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The ClearPET™ project is proposed by working groups of the Crystal Clear Collaboration (CCC) to develop a 2nd generation high performance small animal positron emission tomograph (PET). High sensitivity and high spatial resolution is foreseen for the ClearPET™ camera by using a phoswich arrangement combining mixed lutetium yttrium aluminum perovskite (LuYAP:Ce) and lutetium oxyorthosilicate (LSO) scintillating crystals. Design optimizations for the first photomultiplier tube (PMT) based ClearPET camera are done with a Monte-Carlo simulation package implemented on GEANT3 (CERN, Geneva, Switzerland). A dual-head prototype has been built to test the frontend electronics and was used to validate the implementation of the GEANT3 simulation tool. Multiple simulations were performed following the experimental protocols to measure the intrinsic resolution and the sensitivity profile in axial and radial direction. Including a mean energy resolution of about 27.0% the simulated intrinsic resolution is about (1.41±0.11)mm compared to the measured of (1.48±0.06)mm. The simulated sensitivity profiles show a mean square deviation of 12.6% in axial direction and 3.6% in radial direction. Satisfactorily these results are representative for all designs and confirm the scanner geometry.
IASSE-2004 - 13th International Conference on Intelligent and Adaptive Systems and Software Engineering eds. W. Dosch, N. Debnath, pp. 245-250, ISCA, Cary, NC, 1-3 July 2004, Nice, France We introduce a UML-based model for conceptual design support in civil engineering. Therefore, we identify required extensions to standard UML. Class diagrams are used for elaborating building typespecific knowledge: Object diagrams, implicitly contained in the architect’s sketch, are validated against the defined knowledge. To enable the use of industrial, domain-specific tools, we provide an integrated conceptual design extension. The developed tool support is based on graph rewriting. With our approach architects are enabled to deal with semantic objects during early design phase, assisted by incremental consistency checks.
A 2nd generation high performance small animal PET scanner, called ClearPET™, has been designed and a first prototype is built by working groups of the Crystal Clear Collaboration (CCC). In order to achieve high sensitivity and maintain good uniform spatial resolution over the field of view in high resolution PET systems, it is necessary to extract the depth of interaction (DOI) information and correct for spatial degradation. The design of the first ClearPET™ Demonstrator based on the use of the multi-anode photomultiplier tube (Hamamatsu R7600-M64) and a LSO/LuYAP phoswich matrix. The two crystal layers of 8*8 crystals (2*2*10 mm3) are stacked on each other and mounted without light guide as one to one on the PMT. A unit of four PMTs arranged in-line represents one of 20 sectors of the ring design. The opening diameter of the crystal ring is 137 mm, the axial detector length is 110 mm. The PMT pulses are digitized by free-running ADCs and digital data processing determines the gamma energy, the phoswich layer and even the pulse arrival time. Single gamma interactions are recorded and coincidences are found by software. The gantry allows rotation of the detector modules around the field of view. The measurements have been done using the first LSO/LuYAP detector cassettes.
The ClearPET project
(2004)
The Crystal Clear Collaboration has designed and is building a high-resolution small animal PET scanner. The design is based on the use of the Hamamatsu R7600-M64 multi-anode photomultiplier tube and a LSO/LuYAP phoswich matrix with one to one coupling between the crystals and the photo-detector. The complete system will have 80 PM tubes in four rings with an inner diameter of 137 mm and an axial field of view of 110 mm. The PM pulses are digitized by free-running ADCs and digital data processing determines the gamma energy, the phoswich layer and even the pulse arrival time. Single gamma interactions are recorded and coincidences are found by software. The gantry allows rotation of the detector modules around the field of view. Simulations, and measurements a 2×4 module test set-up predict a spatial resolution of 1.5 mm in the centre of the field of view and a sensitivity of 5.9% for a point source in the centre of the field of view.
