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Research collaborations provide opportunities for both practitioners and researchers: practitioners need solutions for difficult business challenges and researchers are looking for hard problems to solve and publish. Nevertheless, research collaborations carry the risk that practitioners focus on quick solutions too much and that researchers tackle theoretical problems, resulting in products which do not fulfill the project requirements.
In this paper we introduce an approach extending the ideas of agile and lean software development. It helps practitioners and researchers keep track of their common research collaboration goal: a scientifically enriched software product which fulfills the needs of the practitioner’s business model.
This approach gives first-class status to application-oriented metrics that measure progress and success of a research collaboration continuously. Those metrics are derived from the collaboration requirements and help to focus on a commonly defined goal.
An appropriate tool set evaluates and visualizes those metrics with minimal effort, and all participants will be pushed to focus on their tasks with appropriate effort. Thus project status, challenges and progress are transparent to all research collaboration members at any time.
This paper presents a two-dimensional-in-space mathematical model of biosensors based on an array of enzyme microreactors immobilised on a single electrode. The modeling system acts under amperometric conditions. The microreactors were modeled by particles and by strips. The model is based on the diffusion equations containing a nonlinear term related to the Michaelis-Menten kinetics of the enzymatic reaction. The model involves three regions: an array of enzyme microreactors where enzyme reaction as well as mass transport by diffusion takes place, a diffusion limiting region where only the diffusion takes place, and a convective region, where the analyte concentration is maintained constant. Using computer simulation, the influence of the geometry of the microreactors and of the diffusion region on the biosensor response was investigated. The digital simulation was carried out using the finite difference technique.
Hydrophobic magnetic nanoparticles (NPs) consisting of undecanoate-capped magnetite (Fe3O4, average diameter ca. 5 nm) are used to control quantized electron transfer to surface-confined redox units and metal NPs. A two-phase system consisting of an aqueous electrolyte solution and a toluene phase that includes the suspended undecanoatecapped magnetic NPs is used to control the interfacial properties of the electrode surface. The attracted magnetic NPs form a hydrophobic layer on the electrode surface resulting in the change of the mechanisms of the surface-confined electrochemical processes. A quinone-monolayer modified Au electrode demonstrates an aqueous-type of the electrochemical process (2e-+2H+ redox mechanism) for the quinone units in the absence of the hydrophobic magnetic NPs, while the attraction of the magnetic NPs to the surface results in the stepwise single-electron transfer mechanism characteristic of a dry nonaqueous medium. Also, the attraction of the hydrophobic magnetic NPs to the Au electrode surface modified with Au NPs (ca. 1.4 nm) yields a microenvironment with a low dielectric constant that results in the single-electron quantum charging of the Au NPs.
Limit loads can be calculated with the finite element method (FEM) for any component, defect geometry, and loading. FEM suggests that published long crack limit formulae for axial defects under-estimate the burst pressure for internal surface defects in thick pipes while limit loads are not conservative for deep cracks and for pressure loaded crack-faces. Very deep cracks have a residual strength, which is modelled by a global collapse load. These observations are combined to derive new analytical local and global collapse loads. The global collapse loads are close to FEM limit analyses for all crack dimensions.
Traglast- und Einspielanalysen sind vereinfachte doch exakte Verfahren der Plastizität, die neben ausreichender Verformbarkeit keine einschränkenden Voraussetzungen beinhalten. Die Vereinfachungen betreffen die Beschaffung der Daten und Modelle für Details der Lastgeschichte und des Stoffverhaltens. Anders als die klassische Behandlung nichtlinearer Probleme der Strukturmechanik führt die Methode auf Optimierungsprobleme. Diese sind bei realistischen FEM-Modellen sehr groß. Das hat die industrielle Anwendung der Traglast- und Einspielanalysen stark verzögert. Diese Situation wird durch das Brite-EuRam Projekt LISA grundlegend geändert. Die Autoren möchten der Europäischen Kommission an dieser Stelle für die Förderung ausdrücklich danken. In LISA entsteht auf der Basis des industriellen FEM-Programms PERMAS ein Verfahren zur direkten Berechnung der Tragfähigkeit duktiler Strukturen. Damit kann der Betriebsbereich von Komponenten und Bauwerken auf den plastischen Bereich erweitert werden, ohne den Aufwand gegenüber elastischen Analysen wesentlich zu erhöhen. Die beachtlichen Rechenzeitgewinne erlauben Parameterstudien und die Berechnung von Interaktionsdiagrammen, die einen schnellen Überblick über mögliche Betriebsbereiche vermitteln. Es zeigt sich, daß abhängig von der Komponente und ihren Belastungen teilweise entscheidende Sicherheitsgewinne zur Erweiterung der Betriebsbereiche erzielt werden können. Das Vorgehen erfordert vom Anwender oft ein gewisses Umdenken. Es werden keine Spannungen berechnet, um damit Sicherheit und Lebensdauer zu interpretieren. Statt dessen berechnet man direkt die gesuchte Sicherheit. Der Post-Prozessor wird nur noch zur Modell- und Rechenkontrolle benötigt. Das Vorgehen ist änhlich der Stabilitätsanalyse (Knicken, Beulen). Durch namhafte industrielle Projektpartner werden Validierung und die Anwendbarkeit auf eine breite Palette technischer Probleme garantiert. Die ebenfalls in LISA geplante Zuverlässigkeitsanalyse ist erst auf der Basis direkter Verfahren effektiv möglich. Ohne Traglast- und Einspielanalyse ist plastische Strukturoptimierung auch heute kaum durchführbar.
