Universität Stuttgart
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Item Open Access Issues in designing object management systems(1990) Clow, Geoff; Plödereder, ErhardThis paper summarizes the discussions of the Object Management System (OMS) session at the Chinon Workshop. The session identified numerous capabilities which might be required in an OMS. The facilities which were agreed upon as essential to an OMS are presented in Section 1, OMS Core Facilities. A number of issues in the realization of these and other capabilities, influenced in part by specific application scenarios, are discussed in Section 2, OMS Requirements Issues. Promising applications requiring further investigation can be found in Section 3, Perceptions for the Future. Some global observations on the past and future conduct of the OMS field are summarized in Section 4, Concluding Observations.Item Open Access Computer simulation of anchoring technique in reinforced concrete beams(1990) Cervenka, Vladimir; Pukl, Radomir; Eligehausen, RolfThe load transfer in reinforced concrete structures by means of anchoring elements is very common in modern concrete technology. Anchoring elements are often inserted in the bottom surface of a structure and the load is transfered by tensile action of the concrete. In case of shear failure, the anchores are located in the most exposed tensile zone of beams. The shear failure can be thus influenced by anchoring elements. This effect was analysed by means of the finite element program SBETA, which is based on the nonlinear-elastic constitutive model. The comparison with experiments for several loading configurations was made. In the second part a computer simulation of similar experiments was conducted.Item Open Access Computer simulation: splitting tests of concrete thick-walled rings(1992) Pukl, Radomir; Schlottke, Bernd; Ozbolt, Josko; Eligehausen, RolfTwo non-linear program systems are used for a computer simulation of splitting failure of thick-walled concrete rings under internal radial pressure. Results of the numerical analyses for plane stress models, axisymmetrical model and 3D model are compared with available experimental data and empirical formulas. It is shown, that the behavior observed in experiments can be simulated, using advanced material models, namely the non local microplane model and SBETA material model based on the crack hand theory. With increasing outer radius of the ring, a size effect can be observed.Item Open Access SQL/XNF - processing composite objects as abstractions over relational data(1993) Mitschang, Bernhard; Pirahesh, Hamid; Pistor, Peter; Lindsay, Bruce; Südkamp, NorbertAn extension to SQL, called the SQL extended normal form (XNF), is discussed. It enhances relational technology by a composite object facility, which comprises not only extraction of composite objects from existing databases but also efficient navigation and manipulation facilities provided by an appropriate application programming interface. The language itself allows sharing of the database among normal form SQL applications and composite object applications. It provides proper subsetting of the database and subsequent structuring, exploiting subobject sharing and recursion, all based on its powerful composite object constructor concept, which is closed under the language operations. XNF is integrated into the relational framework, thus benefiting from the available technology such as relational engine and query optimization.Item Open Access Extraordinary biological membrane structures resulting from different local membrane curvatures(1992) Meyer, Helmut W.; Hülser, Dieter F.The bilayer arrangement of amphiphilic molecules is not only the basic structure of rather flat biological membranes, but also of regularly curved bilayers in most cubic phase structures. The basis of these cubic phase structures are infinite periodical minimal surfaces (IPMS). Extraordinary biological membrane structures resembling such IPMS were found as periodically curved bilayers in areas of the plasma membrane in a Streptomyces strain and in liposomes prepared from its extracted lipids. This structure consists of a transition of convex to concave curvatures and vice versa. A structure with curvatures in one direction only was observed in vacuolar membranes of yeast cells with a genetic defect. Our electron microscopical analysis of freeze fractured membranes of these cells revealed not only fully invaginated but also flat particle-free areas which were mainly circularly shaped, some elongated areas, however, were also present. In addition, sometimes periodical arrangements were detected which obviously are not related to IPMS structures. Both structures, however, indicate a high proportion of wedge-shaped lipid molecules in the bilayer.Item Open Access Quantification of aortic stenosis based on the morphology of Doppler ultrasound signals using image processing techniques(1994) Zahn, Thomas P.; Nagel, Joachim H.; Agatston, Arthur S.A method was developed to evaluate the morphologic structure of continuous wave Doppler ultrasound signals in order to quantify aortic valve stenosis in the human heart. The systolic peaks of the Doppler signal were assigned digital images and the stability of shape information was tested for patients with low stroke volume and aortal fibrillation. The results indicate that the shape of the signal peaks remains stable despite variations in amplitude and duration. The shape information was then used to quantify the severity of aortic stenosis by optimally matching Doppler peak images to selected templates representing typical diagnostic patterns. The developed software is capable of automatic extraction of shape information from Doppler ultrasound signals in order to support the clinical decision about valve functioning and replacement.Item Open Access 10 Gbit/s monolithic integrated Msm-photodiode AlGaAs/GaAs-HEMT optoelectronic receiver(1991) Hurm, Volker; Rosenzweig, Josef; Ludwig, Manfred; Benz, Willi; Osorio, Ricardo; Berroth, Manfred; Hülsmann, Axel; Kaufel, Gudrun; Köhler, Klaus; Raynor, Brian; Schneider, Joachim-Item Open Access Erfassung und Modellierung komplexer Funktionsfehler in Mikroelektronik-Bauelementen(1992) Stern, Olaf; Wunderlich, Hans-JoachimEs wird ein Verfahren vorgestellt, das für die Grundzellen einer Zellbibliothek layoutabhängig die möglichen Fehlfunktionen bestimmt, die durch Fertigungsfehler verursacht werden können. Eingabe für das Verfahren sind neben dem Layout einer Zelle die Prozeßparameter und die Defektverteilungen, Ausgabe sind die realistischen Fehlfunktionen mit ihren Auftrittswahrscheinlichkeiten. Damit können Testerzeugung und Testablauf beschleunigt, schwer testbare Fehler bestimmt und ihre Ursachen lokalisiert und beseitigt werden.Item Open Access Diagnosis and modelling of Alzheimer's disease through neural network analyses of PET studies(1990) Kippenhan, Jonathan Shane; Nagel, Joachim H.The back-propagation neural network algorithm was applied to the analysis of regional patterns in cerebral function, as demonstrated in positron emission tomography (PET). A trained network was able to successfully distinguish PET scans of normal subjects from PET scans of Alzheimer's Disease patients. It is concluded that the combination of PET and neural networks is a useful diagnostic tool for Alzheimer's Disease. A new paradigm for back-propagation learning is discussed which emphasizes its similarity to template matching. It is demonstrated that, under certain circumstances, the back-propagation network can be used as an estimation tool, as well as a classification tool, i.e., a trained neural network can indicate the criteria by which its classifications are performed.Item Open Access Size effect of the concrete cone failure load of anchor bolts(1992) Eligehausen, Rolf; Bouska, Petr; Cervenka, Vladimir; Pukl, RadomirThe concrete cone capacity of headed anchor bolts subjected to axial tension load was experimentally investigated using 35 concrete specimens of three different sizes. The dimensions of the test specimens were varied in proportion to the embedment depth h (h = 50, 150 and 450 mm). Material properties were measured on accompanying specimens. The measured failure loads are compared with other experimental and numerical investigations. According to the present results the failure loads increase in proportion to h 16, that means close to the prediction by linear fracture mechanics.