1D HERMITE ELEMENTS FOR C1-CONTINUOUS SOLUTIONS IN SECOND GRADIENT ELASTICITY

We present a modified strain gradient theory of elasticity for linear isotropic materials in order to account for the so-called size effect. Additional material length scale parameters are introduced and the problem of static beam bending is analyzed. A numerical solution is derived by means of a finite element approach. A global C1-continuous displacement field is applied in finite element solutions because the higher-order strain energy density additionally depends on second gradients of displacements. So-called Hermite finite elements are used that allow for merging gradients between elements. The element stiffness matrix as well as the global stiffness matrix of the problem is developed. Convergence, C1-continuity and the size effect in the numerical solution is shown. Experiments on bending stiffnesses of different sized micro beams made of the polymer SU-8 are performed by using an atomic force microscope and the results are compared to the numerical solution

High-Temperature Heat Pump for Wellness Applications Using CO2 as a Refrigerant

Building technology recently has been affected by great innovations to reduce energy demand and to enable self-sufficient operation. To test innovations and prove practicality, EMPA has built a research building called NEST, where different demonstration projects from the building industry can be integrated and scientifically monitored. Furthermore, the sector of wellness applications shows significant potential for improving energy efficiency. Usually, spa facilities such as saunas and steam baths are based on direct electric or fossil heating which is extremely energy intensive and results in high operating costs. In order to establish a more energy efficient technology to provide heat to wellness areas, the present work proposes the usage of a high temperature heat pump with CO2 as a refrigerant. Carbon dioxide is currently favored by many heat pump applications due to the demand for low-GWP refrigerants with non-toxic and non-flammable properties. High-temperature heat pumps with CO2 as a refrigerant are already available on the market and reach supply temperatures typically up to 100 °C. Wellness applications require temperatures up to 130 °C on the supplier side, which requires new system design. On the consumption side, the heat will be used on a wide variety of temperature levels considering different saunas, showers and space heating. In this context, a stratified storage system ensures the heat output on the desired temperature level. Therefore, the heat exchanger unit as well as the operating range of the heat pump are the major challenges. In Coorporation with Scheco AG, a new CO2 refrigerant system has been designed and set up as a part of EMPA research building by means of a pilot installation including different saunas, steam bath and showers. Measurements will be performed as soon as possible to start the optimization process of the system

Circulating endothelial cells demonstrate an attenuation of endothelial damage by minimizing the extracorporeal circulation

ObjectiveDetachment of endothelial cells may represent serious injury of the endothelium after cardiopulmonary bypass. We investigated whether the extent of endothelial injury is related to the type of cardiopulmonary bypass system used (conventional or minimized) and determined circulating endothelial cells as well as von Willebrand factor and soluble thrombomodulin.MethodsTwenty patients scheduled for elective coronary bypass grafting were randomly assigned to either the minimal extracorporeal circulation system or the standard cardiopulmonary bypass. Ten healthy volunteers served as controls. Circulating endothelial cells per milliliter of full blood were perioperatively determined by immunomagnetic cell separation technique. Endothelial plasma markers were measured by enzyme-linked immunosorbent assay.ResultsPreoperative circulating endothelial cell numbers did not differ between the experimental groups, but were significantly higher than in the healthy controls (18.6 ± 5.6 vs 7.2 ± 3.8, P < .001). At 6 hours, circulating endothelial cell numbers increased significantly compared with baseline in both experimental groups and peaked at 12 hours after cardiopulmonary bypass initiation, each time with significantly lower values in the minimal extracorporeal circulation group (6 hours: 44.0 ± 9.9 vs 29.6 ± 9.8, P = .007; 12 hours: 48.1 ± 6.8 vs 31.8 ± 7.1, P < .001). Likewise, von Willebrand factor and soluble thrombomodulin postoperatively increased in both groups with a tendency toward lower levels in the minimal extracorporeal circulation group. Although circulating endothelial cells gradually declined, continually with lower numbers in the minimal extracorporeal circulation group, the endothelial plasma markers remained elevated during observation time.ConclusionsCirculating endothelial cells represent a novel marker of the intrinsic endothelial damage caused by cardiopulmonary bypass. Its analysis facilitates the evaluation of cardiopulmonary bypass modifications as the minimal extracorporeal circulation system could be proven to be less injurious to endothelium and myocardium

Validation of a Simulation Methodology for Thermoplastic and Thermosetting Composite Materials Considering the Effect of Forming Process on the Structural Performance

