Browsing by Type "Buchbeitrag"

In the past various experimental investigations about room airflows were published. But most investiagtions are limited regarding measurements positions (restricted gflow patttern) and the availability of turbulent quantities (Reynolds-Stresses, entrainment, macroscopic instabilities etc.) based on the avaiable experimental data a targeted improvement of turbulence models is difficult. Therefore a complex three dimensional room airflow situation was investigatedwith three-dimensional Particle Image Velocmetry. Detailed informatiom of the floww, the Reynolds-stress distribution and the entertainment are presented. Based on the experimental results the behaviour of RANS-based turbulence models in predicting roomairflow is discussed. In this context, it is shown that intensive anisotropic Reynolds stresses near the wall arise and influences the airflow pattern. For this reason a new algebraic Reynolds stress turbulence model - which can in princible reproduce the turbulence anisotropic behaviour- is proposed. Compared with the linear eddy viscoity turbulence models the new nonlinear model agrees clearly better with the presented experimental findings.

Ultrasonically bonded Al wire bonds on Al metallization pads are widely used in power semiconductors. The required long time reliability of the devices is highly dependent on the interfacial quality of Al wire and the bond pad. Reliability of wire bonds is commonly assessed by thermal and power cycling tests. Accelerated mechanical fatigue testing can be used as an alternative to these time consuming procedures. In the present study, lifetime of thick Al wedge bonds on Si substrates was investigated using a novel mechanical fatigue testing technique operating at high frequencies and elevated temperatures. The influence of microstructure, testing temperature and frequency on lifetime of Al wire bonds was investigated. Finite element analysis was applied to calculate the stress distribution at the interfacial region and to establish life time prediction curves. The results of mechanical isothermal fatigue curves were compared and correlated with thermal cycling data of Al wire bonds. © 2014 The Minerals, Metals & Materials Society.

Die EU 2020 Ziele zur Senkung des Primärenergieverbrauchs bzw. Steigerung der Energieeffizienz fordern auch die moderne Gebäudetechnik zum aktiven handeln auf. Dafür braucht es eine ganzheitliche Betrachtung aller Systeme und Anlagen im Gebäude. Es reicht nicht aus nur einzelne Teilsysteme, wie beispielsweise Wärmebereitstellung oder Wärmeabgabesystem, bilanziell zu bewerten. Die Senkung des Primärenergieverbrauchs durch Steigerung der Energieeffizienz setzt eine genaue Kenntnis der Energiestromverteilung in den hydraulischen Verteilnetzen voraus. In dieser Arbeit rückt die non-invasive Temperaturmessung in den Mittelpunkt. Anhand eines vereinfachten Widerstandsmodells wird ein Korrekturalgorithmus entwickelt, der imstande ist, die Messabweichung zwischen invasiven und non-invasiven Temperatursensoren zu korrigieren. Bei dieser Methodik reicht die messtechnische Erfassung von Rohroberflächentemperatur und Umgebungstemperatur aus, um die annähernd wahre Temperatur des im Rohr strömenden Mediums zu ermitteln. Der Einsatz einer thermischen Isolierung rund um die non-invasive Messstelle wird ebenfalls thematisiert.

At a time when food procurement, food shortage, the stagnation in available arable land and rising population numbers are rising at an alarming rate, the importance of indoor farming is increasing. Indoor farming is an approach that allows fruits and vegetables to grow food in halls in racks, which gave birth to the term vertical farming. Vertical agriculture allows the optimization of food production by setting up adapted parameters in such a hall, thereby manipulating and boosting plant growth. However, since the necessary conditions for the growth can only be perfectly regulated for one type of plant per hall, it was considered to reduce the size of this unit and to design a box that provides the same functionality. In this paper I present a first prototype, which was designed as a Cyber Physical System (CPS), including power measurements of the included components. Furthermore, it demonstrates an economic approach for establishing this box in the Austrian economy based on a use case, followed by the advantages and disadvantages this change would entail. Finally, a calculation of expected costs in the first five years is presented.

An der Fachhochschule Burgenland werden die Bibliothekssoftwareprodukte Alephino von ExLibris, CONTENTdm von OCLC und Summon von Proquest eingesetzt. Im Artikel wird dargestellt, wie diese in einer Suchoberfläche zusammengeführt werden können. Abschließend wird die in diese Lösung integrierte Patron Driven Acquistion vorgestellt.