Traglast- und Einspielanalysen sind vereinfachte doch exakte Verfahren der Plastizität, die neben ausreichender Verformbarkeit keine einschränkenden Voraussetzungen beinhalten. Die Vereinfachungen betreffen die Beschaffung der Daten und Modelle für Details der Lastgeschichte und des Stoffverhaltens. Anders als die klassische Behandlung nichtlinearer Probleme der Strukturmechanik führt die Methode auf Optimierungsprobleme. Diese sind bei realistischen FEM-Modellen sehr groß. Das hat die industrielle Anwendung der Traglast- und Einspielanalysen stark verzögert. Diese Situation wird durch das Brite-EuRam Projekt LISA grundlegend geändert. In LISA entsteht auf der Basis des industriellen FEM-Programms PERMAS ein Verfahren zur direkten Berechnung der Tragfähigkeit duktiler Strukturen. Damit kann der Betriebsbereich von Komponenten und Bauwerken auf den plastischen Bereich erweitert werden, ohne den Aufwand gegenüber elastischen Analysen wesentlich zu erhöhen. Die beachtlichen Rechenzeitgewinne erlauben Parameterstudien und die Berechnung von Interaktionsdiagrammen, die einen schnellen Überblick über mögliche Betriebsbereiche vermitteln. Es zeigt sich, daß abhängig von der Komponente und ihren Belastungen teilweise entscheidende Sicherheitsgewinne zur Erweiterung der Betriebsbereiche erzielt werden können. Das Vorgehen erfordert vom Anwender oft ein gewisses Umdenken. Es werden keine Spannungen berechnet, um damit Sicherheit und Lebensdauer zu interpretieren. Statt dessen berechnet man direkt die gesuchte Sicherheit. Der Post-Prozessor wird nur noch zur Modell- und Rechenkontrolle benötigt. Das Vorgehen ist ähnlich der Stabilitätsanalyse (Knicken, Beulen). Durch namhafte industrielle Projektpartner werden Validierung und die Anwendbarkeit auf eine breite Palette technischer Probleme garantiert. Die ebenfalls in LISA entwickelten Zuverlässigkeitsanalysen sind nichlinear erst auf der Basis direkter Verfahren effektiv möglich. Ohne Traglast- und Einspielanalyse ist plastische Strukturoptimierung auch heute kaum durchführbar. Auf die vorgesehenen Erweiterungen der Werkstoffmodellierung für nichtlineare Verfestigung und für Schädigung konnte hier nicht eingegangen werden. Es herrscht ein deutlicher Mangel an Experimenten zum Nachweis der Grenzen zwischen elastischem Einspielen und dem Versagen durch LCF oder durch Ratchetting.
The load-carrying capacity or the safety against plastic limit states are the central questions in the design of structures and passive components in the apparatus engineering. A precise answer is most simply given by limit and shakedown analysis. These methods can be based on static and kinematic theorems for lower and upper bound analysis. Both may be formulated as optimization problems for finite element discretizations of structures. The problems of large-scale analysis and the extension towards realistic material modelling will be solved in a European research project. Limit and shakedown analyses are briefly demonstrated with illustrative examples.
7th International Conference on Reliability of Materials and Structures (RELMAS 2008). June 17 - 20, 2008 ; Saint Petersburg, Russia. pp 354-358. Reprint with corrections in red Introduction Analysis of advanced structures working under extreme heavy loading such as nuclear power plants and piping system should take into account the randomness of loading, geometrical and material parameters. The existing reliability are restricted mostly to the elastic working regime, e.g. allowable local stresses. Development of the limit and shakedown reliability-based analysis and design methods, exploiting potential of the shakedown working regime, is highly needed. In this paper the application of a new algorithm of probabilistic limit and shakedown analysis for shell structures is presented, in which the loading and strength of the material as well as the thickness of the shell are considered as random variables. The reliability analysis problems may be efficiently solved by using a system combining the available FE codes, a deterministic limit and shakedown analysis, and the First and Second Order Reliability Methods (FORM/SORM). Non-linear sensitivity analyses are obtained directly from the solution of the deterministic problem without extra computational costs.
