A new load cell for measuring normal and shear stresses

A special stress measuring device for determining the normal and shear stresses acting on silo walls was developed and tested. The load cell can be used for measuring simultaneously the normal stress as well as the intensity and direction of the shear stress.     

Phase Transformation Modelling and Parameter Identification from Dilatometric Investigations

The goal of this paper is to propose a new approach towards the evaluation of dilatometric results, which are often employed to analyse the phase transformation kinetics in steel, especially in terms of continuous cooling transformation (CCT) diagram. A simple task of dilatometry is deriving the start and end temperatures of the phase transformation. It can yield phase transformation kinetics provided that plenty metallographic investigations are performed, whose analysis is complicated especially in case of several coexisting product phases. The new method is based on the numerical solution of a thermomechanical identification problem. It is expected that the phase transformation kinetics can be derived by this approach with less metallographic tasks. The first results are remarkably promising although further investigations are required for the numerical simulations.     

Biodegradable polymers applied in tissue engineering research: a review

Typical applications and research areas of polymeric biomaterials include tissue replacement, tissue augmentation, tissue support, and drug delivery. In many cases the body needs only the temporary presence of a device/biomaterial, in which instance biodegradable and certain partially biodegradable polymeric materials are better alternatives than biostable ones. Recent treatment concepts based on scaffold‐based tissue engineering principles differ from standard tissue replacement and drug therapies as the engineered tissue aims not only to repair but also regenerate the target tissue. Cells have been cultured outside the body for many years; however, it has only recently become possible for scientists and engineers to grow complex three‐dimensional tissue grafts to meet clinical needs. New generations of scaffolds based on synthetic and natural polymers are being developed and evaluated at a rapid pace, aimed at mimicking the structural characteristics of natural extracellular matrix. This review focuses on scaffolds made of more recently developed synthetic polymers for tissue engineering applications. Currently, the design and fabrication of biodegradable synthetic scaffolds is driven by four material categories: (i) common clinically established polymers, including polyglycolide, polylactides, polycaprolactone; (ii) novel di‐ and tri‐block polymers; (iii) newly synthesized or studied polymeric biomaterials, such as polyorthoester, polyanhydrides, polyhydroxyalkanoate, polypyrroles, poly(ether ester amide)s, elastic shape‐memory polymers; and (iv) biomimetic materials, supramolecular polymers formed by self‐assembly, and matrices presenting distinctive or a variety of biochemical cues. This paper aims to review the latest developments from a scaffold material perspective, mainly pertaining to categories (ii) and (iii) listed above. Copyright © 2006 Society of Chemical Industry     

Die Bewertung von Kreditgarantien mittels Hyperoptionen

Zusammenfassung. Aus finanzwirtschaftlicher Sicht k?nnen Kreditgarantien als Verkaufsoptionen auf das anteilige Gesamtverm?gen einer Unternehmung interpretiert werden. Die Bewertung von Kreditgarantien erfolgt üblicherweise mit dem Ansatz von Merton. Bei diesem Modell wird jedoch unterstellt, da? sowohl für den garantierten Kredit als auch für das nicht garantierte Fremdkapital vor Ablauf der Laufzeit keinerlei Zins– und Tilgungszahlungen geleistet werden. Unsere Arbeit pr?sentiert ein Modell zur Bewertung von Garantien auf Kredite mit beliebigen Zins– und Tilgungsmodalit?ten. Das vorgeschlagene Bewertungsmodell wird auf Kredite mit unterschiedlichen Tilgungsformen angewendet. Darüber hinaus werden Sensitivit?tsanalysen bezüglich der Einflu?faktoren auf die aus dem Modell resultierenden Pr?miens?tze durchgeführt. Eingegangen: 2. Februar 1999 / Angenommen: 9. Dezember 1999     

Non-polymeric binders for ceramic powders: utilization of neutral and ionic species derived from decaborane(14)

The pyrolytic conversion of bis-Lewis base adducts of decaborane(14), L·B₁₀H₁₂·L (L=neutral monophosphine) and phosphonium salts of the [B₁₀H₁₀]^2– anion (e.g. [Ph₄P⁺]₂, etc.), to ceramic materials has been studied. All species examined served as binders for a variety of non-oxide refractory ceramic powders (e.g. B₄C, BN, BP, B₁₃P₂, SiC, Si₃N₄, B, C, AIN).     

