Cost Efficient Design and Planning for Additive Manufacturing Technologies

This paper discusses additive manufacturing with regards to the current available PDP's while setting a focus on the economic aspects of the integration.Mechanical Engineerin

One-electron bands, quantum Monte Carlo, and real superconductors

We use the doped Fullerenes as an example of how realistic systems can be described by simple models. Starting from the band structure we set up a tight-binding model that describes the t_{1u} conduction band. Adding correlation terms we arrive at a generalized Hubbard Hamiltonian that we treat using quantum Monte Carlo. To address the problem of superconductivity in the doped Fullerenes, we study the screening of a point charge. We find surprisingly efficient metallic screening even for strong correlations, almost up to the Mott transition, and discuss the implications on superconductivity, in particular the effect of the efficient screening on the Coulomb pseudopotential and the electron-phonon coupling.Comment: 9 pages LaTeX with 2 eps figures; Proceedings of the International Conference on Statistical Mechanics and Strongly Correlated Electrons in honor of Giovanni Paladin, Sept 27-29, 1999, Universita di Roma "La Sapienza"; additional material available at http://www.mpi-stuttgart.mpg.de/docs/ANDERSEN/fullerene

Reacting Flow Prediction of the Low-Swirl Lifted Flame in an Aeronautical Combustor With Angular Air Supply

The development of lean-burn combustion systems is of paramount importance for reducing the pollutant emissions of future aero engine generations. By tilting the burners of an annular combustor in circumferential direction relative to the rotational axis of the engine, the potential of increased combustion stability is opened up due to an enhanced exhaust gas recirculation between adjacent flames. The innovative gas turbine combustor concept, called the Short Helical Combustor (SHC), allows the main reaction zone to be operated at low equivalence ratios. To exploit the higher stability of the fuel-lean combustion, a low-swirl lifted flame is implemented in the staggered SHC burner arrangement. The objective is to reach ultra-low NOx emissions by complete evaporation and extensive premixing of fuel and air upstream of the lean reaction zone. In the present work, a modeling approach is developed to investigate the characteristics of the lifted flame in an enclosed single-burner configuration, using the gaseous fuel methane. It is demonstrated that by using the Large Eddy Simulation method, the shape and lift-off height of the flame is adequately reproduced by means of the finite-rate chemistry approach. For the numerical prediction of the lean lifted flame in the SHC arrangement, the focus is on the interaction of adjacent burners. It is shown that the swirling jet flow is deflected towards the sidewall of the staggered combustor dome, which is attributed to the asymmetrical confinement. Since the stabilization mechanism of the low-swirl flame relies on outer recirculation zones, the upstream transport of hot combustion products back to the flame base is studied by the variation of the combustor confinement ratio. It turns out that increasing the combustor size amplifies the exhaust gas recirculation along the sidewall, and increases the temperature of recirculating burned gases. The present study emphasizes the capability of the proposed lean-burn combustor concept for future aero engine applications

Reacting Flow Prediction of the Low-Swirl Lifted Flame in an Aeronautical Combustor With Angular Air Supply

The development of lean-burn combustion systems is of paramount importance for reducing the pollutant emissions of future aero engine generations. By tilting the burners of an annular combustor in circumferential direction relative to the rotational axis of the engine, the potential of increased combustion stability is opened up due to an enhanced exhaust gas recirculation between adjacent flames. The innovative gas turbine combustor concept, called the short helical combustor (SHC), allows the main reaction zone to be operated at low equivalence ratios. To exploit the higher stability of the fuel-lean combustion, a low-swirl lifted flame is implemented in the staggered SHC burner arrangement. The objective is to reach ultralow NOx emissions by complete evaporation and extensive premixing of fuel and air upstream of the lean reaction zone. In this work, a modeling approach is developed to investigate the characteristics of the lifted flame in an enclosed single-burner configuration, using the gaseous fuel methane. It is demonstrated that by using the large eddy simulation method, the shape and liftoff height of the flame are adequately reproduced by means of the finite-rate chemistry approach. For the numerical prediction of the lean lifted flame in the SHC arrangement, the focus is on the interaction of adjacent burners. It is shown that the swirling jet flow is deflected toward the sidewall of the staggered combustor dome, which is attributed to the asymmetrical confinement. Since the stabilization mechanism of the low-swirl flame relies on outer recirculation zones, the upstream transport of hot combustion products back to the flame base is studied by the variation of the combustor confinement ratio. It turns out that increasing the combustor size amplifies the exhaust gas recirculation along the sidewall, and increases the temperature of recirculating burned gases. This study emphasizes the capability of the proposed lean-burn combustor concept for future aero engine applications

Which factors influence the psychological distress among relatives of patients with chronic functional psychoses? An exploratory study in a community mental health care setting

Aim: This research aimed to assess the contribution of the five core areas of the transactional stress model to the relatives' psychological distress (PD) when informally taking care of patients with functional psychoses treated in community mental health care. Subjects and methods: Cross-sectional data from 163 relatives were collected in interviews, while data on 158 patients were collected by analyzing clinical charts. The following areas were assessed: socio-demographic and illness-related features of the patients, socio-demographic features of the relatives (environmental variables); sense of coherence, mastery, causal attributions and opinions of relatives about mental disorders (person variables); interpersonal problems with the patients as well as the assessment of their symptoms by the relatives themselves (primary appraisal); support received, critical life events and burden of relatives caused by their own illnesses (secondary appraisal); control behavior and efforts of relatives to engage the patients in activities (coping). PD was assessed with the 12-item version of the General Health Questionnaire. Bi-variate correlation analysis and a multiple linear regression model were the main test statistical approaches. Results: Correlation analysis showed that differences between diagnostic groups referred to primary and secondary appraisal processes, in particular. Results of the statistical model provided evidence for the importance of primary appraisal and person variables for influencing PD, and for the lack of importance of coping and environmental variables. Conclusion: The study enhanced the validity of the transactional stress model to demonstrate the influence of salutogenetic concepts such as sense of coherence

