Analyzing Product Lifecycle Costs for a Better Understanding of Cost Drivers in Additive Manufacturing

The costs of additive manufactured parts often seem too high in comparison to those of traditionally manufactured parts, as the information about major cost drivers, especially for additive manufactured metal parts, is weak. Therefore, a lifecycle analysis of additive manufactured parts is needed to understand and rate the cost drivers that act as the largest contributors to unit costs, and to provide a focus for future cost reduction activities for the Additive Manufacturing (AM) technology. A better understanding of the cost structure will help to compare the AM costs with the opportunity costs of the classical manufacturing technologies and will make it easier to justify the use of AM manufactured parts. This paper will present work in progress and methodology based on a sample investigated with business process analysis / simulation and activity based costing. In addition, cost drivers associated with metal AM process will be rated.Mechanical Engineerin

Innovation in the tension of change and reuse

Abstract not available

Comparison of instruments for particle number size distribution measurements in air quality monitoring

Number size distributions of airborne particles are relevant to fields including ambient monitoring, pharmaceutical and automotive measurements. A number of commercially available instruments can be used to determine particle number size distributions including the Electrical Low Pressure Impactor (ELPI), Scanning Mobility Particle Sizer (SMPS), Fast Mobility Particle Sizer (FMPS) and the Aerodynamic Particle Sizer (APS). The comparability of the data provided by these instruments has not been fully tested for different kinds of aerosols. This study compared number size distributions of laboratory generated aerosols (TiO2, NaCl, fumed silica and soot) in a wind tunnel. Reasonable agreement was noted between the different instruments, though there were divergences. For example the ELPI was inconsistent at the upper and lower limits of its working size (at low concentrations). Instruments responded variably to different particle types, which has important implications for sampling heterogeneous particle mixtures such as those found in urban air. This study highlights the need for caution when comparing data obtained from different particle instruments, and demonstrates the requirement for further comparison studies in controlled settings using an assortment of particle types with the aim to standardise and harmonise particle sampling protocols.<br/

Determining the contribution of tyre, clutch, brake and wearing course abrasion to the PM10 emissions of roads

Im Hinblick auf die prozessbezogenen Beiträge nicht-motorischer Partikelemissionen durch Abriebs- und Aufwirbelung existieren derzeit lediglich Studien, die an stark belasteten Innerortsstraßen oder in Tunneln durchgeführt wurden. Für die Emissionen von Autobahnen konnten die so gewonnenen Ergebnisse daher nicht ohne Weiteres als repräsentativ für die wesentlich häufiger anzutreffende Situation frei angeströmter Autobahnabschnitte betrachtet werden. Um diese Wissenslücke zu schließen, wurden im vorliegenden Projekt an der Autobahn A61 für mehr als 1 Jahr Luv-Lee Messungen durchgeführt. Mittels der NOx-Tracer-Methode wurden die in Tabelle 16 des Berichtes wiedergegebenen partikelmassen-bezogenen Emissionsfaktoren (EFs) ermittelt. Die EFs für PM10 sind mit Ergebnissen anderer Studien aus Deutschland beziehungsweise der Schweiz gut vergleichbar, während sich für die PM1-10-Fraktion geringere EFs ergaben, als aktuell angenommen. Mittels der Positiv-Matrix-Faktorisierung konnten neben den motorischen Emissionen vier nicht-motorische Quellfaktoren identifiziert und quantifiziert werden. Dabei zeigte sich neben einem deutlichen Einfluss durch Tausalzausbringung insbesondere die Relevanz von Bremsabrieb Diese Ergebnisse bestätigen somit auch für freiliegende Autobahnabschnitte die Signifikanz der nicht-motorischen Partikelemissionen für die PM10-Emissionen.Currently, only studies conducted at highly polluted streets within built-up areas or in tunnels exist concerning non-exhaust emissions from traffic caused by abrasion and resuspension. Results from these studies are therefore not directly transferable to emissions from highway traffic with free airflow. In order to close this gap of knowledge, upwind/downwind measurements at the German highway A61 were conducted for more than 1 year. Particle mass related emissions factors (EFs) (see table 16 of the report) were derived using the NOx tracer method. EFs for PM10 compare well with results from other studies from Germany and Switzerland, whereas the coarse fraction's EFs (PM1-10) are lower than those actually used in Germany. Using positive matrix factorisation (PMF) four non-exhaust sources could be identified and quantified. The relevance of brake abrasion was shown, together with a considerable influence due to road salting. These results confirm the importance of non-exhaust particle emissions regarding PM10 emissions also for highways in non-built-up areas with free air flow conditions

Performance Evaluation of Workflows Using Continuous Petri Nets with Interval Firing Speeds

In this paper, we study performance evaluation of workflow-based information systems. Because of state space explosion, analysis by stochastic models, such as stochastic Petri nets and queuing models, is not suitable for workflow systems in which a large number of flow instances run concurrently. We use fluid-flow approximation technique to overcome this difficulty. In the proposed method, GSPN (Generalized Stochastic Petri Nets) models representing workflows are approximated by a class of timed continuous Petri nets, called routing timed continuous Petri nets (RTCPN). In RTCPN models, each discrete set is approximated by a continuous region on a real-valued vector space, and variance in probability distribution is replaced with a real-valued interval. Next we derive piecewise linear systems from RTCPN models, and use interval methods to compute guaranteed enclosures for state variables. As a case study, we solve an optimal resource assignment problem for a paper review process