Temperature‐dependent coefficient of thermal expansion (CTE) of injection molded,short‐glass‐fiber‐reinforced polymers

A deep understanding of the anisotropic, composite‐, geometry‐, and temperature‐dependent coefficient of thermal expansion (CTE) of short‐fiber‐reinforced polymers is often needed in material development and at early stages of the design process of injection molded parts. Usually, the data available does not reflect the complex behavior and the knowledge about the influences and interactions are missing. This paper deals with a method for calculating the composite‐, geometry‐, and temperature‐dependent anisotropic CTE of parts made from short‐fiber reinforced polymers without respectively low preload to create an understanding of its origins and influential factors. Here, a good accordance between the measurements and calculations was achieved. POLYM. ENG. SCI., 55:2661–2668, 2015. © 2015 Society of Plastics Engineers     

Methoden zur Analyse des Bruchverhaltens hochfester Stahlfaserbetone

Methods for analyzing the fracture behavior of high‐strength steel fiber‐reinforced concretes High‐strength and ultra‐high strength fiber‐reinforced concretes are most suitable for applications with extreme mechanical loads. These extreme conditions require a ductile behavior under tensile loading, which is obtained solely by the addition of steel fibers and their working mechanism. Profound know ledge on the working mechanism of the steel fibers is necessary for optimizing this material. Usually, this knowledge is obtained by means of classical measuring techniques of destructive tests. Adopting measuring techniques from non‐destructive material testing helps to analyze and to identify the different stages of the fracture mechanism of high‐strength and ultra‐high strength fiber‐reinforced concretes in detail. The application of different non‐destructive measuring techniques is shown exemplary on tensile tests conducted on an ultra‐high strength fiber‐reinforced concrete and its applicability for analyzing the fracture behavior is discussed. The main focus is on the characterization of the relevant failure modes under tensile loading by the different measuring techniques and the comparison with classical measuring techniques (e. g. extensometer). The tensile tests have been analyzed by optical deformation measurements using digital image correlation (DIC), acoustic emission analysis (AE), and 3D computed tomography (CT).     

Transient and steady-state analysis of catalyst poisoning and mixed potential formation in direct methanol fuel cells

The present dynamic model is developed to investigate the coupled reaction mechanisms in a DMFC and therein associated voltage losses in the catalyst layers. The model describes a complete five-layer membrane electrode assembly (MEA), with gas diffusion layers, catalyst layers and membrane. The analysis of the performance losses are mainly focused on the electrochemical processes. The model accounts for the crossover of both, methanol from anode to cathode and oxygen from cathode to anode. The reactant crossover results in parasitic internal currents that are finally responsible for high overpotentials in both electrodes, so-called mixed potentials. A simplified and general reaction mechanism for the methanol oxidation reaction (MOR) was selected, that accounts for the coverage of active sites by intermediate species occurring during the MOR. The simulation of the anode potential relaxation after current interruption shows an undershoot behavior like it was measured in the experiment [1]. The model gives an explanation of this phenomenon by the transients of reactant crossover in combination with the change of CO and OH coverages on Pt and Ru, respectively.     

Comparison of fatty acid profiles and contents of seed oils recovered from dessert and cider apples and further Rosaceous plants

To get a more comprehensive knowledge of oil contents and fatty acid pattern, seed oils from various Rosaceous plants belonging to the subfamilies Maloideae and Rosoideae, respectively, were investigated. For this purpose, isolated seeds of 18 dessert and cider apple (Malus domestica BORKH.) cultivars of different provenances, pear (Pyrus communis L.), rose hip (Rosa canina L.), quince (Cydonia oblonga Mill.), and red chokeberry (Aronia arbutifolia L.) were analyzed for their oil content and fatty acid composition. Oil contents varied significantly, not only among the different genera, but also among cultivars of one species, ranging from 0.8 to 29.4?g/100?g?dry matter. Qualitatively, the fatty acid profiles of the investigated seed oils showed good agreement in all representatives of the Rosaceae. Their triacylglycerols were uniformly composed of linoleic, oleic, palmitic, stearic, palmitoleic, α-linolenic, arachidic, gondoic, and behenic acids. Quantitation of individual fatty acids revealed the oils to be rich in mono- and diunsaturated oleic acid and linoleic acid, ranging from 15.1 to 33.3?g/100?g and from 32.5 to 49.7?g/100?g, respectively. As expected, contents of saturated fatty acids were 6–10?times lower. Moreover, apple cultivars showed pronounced differences in yields, numbers, and weights of their seeds. As demonstrated by the data obtained from this study, seeds resulting from the processing of apple, pear, quince, chokeberry (Maloideae), and rose hip (Rosoideae) into juices, jellies, and jams may serve as a promising source for the recovery of nutritionally valuable edible oils.