MorphoCluster: Efficient Annotation of Plankton Images by Clustering

In this work, we present MorphoCluster, a software tool for data-driven, fast, and accurate annotation of large image data sets. While already having surpassed the annotation rate of human experts, volume and complexity of marine data will continue to increase in the coming years. Still, this data requires interpretation. MorphoCluster augments the human ability to discover patterns and perform object classification in large amounts of data by embedding unsupervised clustering in an interactive process. By aggregating similar images into clusters, our novel approach to image annotation increases consistency, multiplies the throughput of an annotator, and allows experts to adapt the granularity of their sorting scheme to the structure in the data. By sorting a set of 1.2 M objects into 280 data-driven classes in 71 h (16 k objects per hour), with 90% of these classes having a precision of 0.889 or higher. This shows that MorphoCluster is at the same time fast, accurate, and consistent; provides a fine-grained and data-driven classification; and enables novelty detection

Numerical Investigation of the Low-Swirl Flow in an Aeronautical Combustor With Angular Air Supply

Civil air traffic is predicted to further grow in the near future. Hence, the development of aeronautical combustors will face major challenges to meet future stringent environmental regulations. In the present study, an innovative gas turbine combustor with angular air supply called Short Helical Combustor (SHC) is investigated. The main feature of this concept is the helical arrangement of the fuel injectors around the turbine shaft. Aiming at the implementation of a lean-burn concept, a low-swirl lifted flame is adopted. This flame is lifted off and not anchored to the injector which opens the potential of low NOx emissions due to a high degree of premixing within the combustor. In this work, isothermal flow characteristics of such a generic SHC combustor are studied by use of RANS predictions with special emphasis on the interaction of adjacent low-swirl flows. For evaluating the influence of injector parameters on the flow field, a parametric study based on single sector simulations is performed. It is shown that the asymmetrically confined swirling jet flow is strongly deflected towards the sidewall of the staggered SHC dome. The deflection of the flow is associated with an asymmetric pressure field in the vicinity of the burner which is generally known as Coandă effect. As a consequence of the deflected flow, the angular momentum flux at combustor outlet is increased. The interaction of the low-swirl jet and the SHC sidewall is investigated with regards to backflow momentum and residence time in the recirculation zone. It is concluded that by modifying the momentum of the air flow through the injector, the amount of recirculating air flowing back along combustor walls is strongly affected. The present work establishes an understanding of the underlying aerodynamics of the SHC concept which is essential for matching the requirements of lean lifted flames

Microscopic Imaging Spray Diagnostics under High Temperature Conditions: Application to Urea–Water Sprays

The quantitative investigation of droplet laden turbulent flows at high temperature conditions is of great importance for numerous applications. In this study, an experiment was set up for investigation of evaporating urea-water sprays, which are relevant for the effective reduction of nitrogen oxide emissions of diesel engines using Selective Catalytic Reduction. A shadowgraphy setup is pushed to its limits in order to detect droplet diameters as small as 4µm and droplet velocities up to 250m/s. In addition, the operating conditions of the gaseous flow of up to 873K and 0.6MPa are an additional challenge. Due to the high temperature environment, image quality is prone to be compromised by schlieren effects and astigmatism phenomena. A water-cooled window and an astigmatism correction device are installed in order to correct these problems. The results to be presented include characteristics of the turbulent gas flow as well as detailed spray characteristics at different positions downstream of the atomizer. It is demonstrated that the velocity of the gas can be approximated by the velocity of the smallest detectable droplets with sufficient accuracy. Furthermore, the statistical analysis of velocity fluctuations provides data for predicting the turbulent dispersion of the droplets

Qualitätsbegriffe, Risikobewertung und Risikomanagement in Pharmazie und Biotechnologie:Beitrag zur Politökonomischen Kritik des Gesundheitswesens

QM-Systeme, Risikobewertung, Risikomanagement und soziale Genese von Qualität werden auf der Basis marxistischer Theorie untersucht. Ansatzweise werden Risikomanagement, Verfahren der Aussagenlogik und der Evidenz-basierten Medizin (Rolle der Krankenversicherung, Disease Management Programme) auf ihre Funktion als Herrschaftsmatrix hinterfragt. Der Qualitätsbegriff (Beschaffenheitskriterium) im Konzept der substanziellen Äquivalenz verschleiert Problemstellen (pleiotrope Effekte). Diese Effekte sind seit den 60er Jahren bekannt, aber in der Literatur nicht beschrieben. Mit der Biotechnologie kam die Chance, Qualitätsbrüche und Diskontinuitäten in der Produktentwicklung systematisch zu erarbeiten. Vermutet wird, daß Methoden und Qualitätsbegriffe der Pharmazie/Pharmakologie trotz ihrer Defizite wegen ihrer sozialen Akzeptanz von der Biotechnologie unverändert übernommen werden