Within the Crystal Clear Collaboration a modular system for a small animal PET scanner (ClearPET™) has been developed. The modularity allows the assembly of scanners of different sizes and characteristics in order to fit the specific needs of the individual member institutions. Now a first demonstrator is being completed in Julich. The system performs depth of interaction detection by using a phoswich arrangement combining LSO and LuYAP scintillators which are coupled to multi-channel photomultipliers (PMTs). A free-running ADC digitizes the signal from the PMT and the complete scintillation pulses are sampled by an FPGA and sent with 20 MB/S to a PC for preprocessing. The pulse provides information about the gamma energy and the scintillator material which identifies the interaction layer. Furthermore, the exact pulse starting time is obtained from the sampled data. This is important as no hardware coincidence detection is implemented. All single events are recorded and coincidences are identified by software. An advantage of that is that the coincidence window and the dimensions of the field of view can be adjusted easily. The ClearPET™ demonstrator is equipped with 10240 crystals on 80 PMTs. This paper presents an overview of the data acquisition system.
Improved collapse loads of thick-walled, crack containing pipes and vessels are suggested. Very deep cracks have a residual strength which is better modelled by a global limit load. In all burst tests, the ductility of pressure vessel steels was sufficiently high whereby the burst pressure could be predicted by limit analysis with no need to apply fracture mechanics. The relative prognosis error increases however, for long and deep defects due to uncertainties of geometry and strength data.
Applications of Graph Transformations with Industrial Relevance Lecture Notes in Computer Science, 2004, Volume 3062/2004, 90-105, DOI: 10.1007/978-3-540-25959-6_7 In this paper we discuss how tools for conceptual design in civil engineering can be developed using graph transformation specifications. These tools consist of three parts: (a) for elaborating specific conceptual knowledge (knowledge engineer), (b) for working out conceptual design results (architect), and (c) automatic consistency analyses which guarantee that design results are consistent with the underlying specific conceptual knowledge. For the realization of such tools we use a machinery based on graph transformations. In a traditional PROGRES tool specification the conceptual knowledge for a class of buildings is hard-wired within the specification. This is not appropriate for the experimentation platform approach we present in this paper, as objects and relations for conceptual knowledge are due to many changes, implied by evaluation of their use and corresponding improvements. Therefore, we introduce a parametric specification method with the following characteristics: (1) The underlying specific knowledge for a class of buildings is not fixed. Instead, it is built up as a data base by using the knowledge tools. (2) The specification for the architect tools also does not incorporate specific conceptual knowledge. (3) An incremental checker guarantees whether a design result is consistent with the current state of the underlying conceptual knowledge (data base).
Miniaturisierte Referenzelektroden in Siliziumtechnologie für elektrochemische Sensoranwendungen
(2004)
This study has been performed to design the combination of the new ClearPET TM (ClearPET is a trademark of the Crystal Clear Collaboration), a small animal Positron Emission Tomography (PET) system, with a microComputed Tomography (microCT) scanner. The properties of different microCT systems have been determined by simulations based on GEANT4. We demonstrate the influence of the detector material and the X-ray spectrum on the obtained contrast. Four different detector materials (selenium, cadmium zinc telluride, cesium iodide and gadolinium oxysulfide) and two X-ray spectra (a molybdenum and a tungsten source) have been considered. The spectra have also been modified by aluminum filters of varying thickness. The contrast between different tissue types (water, air, brain, bone and fat) has been simulated by using a suitable phantom. The results indicate the possibility to improve the image contrast in microCT by an optimized combination of the X-ray source and detector material.
In: Net-distributed Co-operation : Xth International Conference on Computing in Civil and Building Engineering, Weimar, June 02 - 04, 2004 ; proceedings / [ed. by Karl Beuke ...] . - Weimar: Bauhaus-Univ. Weimar 2004. - 1. Aufl. . Seite 1-14 ISBN 3-86068-213-X International Conference on Computing in Civil and Building Engineering <10, 2004, Weimar> Summary In our project, we develop new tools for the conceptual design phase. During conceptual design, the coarse functionality and organization of a building is more important than a detailed worked out construction. We identify two roles, first the knowledge engineer who is responsible for knowledge definition and maintenance; second the architect who elaborates the conceptual de-sign. The tool for the knowledge engineer is based on graph technology, it is specified using PROGRES and the UPGRADE framework. The tools for the architect are integrated to the in-dustrial CAD tool ArchiCAD. Consistency between knowledge and conceptual design is en-sured by the constraint checker, another extension to ArchiCAD.