Limit and shakedown theorems are exact theories of classical plasticity for the direct computation of safety factors or of the load carrying capacity under constant and varying loads. Simple versions of limit and shakedown analysis are the basis of all design codes for pressure vessels and pipings. Using Finite Element Methods more realistic modeling can be used for a more rational design. The methods can be extended to yield optimum plastic design. In this paper we present a first implementation in FE of limit and shakedown analyses for perfectly plastic material. Limit and shakedown analyses are done of a pipe–junction and a interaction diagram is calculated. The results are in good correspondence with the analytic solution we give in the appendix.
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.
Herein, fibroin, polylactide (PLA), and carbon are investigated for their suitability as biocompatible and biodegradable materials for amperometric biosensors. For this purpose, screen-printed carbon electrodes on the biodegradable substrates fibroin and PLA are modified with a glucose oxidase membrane and then encapsulated with the biocompatible material Ecoflex. The influence of different curing parameters of the carbon electrodes on the resulting biosensor characteristics is studied. The morphology of the electrodes is investigated by scanning electron microscopy, and the biosensor performance is examined by amperometric measurements of glucose (0.5–10 mM) in phosphate buffer solution, pH 7.4, at an applied potential of 1.2 V versus a Ag/AgCl reference electrode. Instead of Ecoflex, fibroin, PLA, and wound adhesive are tested as alternative encapsulation compounds: a series of swelling tests with different fibroin compositions, PLA, and Ecoflex has been performed before characterizing the most promising candidates by chronoamperometry. Therefore, the carbon electrodes are completely covered with the particular encapsulation material. Chronoamperometric measurements with H2O2 concentrations between 0.5 and 10 mM enable studying the leakage current behavior.
Cement augmentation is an emerging surgical procedure in which bone cement is used to infiltrate and reinforce osteoporotic vertebrae. Although this infiltration procedure has been widely applied, it is performed empirically and little is known about the flow characteristics of cement during the injection process. We present a theoretical and experimental approach to investigate the intertrabecular bone permeability during the infiltration procedure. The cement permeability was considered to be dependent on time, bone porosity, and cement viscosity in our analysis. In order to determine the time-dependent permeability, ten cancellous bone cores were harvested from osteoporotic vertebrae, infiltrated with acrylic cement at a constant flow rate, and the pressure drop across the cores during the infiltration was measured. The viscosity dependence of the permeability was determined based on published experimental data. The theoretical model for the permeability as a function of bone porosity and time was then fit to the testing data. Our findings suggest that the intertrabecular bone permeability depends strongly on time. For instance, the initial permeability (60.89 mm4/N.s) reduced to approximately 63% of its original value within 18 seconds. This study is the first to analyze cement flow through osteoporotic bone. The theoretical and experimental models provided in this paper are generic. Thus, they can be used to systematically study and optimize the infiltration process for clinical practice.
Micromachined thermal heater platforms offer low electrical power consumption and high modulation speed, i.e. properties which are advantageous for realizing nondispersive infrared (NDIR) gas- and liquid monitoring systems. In this paper, we report on investigations on silicon-on-insulator (SOI) based infrared (IR) emitter devices heated by employing different kinds of metallic and semiconductor heater materials. Our results clearly reveal the superior high-temperature performance of semiconductor over metallic heater materials. Long-term stable emitter operation in the vicinity of 1300 K could be attained using heavily antimony-doped tin dioxide (SnO2:Sb) heater elements.
The propagation of mechanical waves in plates of isotropic elastic material is investigated. After a short introduction to the understanding of focussing of stress waves in a plate with a curved boundary the method of characteristics is applied to a plate of hyperelastic material. Using this method the propagation of acceleration waves is discussed. Based on this a numerical difference scheme is developed for solving initial-boundary-value problems and applied to two examples: propagation of a point disturbance in a homogeneously finitely strained non-linear elastic plate and geometrical focussing in al linear elastic plate.
An array of 50 MHz quartz microbalances (QMBs) coated with a dendronized polymer was used to detect small amounts of volatile organic compounds (VOCs) in the gas phase. The results were compared to those obtained with the commonly used 10 MHz QMBs. The 50 MHz QMBs proved to be a powerful tool for the detection of VOCs in the gas phase; therefore, they represent a promising alternative to the much more delicate surface acoustic wave devices (SAWs).