bluuebunny/crossref_metadata_2025_split huggingface dataset:
13C CP/MAS NMR studies of morphological changes in polypropylene: 1—Annealing of quenched films
Authors: Caldas V. , Morin F. G. , Brown G. R. 
Published: April 2014

AbstractHigh‐resolution 13C cross‐polarization/magic angle spinning (CP/MAS) spectra of the crystalline component of quench‐cooled isotactic polypropylene (iPP) were obtained by using a pulse sequence that incorporates a delay period with a reduced spin locking field prior to cross‐polarization, thus exploiting the differences in 1H T1p relaxation times between the various phases. The spectra of samples annealed at high temperature have resolved splitting, ranging between 0.2 and 1.1 ppm, for all carbon resonances. The methyl resonance is composed of three resolved peaks whose relative areas, as obtained through peak deconvolution, depend on the anneal temperature. Large changes in these peak areas coincide with an exothermic transition observed by differential scanning calorimetry. The spectra of the interfacial and amorphous phases, obtained by subtraction, indicate a reduction in the amorphous content at anneal temperatures >100°C while the interfacial component appears to increase owing to recrystallization and the formation of more amorphous/crystal interfaces.
Determination of the reactivity ratios, sequence distribution and stereoregularity of butyl acrylate‐methyl methacrylate copolymers by means of proton and carbon‐13 NMR
Authors: Aerdts A. M. , German A. L. , van der Velden G. P. M. 
Published: April 2014

AbstractThe 400 MHz proton NMR spectra of butyl acrylate (BA)—methyl methacrylate (MMA) copolymers prepared by free radical polymerization in solution at 323 K were used for the determination of the reactivity ratios. The reactivity ratios rM and rB calculated by the error‐in‐variables method are 2.279 and 0.395, respectively. The methoxy region of the MMA proton signal resonance was found to be sensitive for MMA‐centred sequences and a new assignment is proposed. The coisotacticity parameter σBM was calculated using a non‐linear least‐squares procedure with relative error estimation based on the new assignment and was found to be 039. The carbon‐13 NMR spectra of the BA‐MMA copolymers, in particular the carbonyl signal resonances, are sensitive for MMA‐and BA‐centred configurational sequences. The same assignment is used as for the ethyl acrylate—methyl methacrylate copolymer.
A robust and efficient substepping scheme for the explicit numerical integration of a rate‐dependent crystal plasticity model
Authors: Zhang K. , Hopperstad O. S. , Holmedal B. , Dumoulin S. 
Published: April 2014

SUMMARYThis paper describes the development of efficient and robust numerical integration schemes for rate‐dependent crystal plasticity models. A forward Euler integration algorithm is first formulated. An integration algorithm based on the modified Euler method with an adaptive substepping scheme is then proposed, where the substepping is mainly controlled by the local error of the stress predictions within the time step. Both integration algorithms are implemented in a stand‐alone code with the Taylor aggregate assumption and in an explicit finite element code. The robustness, accuracy and efficiency of the substepping scheme are extensively evaluated for large time steps, extremely low strain‐rate sensitivity, high deformation rates and strain‐path changes using the stand‐alone code. The results show that the substepping scheme is robust and in some cases one order of magnitude faster than the forward Euler algorithm. The use of mass scaling to reduce computation time in crystal plasticity finite element simulations for quasi‐static problems is also discussed. Finally, simulation of Taylor bar impact test is carried out to show the applicability and robustness of the proposed integration algorithm for the modelling of dynamic problems with contact. Copyright © 2014 John Wiley & Sons, Ltd.
Controllability of impulsive mixed type Volterra–Fredholm stochastic systems with nonlocal conditions
Authors: Zhang Shuorui , Sun Jitao 
Published: April 2014

SummaryThis paper investigates complete controllability of impulsive mixed type Volterra–Fredholm stochastic systems with nonlocal conditions. Sufficient conditions are established for complete controllability of a class of impulsive stochastic integrodifferential systems with nonlocal conditions. The results are obtained by a fixed point approach on condition that the corresponding linear system is completely controllable. Finally, an example is given to illustrate our results. Copyright © 2014 John Wiley & Sons, Ltd.
Direct adaptive control for a class of discrete‐time unknown nonaffine nonlinear systems using neural networks
Authors: Yang Xiong , Liu Derong , Wei Qinglai , Wang Ding 
Published: April 2014