MultiChannel Photomultipliers (PM), like the R7600-00-M64 or R5900-00-M64 from Hamamatsu, are often chosen as photodetectors in high-resolution positron emission tomography (PET). A major problem of this PM is the nonuniform channel gain. In order to solve this problem, light attenuating masks were created. The aim of the masks is a homogenization of the output of all 64 channels using different hole sizes at the channel positions. The hole area, which is individually defined for the different channels, is inversely proportional to the channel gain. The measurements by inserting light attenuating masks improved a homogenization to a ratio of 1:1.2.
Der konstruktive Entwurf wird in derzeitigen CAD-Systemen gut unterstützt, nicht aber der konzeptuelle Gebäude-Entwurf. Dieser abstrahiert von konstruktiven Elementen wie Linie, Wand oder Decke, um auf die Konzepte, d.h. die eigentlichen Funktionen, heraus zu arbeiten. Diese abstraktere, funktionale Sichtweise auf ein Gebäude ist während der frühen Entwurfsphase essentiell, um Struktur und Organisation des gesamten Gebäudes zu erfassen. Bereits in dieser Phase muss Fachwissen (z. B. rechtliche, ökonomische und technische Bestimmungen) berücksichtigt werden. Im Rahmen des vorliegenden Projekts werden Software-Werkzeuge integriert in industrielle CAD-Systeme entwickelt, die den konzeptuellen Gebäude-Entwurf ermöglichen und diesen gegen Fachwissen prüfen. Das Projekt ist in zwei Teile gegliedert. Im Top-Down-Ansatz werden Datenstrukturen und Methoden zur Strukturierung, Repräsentation und Evaluation von gebäudespezifischem Fachwissen erarbeitet. Dieser Teil baut auf den graphbasierten Werkzeugen PROGRES und UPGRADE des Lehrstuhls auf. Der Bottom-Up-Ansatz ist industriell orientiert und hat zum Ziel, das kommerzielle CAD-System ArchiCAD zu erweitern. Hierbei soll der frühe, konzeptuelle Gebäude-Entwurf in einem CAD-System ermöglicht werden. Der Entwurf kann darüber hinaus gegen das definierte Fachwissen geprüft werden. Im Rahmen des graphbasierten Top-Down-Ansatzes wurde zunächst eine neue Spezifikationsmethode für die Sprache PROGRES entwickelt. Das PROGRES-System erlaubt die Spezifikation von Werkzeugen in deklarativer Form. Üblicherweise wird domänenspezifisches Fachwissen in der PROGRES-Spezifikation codiert, das daraus generierte visuelle Werkzeug stellt dann die entsprechende Funktionalität zur Verfügung. Mit dieser Methode sind am Lehrstuhl für Informatik III Werkzeuge für verschie-dene Anwendungsdomänen entstanden. In unserem Fall versetzen wir einen Domänen-Experten, z. B. einen erfahrenen Architekten, in die Lage, Fachwissen zur Laufzeit einzugeben, dieses zu evaluieren, abzuändern oder zu ergänzen. Im Rahmen der bisherigen Arbeit wurde dazu eine parametrisierte PROGRES-Spezifikation und zwei darauf aufbauende Werkzeuge entwickelt, welche die dynamische Eingabe von gebäude-technisch relevantem Fachwissen erlauben und einen graphbasierten, konzeptuellen Gebäude-Entwurf ermöglichen. In diesem konzeptuellen Gebäude-Entwurf wird von Raumgrößen und Positionen abstrahiert, um die funktionale Struktur eines Gebäudes zu beschreiben. Das Fachwissen kann von einem Architekten visuell definiert werden. Es können semantische Einheiten, im einfachsten Fall Räume, nach verschiedenen Kriterien kategorisiert und klassifiziert werden. Mit Hilfe von Attributen und Relationen können die semantischen Einheiten präziser beschrieben und in Beziehung zueinander gesetzt werden. Die in PROGRES spezifizierten Konsistenz-Analysen erlauben die Prüfung eines graphbasierten konzeptuellen Gebäude-Entwurfs gegen das dynamisch eingefügte Fachwissen. Im zweiten Teil des Forschungsprojekts, dem Bottom-Up-Ansatz, wird das CAD-System ArchiCAD