This research work investigated the influence of the press molding manufacturing process on the mechanical properties, both for thermoplastic and thermosetting fiber reinforced composite materials. The particular geometry of the case study, called Double Dome, was considered in order to verify the behavior of the Thermoplastic and Thermosetting prepreg in terms of shell thickness variation and fibers shear angle evolution during the thermoforming process. The thermoforming simulation was performed using LS-DYNA Finite Element Analysis (FEA) code, and the results were transferred by Envyo, a dedicated mapping tool, into a LS-DYNA virtual model for the structural simulation. A series of Double Dome specimens was produced with industrial equipment, and a bending experimental test was been carried on. Finally, a numerical-experimental correlation was performed, highlighting a significant forecast of the mechanical properties for the considered component

Effect of acute kidney injury requiring extended dialysis on 28 day and 1 year survival of patients undergoing interventional lung assist membrane ventilator treatment

<p>Abstract</p> <p>Background</p> <p>Extracorporeal lung assist devices are increasingly used in the intensive care unit setting to improve extracorporeal gas exchange mainly in patients with acute respiratory distress syndrome. ARDS is frequently accompanied by acute kidney injury; however it is so far unknown how the combination of these two conditions affects long term survival of critically ill patients.</p> <p>Methods</p> <p>In a retrospective analysis of a tertiary care hospital we evaluated all patients undergoing interventional lung assist (iLA) treatment between January 1^st2005 and December 31^st2009. Data from all 61 patients (31 F/30 M), median age 40 (28 to 52) years were obtained by chart review. Follow up data up to one year were obtained.</p> <p>Results</p> <p>Of the 61 patients undergoing iLA membrane ventilator treatment 21 patients had acute kidney injury network (AKIN) stage 3 and were treated by extended dialysis (ED). Twenty-eight day survival of all patients was 33%. While patients without ED showed a 28 day survival of 40%, the survival of patients with ED was only 19%. Patients on ED were not different in respect to age, weight, Horowitz index and underlying disease.</p> <p>Conclusions</p> <p>AKI requiring ED therapy in patients undergoing iLA treatment increases mortality in ICU patients. Patients in whom iLA was placed as a bridge to lung transplantation and that were successfully transplanted showed the best outcome. Future studies have to clarify whether it is possible to identify patients that truly benefit from the combination of these two extracorporeal treatment methods.</p

Acute Muscular Sarcocystosis: An International Investigation Among Ill Travelers Returning From Tioman Island, Malaysia, 2011-2012

A large outbreak of acute muscular sarcocystosis (AMS) among international tourists who visited Tioman Island, Malaysia, is described. Clinicians evaluating travelers returning ill from Malaysia with myalgia, with or without fever, should consider AMS in their differential diagnosi

Size effect in elasticity : experimental, analytical and numerical investigations

