142 research outputs found
Resensies: Die Chacma-ekspedisie: Heling pleks van verdeling
No full textBook Title: Die Chacma-ekspedisie: Heling pleks van verdelingBook Author: Marius AckermannPretoria: Protea Boekhuis, 2016. 159 pp. ISBN: 978-1-4853-0626-9
Paleoproterozoic granulites from Heling'er: Implications for regional ultrahigh-temperature metamorphism in the North China Craton
No full textThe Inner Mongolia Suture Zone (IMSZ, incorporating the Khondalite Belt) forms part of an accretionary orogen developed during the Paleoproterozoic collision between the Yinshan Block and Ordos Blocks within the North China Craton (NCC). The granulites within the IMSZ are characterized by high-temperature (HT) to ultrahigh-temperature (UHT) metamorphism with diagnostic mineral assemblages for UHT conditions preserved in some localities such as Tuguiwula and Wuchuan. We report here a new locality in Heling'er, located within the southern domain of the IMSZ where spinel-garnet-sillimanite-bearing granulites record UHT metamorphic conditions. The prograde assemblages occurring as inclusions in porphyroblastic minerals in these rocks include sillimanite + quartz + spinet, whereas coarse grained garnet + sillimanite + quartz + spinel + cordierite + plagioclase + K-feldspar + magnetite + ilmenite represent the peak assemblages. The retrograde stage is marked by orthopyroxene and cordierite rims developed on garnet and spinel. Biotite marks the final hydration stage of the high-grade metamorphism. Spinel and quartz occur in direct contact, with the spinel showing low Zn. Cr, and Fe3+. Application of Ti-in-zircon and ternary feldspar geothermometers yields temperatures up to similar to 940 degrees C for the peak stage. Mineral phase equilibria modeling based on the bulk chemistry and mineral assemblages shows that the peak assemblage of garnet + plagioclase + spinet + cordierite + sillimanite + quartz + ilmenite + magnetite was stabilized at 1030 degrees C at 6.5-7.5 kbar, thus we infer a 940-1030 degrees C temperature range for peak metamorphism in these rocks. The newly discovered UHT rocks in Heling'er, dated as 1.92 Ga, together with the two previously reported UHT localities at Tuguiwula and Wuchuan, suggest that the Paleoproterozoic UHT metamorphism occurred on a regional scale within the IMSZ, probably in association with the subduction-accretion-collision tectonics and the incorporation of the NCC within the Columbia supercontinent. (C) 2012 Elsevier B.V. All rights reserved.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000308055800005&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Geochemistry & GeophysicsMineralogySCI(E)18ARTICLE54-7014
On the classification of convex lattice polytopes
No full textIn 1980, Arnold studied the classification problem for convex lattice polygons of given area. Since then this problem and its high dimensional analogue have been studied by Barany, Pach, Vershik and others. Bounds for the number of non-equivalent d-dimensional convex lattice polytopes of given volume have been achieved. In this paper we study Arnold's problem for centrally symmetric lattice polygons and the classification problem for convex lattice polytopes of given cardinality. In the plane we obtain analogues to the bounds of Arnold, Barany and Pach in both cases. However, the number of non-equivalent d-dimensional convex lattice polytopes of w lattice points is infinite whenever w - 1 >= d >= 3, which may intuitively contradict to Barany and Vershik's upper bound.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000296963800010&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701MathematicsSCI(E)2ARTICLE4711-7291
Design of cold chain logistics remote monitoring system based on ZigBee and GPS location
No full textSimulatie van botingroei in een prothese
No full textEen botbreuk is een veelvoorkomende verwonding aan het lichaam en over het algemeen geneest deze breuk zonder enige complicaties. Echter in 10% van de gevallen leiden complicaties tot vertraagde en misvormde heling van het bot. Door middel van mechanische stimulatie kan botgroei worden bevorderd en dus het helen van de botbreuk worden versneld. Een wiskundig model van botheling waarin deze stimulatie is verwerkt zou meer inzicht kunnen geven in het helen van de botbreuk. Zo een model is onderzocht in deze thesis.Electrical Engineering, Mathematics and Computer Scienc
Einsatz und Validierung virtueller Absicherungsmethoden für abweichungsbehaftete Mechanismen im Kontext des Robust Design
No full textManufacturing processes are inevitably subject to variations that cause the quality of manufactured products to vary. Since quality fluctuations have a negative impact on the properties of products, Robust Design aims to minimize fluctuations. To accomplish this goal, various virtual validation tools can be used during product development.
