Technische Hochschule Würzburg-Schweinfurt Publikationsserver OPUS
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Stability Analysis of Converter-Dominated Power Systems by Phasor-Based and Electromagnetic Transient Simulation
No full textForce-free Angle Measurements
No full textModerne, digitale, automatisierte Tachymeter bieten einen flexiblen Einsatz und erfordern gleichzeitig flexible Rechenverfahren. Einschränkungen der tradierten Auswerteverfahren in Bezug auf die Richtungsmessungen in den Zenit und in Richtung der Nullrichtung (Nullpunkt des Teilkreises) sind dabei nicht akzeptabel. Daher wird in diesem Beitrag ein neuer, auf Richtungsvektoren basierender Umgang mit Richtungsmessungen vorgeschlagen. Der direkte Vergleich des tradierten Verfahrens mit dem neuen Ansatz zeigt das neu gewonnene Potential, letztlich aber auch die Notwendigkeit, das Geodätische Rechnen neu zu erfinden.Modern, digital, automated total stations offer flexible use and at the same time require flexible calculation methods. Limitations of the traditional evaluation methods with regard to the angle measurements into the zenith and in the zero direction (zero point of the horizontal circle) are not acceptable. Therefore, a new handling of direction measurements based on direction vectors is proposed in this paper. The direct comparison of the traditional method with the new approach shows the newly gained potential, but ultimately also the necessity to reinvent geodetic computing
"Egal, wie rausgeballert ich bin, die sind da" - Intensive Sozialpädagogische Einzelbetreuung als aufsuchende Soziale Arbeit
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Reentrant Flow Shop Production Control with the Theory of Constraints for Wafer Fabrication Having Parallel Machines
No full textPurpose of this paper:
In a production line with capacity constraint resources (CCR) or bottleneck stations, the
production control and the throughput rate are determined by the CCR station. In this
study, we consider a production system with parallel machines and there are many rounds
of reentrants during the production processes, and can be regarded as a reentrant flow
shop process (RFS). In most RFS systems, the release of jobs is a push type without
considering the WIP in each layer of reentrance. To resolve the excessive WIP in an RFS
system, we consider the theory of constraints (TOC) and implement the DBR (drum,
bottleneck and rope) to model RFS scheduling and to define appropriate buffer sizes at the
CCR stations of diverse reentrant layers.
Design/methodology/approach STS:
We obtain production data of a type of semiconductor chip where the photolithography
process is the most frequent reentrant. We designed nine scenarios based on the current
RFS of the case company by applying the TOC and considering the time differences in
parallel machines. A simulation model for the photolithography process was established
using AutoMod simulation. Thirty simulation runs were performed for the mean and
standard deviation. The goal is to identify the best scenario among the nine proposed ones.
Findings:
The simulation results demonstrated that Scenario 9, which involves dynamic buffers and
assigning higher priority to products with more processing reentrance layers, achieved the
highest throughput of finished products. The throughput of finished products in Scenario 9
is 22% higher than in the base scenario. It also shows improvements in maximum product
stack-up and input-output ratio compared to the base scenario.
Value:
The paper studies dispatching rules for reentrant flow lines having parallel machines with
data from the semiconductor industry, and this type of production system is common for
producing a wide range of electronic devices. With limited buffer sizes on the shop floor,
the number of WIPs is significant, especially for reentrant flow shops, to avoid being
clogged with too many WIPs. Implementing DBR modeling from TOC, the nine scenarios
demonstrate the effects of controlling buffer sizes on system performances.
Research limitations/implications:
The nine scenarios are designed based on the case company situations and may not be
readily implemented in other industries. Moreover, the DBR modeling of the buffer sizes
and CCR station schedule control should also be adjusted when employed in other
applications
M A K Halliday’s Systemic Functional Linguistics and the Hermeneutic Spiral: Interpreting Alajos Unger’s late Nazarene painting Baptism of Vajk (1842)
Get PDFMichael O’Toole’s functional semiotic model based on Hallidayan linguistics is applied to a hermeneutic analysis of 19th century art of the Austrian Empire. The obscure painter Alajos Unger (1814-1848) from Győr, Hungary, was the son of playing-card maker Mátyás Unger the Elder (1789–1862) and a designer of award-winning playing cards during Vormärz (the Reform Era in Hungary). He trained at the Vienna Art Academy, and two of his paintings (The recapture of Győr 1598, 1840; Family portrait, 1843) are in the collection of the Hungarian National Gallery. His Baptism of Vajk (1842) is the only such Nazarene history painting known in Hungarian art. Nazarene art, recently reappraised as modern, conceptual art, influenced the British Pre-Raphaelites and thus modern Hungarian art. Due to its symbolic nature, it is ideal for functional semiotic interpretation. Such an analysis of Unger’s Baptism of Vajk identifies its patriotic, yet conservative, Catholic pro-Habsburg stance promoting dynastic piety (Pietas Hungarica) and a supra-national, cosmopolitan stance opposed to nationalist rhetoric as part of a cycle of paintings created by the artist
Fatigue strength of repair-welded headed studs
Get PDFWelded connections of headed studs are highly stressed details in bridge structures in steel-concrete composite construction and are largely responsible for the functionality of the supporting structures. At the same time, this detail requires a lot of resources due to the high welding effort and therefore has a major influence on the economic success. An important criterion for the economic and ecological balance of the structure is the durability of the welded joint, which is quantified by the fatigue strength. The welding of headed studs for composite bridges is usually carried out using fully mechanised drawn arc stud welding in accordance with EN ISO 14555. Due to the process, stud welds that do not fulfil the standard requirements for flawless condition may occur in individual cases. The design rules for stud load-bearing capacity in accordance with EN 1994-2 are based on tests and only apply to connections produced using drawn arc stud welding. In the past, there were practicable and tacitly accepted solutions for repairing such sporadically occurring faulty welds, but these were never systematically investigated. Particularly against the background of fatigue loading, repair-welded stud connections are now to be systematically investigated in a project funded by the AIF. The article provides an overview of the execution of stud welded joints and presents the tests planned in the project in order to achieve a practicable recommendation for the repair welding of headed studs
Active thermography for in-situ defect detection in laser powder bed fusion of metal
Get PDFAdditive manufacturing (AM) has revolutionized production by offering design flexibility, reducing material waste, and enabling intricate geometries that are often unachievable with traditional methods. As the use of AM for metals continues to expand, it is crucial to ensure the quality and integrity of printed components. Defects can compromise the mechanical properties and performance of the final product. Non-destructive testing (NDT) techniques are necessary to detect and characterize anomalies during or post-manufacturing. Active thermography, a thermal imaging technique that uses an external energy source to induce temperature variations, has emerged as a promising tool in this field. This paper explores the potential of in-situ non-destructive testing using the processing laser of a PBF-LB/M setup as an excitation source for active thermography. With this technological approach, artificially generated internal defects underneath an intact surface can be detected down to a defect size of 350 μm – 450 μm