A continual miniaturization of mechanical components requires refined mathematical models and the knowledge of the respective additional material parameters. If the outer dimensions arrive at the size of an internal inhomogeneity of the material, the influence of the internal structure has to be addressed by appropriate homogenization methods. Generalized continuum theories can be used in order not to lose the benefits of continuity of matter. This work will present analytical as well as numerical models, which achieve a smooth transition in the dependence of the material characteristics of different scales. The method of size effect is applied to bending rigidities of beam structures and selected higher order material constants are measured in own experiments at varying outer dimensions. In the context of linear elasticity theory, the elastic modulus of the materials: SU-8, epoxy, silicon, silicon nitride, aluminum foam and aluminum with artificially heterogeneities are investigated using at least three different sample sizes, respectively. The size effect, that significantly occurs in the analysis of flexural frequencies and in bending tests in an atomic force microscope, is modeled by advanced continuum theories (micropolar theory, couple stress theory, strain gradient theory and surface elasticity theory) and higher order material parameters are extracted. Mechanical strains, which occur in the surface of the bend silicon micro-cantilevers were determined with the help of micro-RAMANspectroscopy and the laser penetration depth was quantified using the size-dependent behavior of the strain values. Higher order theories as well as experimental apparatuses will be discussed and details in their application will be presented. As a result, bending rigidities of SU-8 and epoxy increase by the factor of 1.6 and 2.1, respectively, while beam thicknesses decrease.Eine fortlaufende Miniaturisierung mechanischer Bauteile erfordert verfeinerte Berechnungsmodelle und die Kenntnis darin enthaltener erweiterter Werkstoffparameter. Erreichen äußere Abmaße die Größenordnung der inneren Struktur des Materials, so kann der Einfluss des inneren Aufbaus durch geeignete Homogenisierungsverfahren berücksichtigt werden. Um dabei nicht die Vorteile der Kontinuität der Materie zu verlieren, werden sog. generalisierte Kontinuums-modelle vorgestellt, die es ermöglichen, analytisch, als auch numerisch fließende Übergänge in der Abhängigkeit der Materialcharakteristika abzubilden. In Experimenten zur Biegesteifigkeit von Balkenstrukturen wird die Methode des Größeneffekts angewendet, wonach ausgewählte Materialkonstanten bei sich ändernden äußeren Abmaßen auf konventioneller Basis gemessen werden. Im Umfeld der linearen Elastizitätstheorie werden in dieser Arbeit die Elastizitäts-, bzw. Strukturmoduln für die Werkstoffe: SU-8 (ein epoxidbasierter nagativ-Fotolack), Epoxidharz, einkristallines Silizium, amorphes Siliziumnitrid, verschiedene Aluminiumschäume und künstlich heterogenisiertes Aluminium in jeweils mindesten drei verschiedenen Probengrößen mit unterschiedlicher Balkenhöhe untersucht. Die in Frequenzanalysen und atomkraftmikroskopischen Versuchen teils deutlich auftretenden Größeneffekte im elastischen Bereich werden mit Hilfe erweiterter Kontinuumstheorien (Mikropolartheorie, Momentenspannungstheorie, Dehnungsgradiententheorie und Oberflächenelastizitätstheorie) modelliert und der jeweils höhere Materialparameter extrahiert. Mit Hilfe der Mikro-RAMANspektroskopie werden die auftretenden Biegedehnungen in der Oberfläche von einkristallinem Silizium bestimmt und die Lasereindringtiefe über die größenabhängigen Messwerte quantifiziert. Die erweiterten Theorien sowie die experimentellen Apparaturen werden in ihrem Wesen besprochen und ihre Details in der Anwendung dargelegt. Im Ergebnis stehen mit der Größe abweichende Biegesteifigkeiten des SU-8s und Epoxidharzes um das 1,6- bzw. 2,1-fache im Vergleich zur konventionellen Theorie.DFG, MU 1752/33-1, Größeneffektmodellierung mit der Strain-Gradient-Theorie und Bestimmung innerer Längenparameter in Silizium mittels Ramanspektroskopi

Verwendung des Digitalen Prototyp für eine geschlossene Simulationsprozesskette und Datenmanagement

Since about three years, DigitPro, a sub-project of the government funded research project Active Research Environment for the Next generation of Automobile (ARENA2036) works on the development of a Digital Prototype, a closed simulation process chain which not only covers different simulation disciplines such as crushing or process analysis, but also various material modeling approaches on the micro-, meso-, and macro level. Various software tools are being used by the project partners, namely the German Aerospace Center (DLR), the Institute of Textile Technology and Process Engineering (ITV), and the Institute of Aircraft Design (IFB) at the University of Stuttgart. The Digital Prototype allows the project partners to exchange data from the different simulation programs being used; utilizing the open source HDF5 binary data format and makes the data available for further analysis with an implemented data mapping process. This mapping algorithm allows the transfer of information from the process simulation to the structural analysis, the homogenization and clustering of material parameter being generated with the use of representative volume elements (RVE) and the automation of predefined simulation processes including optimization loops for the most important manufacturing parameters. Within this presentation, current developments of the Digital Prototype will be introduced and the influence of a closed simulation process chain will be shown

Investigating the influence of local fiber architecture in textile composites by the help of a mapping tool

Standard approaches for the modelling and simulation of composite structures rely on the homogenisation of material properties on unidirectional plies. Doing so, simulations lose the ability to precisely describe local phenomena and complex failure mechanisms. In the research campus ARENA2036, the project DigitPro (Digital Prototype) develops a method based on a closed simulation process chain to take into account potential production effects by braided or woven composite structures. Starting from the process simulation, crucial information like fibre orientation and waviness is mapped on a target mesh for structural analysis. The resulting model is then investigated and potential needs to change the component’s geometry or the manufacturing process are detected. The mapping tool Envyo, developed at DYNAmore, offers various possibilities for the transfer of information generated from process simulation. Thus, it is necessary to investigate the impact of mapping algorithms and respective parameters on the structure simulation. The present paper details the mapping procedure for textile composites. The influence of local fibre architecture is finally investigated on a generic structure and compared to a standard approach