In the context of this work, a holistic approach model is presented that provides a framework for the systematic use and validation of virtual validation methods. This novel approach enables the targeted use of different virtual validation tools that can be applied during product development. Furthermore, for the first time it is shown how tolerance analysis models for mechanisms can be validated.
Product developers are thus provided with a generally applicable, adaptable approach that enables them to use virtual validation methods in a systematic way and to critically evaluate their validity with the help of validations.
The author also demonstrates how the procedure model can be adapted to practical problems. This is illustrated using the kinematics of an X-ray shutter, which serves as a demonstrator.Fertigungsprozesse unterliegen zwangsläufig Schwankungen, die dazu führen, dass die Qualität gefertigter Produkte variiert. Da sich Qualitätsschwankungen negativ auf die Eigenschaften von Produkten auswirken, strebt das Robust Design eine Minimierung der Schwankungen an. Um dieses Ziel zu erreichen, können während der Produktentwicklung unterschiedliche virtuelle Absicherungswerkzeuge eingesetzt werden.
Im Rahmen dieser Arbeit wird ein holistisches Vorgehensmodell präsentiert, das als Rahmenwerk für den systematischen Einsatz und die Validierung von virtuellen Absicherungsmethoden dient. Dieses neuartige Vorgehen ermöglicht den zielgerichteten Einsatz unterschiedlicher virtueller Absicherungswerkzeuge, die während der Produktentwicklung eingesetzt werden. Darüber hinaus wird erstmalig aufgezeigt, wie Toleranzanalysemodelle für Mechanismen validiert werden können.
Produktentwicklern wird damit ein allgemeingültiger, anpassbarer Ansatz zur Verfügung gestellt, der sie befähigt virtuelle Absicherungsmethoden zielgerichtet einzusetzen und deren Aussagekraft mit Hilfe von Validierungen kritisch zu bewerten.
Der Autor zeigt darüber hinaus, wie das Vorgehensmodell an praxisrelevante Problemstellungen angepasst werden kann. Anhand der Kinematik einer Röntgenblende, die als Demonstrator dient, wird dies veranschaulicht
Three-dimensional electronic scaffolds for monitoring and regulation of multifunctional hybrid tissues
No full textRecently, the integration of electronic elements with cellular scaffolds has brought forth the ability to monitor and control tissue function actively by using flexible free-standing two-dimensional (2D) systems. Capabilities for electrically probing complex, physicochemical and biological three-dimensional (3D) microenvironments demand, however, 3D electronic scaffolds with well-controlled geometries and functional-component distributions. This work presents the development of flexible 3D electronic scaffolds with precisely defined dimensions and microelectrode configurations formed using a process that relies on geometric transformation of 2D precursors by compressive buckling. It demonstrates a capability to fabricate these constructs in diverse 3D architectures and/or electrode distributions aimed at achieving an enhanced level of control and regulation of tissue function relatively to that of other approaches. In addition, this work presents the integration of these 3D electronic scaffolds within engineered 3D cardiac tissues, for monitoring of tissue function, controlling tissue contraction through electrical stimulation, and initiating on-demand, local release of drugs, each through well-defined volumetric spaces. These ideas provide opportunities in fields ranging from in vitro drug development to in vivo tissue repair and many others
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