidence for nematic electronic states in the iron-chalcogenide superconductor FeSe0.4Te0.6 from quasi-particle scattering detected in spectroscopic maps. The symmetry-breaking states persist above Tc into the normal state. We interpret the scattering patterns by comparison with quasi-particle interference patterns obtained from a tight-binding model, accounting for orbital ordering. The relation to superconductivity and the influence on the coherence length are discussed.Comment: 5 pages, 5 figures, updated with published versio

Does Early Childhood Teacher Education Affect Students' Cognitive Orientations?

Early childhood teachers may differ regarding the knowledge base they use when making professional decisions. In this study two orientations are distinguished: the orientation towards scientific knowledge vs. the orientation towards intuition and subjective experience. As different tracks in early childhood teacher education qualify for professional practice, and as education of early childhood teachers matters with regard to developmental outcomes of children, knowledge orientations of prospective early childhood teachers attending universities and attending vocational schools are investigated and compared. Knowledge orientations were assessed by means of a questionnaire. After propensity score matching of 402 beginners and 402 graduates, multilevel analyses indicate that scientific orientation at the end of teacher education was higher and subjective orientation was lower than at the beginning. Furthermore, scientific knowledge orientation of BA-students was higher, subjective orientation was lower than of students at professional schools. Implications of these results regarding education of early childhood teachers are discussed

Discoloration of AISI 420 stainless steel in dependence of inter layer time during Laser-based Powder Bed Fusion

Parts built by laser-based powder bed fusion (PBF-LB) experience intervals of heating and cooling during the powder deposition and the selective melting of successive layers. Short time intervals of cooling can lead to heat accumulation resulting in discoloration of AISI 420 (X20Cr13) stainless steel parts. Discoloration occurs due to the formation of oxide layers, which negatively affect the corrosion resistance. This process is determined by the time-dependent influence of temperature and oxygen. Therefore, this study investigates effects of varied inter layer time on mechanical PBF-LB part properties and surface characteristics to prevent discoloration. EDX is used to analyze the chemical composition with regard to the chromium content as an indicator of reduced corrosion resistance. The results emphasize the need for implementing an minimum inter layer time greater than 12 s to prevent discoloration during the PBF-LB process with a layer thickness of 20 µm and a volume energy density of 113.3 J/mm

Which language-internal factors affect students’ capitalization performance in German?

Die satzinterne Großschreibung im Deutschen stellt für viele Schreiber*innen eine große Herausforderung dar. Während schon seit geraumer Zeit der traditionell wortartbezogene Ansatz als Ursache für diese Rechtschreibprobleme diskutiert wird, standen sprachstrukturelle Faktoren, die die Großschreibleistung beeinflussen, bisher wenig im Fokus. In der hier vorgestellten Studie wird die Bedeutung syntaktischer und morphologischer Merkmale von Abstrakta für die Großschreibung systematisch untersucht. Dazu wurden 1024 Testsätze konstruiert, bei denen die morphologische Struktur der Testwörter systematisch variiert und deren syntaktischen Kontexte systematisch kombiniert wurden. Die Testsätze wurden auf acht vergleichbare Testversionen mit jeweils 128 Testsätzen verteilt und 168 Siebtklässler*innen vorgelegt. Die Ergebnisse der Varianzanalysen zeigen, dass sowohl syntaktische als auch morphologische Merkmale die Großschreibleistung beeinflussen: Die Nominalgruppenstruktur, das Vorhandensein nominaler Suffixe sowie die Pluralfähigkeit der Abstrakta haben einen Einfluss auf die Großschreibleistung von Schüler*innen im 7. Schuljahr.In German, sentence-internal capitalization presents a major challenge to writers. Whereas the traditional lexical teaching approach has been under discussion as a potential cause for these orthographic difficulties, the impact of language-internal factors on writers’ performance has received little attention. The present study systematically investigates how syntactic and morphological characteristics of abstract nouns impact capitalization. To achieve this, 1,024 test sentences were constructed, incorporating test words whose morphological structure and syntactic contexts were systematically varied and combined. The test sentences were divided into eight comparable test versions, each containing 128 test sentences, and presented to 168 7th-grade students. The results of the variance analyses reveal that both syntactic and morphological characteristics influence capitalization: the structure of the noun phrase, the presence of nominal suffixes as well the ability of abstract nouns to form plurals affect 7th-grade students’ capitalization performance

Design of additively manufacturable injection molds with conformal cooling

Additive manufacturing enables the production of intricate geometries including internal structures. This design freedom can be used advantageously to enhance heat transfer in injection molds by means of conformal cooling. The main goal is to reduce cycle times and to improve part quality through uniform cooling of the plastic products. This paper presents cooling design concepts for mold inserts. Their underlying approaches differ with respect to the shape and the cross-sectional geometries of cooling channels. Distinct inserts are additively manufactured by laser-based powder bed fusion (PBF-LB) of AISI 420 stainless steel. Experiments are carried out on a custom thermal test bench. Infrared thermography is used to examine the surface temperature, showing a reduction in cooling time by up to 41 % compared to conventional concepts. Additionally, the coolant flow is measured. The evaluation of the cooling characteristics reveal a critical trade-off between cycle time and uniformity of the surface temperature

TIEMPO: an authoring and presentation system for interactive multimedia

The composition of interactive multimedia titles is a challenge for all advanced multimedia authoring tools. When non-interactive titles were specified by aligning the media items on a temporal axis such as time lines or tracks, now interactive multimedia titles require a non-linear temporal model. Thus, authoring becomes more complex, and the structure of a title is more difficult to visualize. TIEMPO addresses two areas: First, a temporal model satisfying the specification needs of interactive multimedia; Secondly, an interface for easy and rapid authoring of multimedia titles. This paper presents the architecture and design principles of the TIEMPO authoring and presentation environment