erweitert, um den integrierten konzeptuellen Gebäude-Entwurf zu ermöglichen. Der Architekt erhält dazu neue Entwurfselemente, die Raumobjekte, welche die relevanten semantischen Einheiten während der frühen Entwurfsphase repräsentieren. Mit Hilfe der Raumobjekte kann der Architekt in ArchiCAD den Grundriss und das Raumprogramm eines Gebäudes entwerfen, ohne von konstruktiven Details in seiner Kreativität eingeschränkt zu werden. Die Arbeitsweise mit Raumobjekten entspricht dem informellen konzeptuellen Entwurf auf einer Papierskizze und ist daher für den Architekten intuitiv und einfach zu verwenden. Durch die Integration in ArchiCAD ergibt sich eine weitere Unterstützung: Das im Top-Down-Ansatz spezifizierte Fach-wissen wird verwendet, um den konzeptuellen Gebäude-Entwurf des Architekten auf Regelverletzungen zu überprüfen. Entwurfsfehler werden angezeigt. Zum Abschluss des konzeptuellen Gebäude-Entwurfs mit Raumobjekten wird durch ein weiteres neu entwickeltes Werkzeug eine initiale Wandstruktur automatisch erzeugt, die als Grundlage für die folgenden konstruktiven Entwurfsphasen dient. Alle beschriebenen Erwei-terungen sind in ArchiCAD integriert, sie sind für den Architekten daher leicht zu erlernen und einfach zu bedienen.
Mechanical stimulation of the cells resulted in evident changes in the cell morphology, protein composition and gene expression. Microscopically, additional formation of stress fibers accompanied by cell re-arrangements in a monolayer was observed. Also, significant activation of p53 gene was revealed as compared to control. Interestingly, the use of CellTech membrane coating induced cell death after mechanical stress had been applied. Such an effect was not detected when fibronectin had been used as an adhesion substrate.
Farbanalyse von gebackenen oder frittierten Nahrungsmitteln und Vorhersage des Acrylamid-Wertes
(2004)
Applications of Graph Transformations with Industrial Relevance Lecture Notes in Computer Science, 2004, Volume 3062/2004, 434-439, DOI: http://dx.doi.org/10.1007/978-3-540-25959-6_33 This paper gives a brief overview of the tools we have developed to support conceptual design in civil engineering. Based on the UPGRADE framework, two applications, one for the knowledge engineer and another for architects allow to store domain specific knowledge and to use this knowledge during conceptual design. Consistency analyses check the design against the defined knowledge and inform the architect if rules are violated.
This work is an attempt to answer the question: How to use convex programming in shakedown analysis of structures made of materials with temperature-dependent properties. Based on recently established shakedown theorems and formulations, a dual relationship between upper and lower bounds of the shakedown limit load is found, an algorithmfor shakedown analysis is proposed. While the original problem is neither convex nor concave, the algorithm presented here has the advantage of employing convex programming tools.
An optimization method is developed to describe the mechanical behaviour of the human cancellous bone. The method is based on a mixture theory. A careful observation of the behaviour of the bone material leads to the hypothesis that the bone density is controlled by the principal stress trajectories (Wolff’s law). The basic idea of the developed method is the coupling of a scalar value via an eigenvalue problem to the principal stress trajectories. On the one hand this theory will permit a prediction of the reaction of the biological bone structure after the implantation of a prosthesis, on the other hand it may be useful in engineering optimization problems. An analytical example shows its efficiency.