SummaryIn this paper, a direct adaptive state‐feedback control approach is developed for a class of nonlinear systems in discrete‐time (DT) domain. We study MIMO unknown nonaffine nonlinear DT systems and employ a two‐layer NN to design the controller. By using the presented method, the NN approximation is able to cancel the nonlinearity of the unknown DT plant. Meanwhile, pretraining is not required, and the weights of NNs used in adaptive control are directly updated online. Moreover, unlike standard NN adaptive controllers yielding uniform ultimate boundedness results, the tracking error is guaranteed to be uniformly asymptotically stable by utilizing Lyapunov's direct method. Two illustrative examples are provided to demonstrate the effectiveness and the applicability of the theoretical results. Copyright © 2014 John Wiley & Sons, Ltd.
Modell für den nachgiebigen Randverbund von Mehrscheiben‐Isoliergläsern
Authors: Ensslen Frank , Becker Heinz‐Rainer , Wittwer Wolfgang 
Published: April 2014

AbstractDer Randverbund von Isoliergläsern unterliegt hohen Anforderungen. Die Primärdichtstufe ist für die Dauerhaftigkeit des Systems hinsichtlich einer geringen Feuchtigkeitsaufnahme bzw. Gasverlustrate verantwortlich. Die Sekundärdichtstufe dient der Stabilität und dem Zusammenhalt der Gläser unter statischen sowie klimatisch induzierten Lasten. Die Funktionsweise des zweistufigen Randverbunds beruht auf dem komplexen Zusammenspiel zweier Polymerwerkstoffe und einem Abstandhalter. Der Beitrag beschreibt einen empirischen Ansatz: Auf Basis genauer Vermessung der Verformung verschiedener Probekörper unter definiert einwirkenden Lasten erfolgt die Bereitstellung einer Datenbasis, welche im Weiteren zur Ermittlung mechanischer Kenngrößen eines Federmodelles für den Randverbund herangezogen wird. Dieses Modell wird in FE‐Studien verwendet und mit dem üblichen, auf der Plattentheorie basierenden Rechenmodell verglichen.Model for the Elastic Edge Seal of Insulating Glass Units. The edge seal of Insulating Glass Units (IGU) is exposed to demanding conditions. The primary seal contributes mainly to the durability of the system with respect to its low moisture penetration and very low gas loss rates. The secondary seal provides mechanical fixing and stability of the glass assembly under static and climatic loads. The functionality of the dual seal is the result of a complex interaction of two polymeric materials and the spacer bar. This study describes an empirical approach: Based on the precise measurement of deformation under several well‐defined load scenarios of specimen modelling the edge seal, the data base gained is used to calibrate the springs of a suited mechanical model of IGU’s edge seal. The model is used in FE studies and results compared with conventional plate theory based modelling.Schlagwörter: Isolierglasrandverbund, Versiegelung, Randlast, Federkennlinie, Polymermechanik, Polymerversuche, viskoelastisches Verhalten, Plattenmodell
Energetische Sanierung Hypo Hochhaus – Gebogene 3‐fach Isolierverglasung der neuen Doppelfassade
Authors: Siebert Barbara , Herrmann Tobias 
Published: April 2014

AbstractDas 1981 fertiggestellte Hypo Hochhaus, mittlerweile ein Wahrzeichen der Stadt München, wird derzeit umfangreich saniert und zu einem “green building“ umgestaltet. Hierzu gehört auch die Umwandlung der alten Elementfassade in eine moderne Doppelfassade. Dies geschieht unter strengen Auflagen des Denkmalschutzes: das äußere Erscheinungsbild muss unverändert bleiben. Eine Besonderheit sind die eng gebogenen Dreifach‐Isolierverglasungen an den Gebäudeecken, welche nur teilweise durch die aktuellen Regelungen der TRLV bzw. der DIN 18008 abgedeckt sind.Energy Efficient Rehabilitation of the Hypo Hochhaus – Curved Triple Insulation Glass Unit of the New Double Skin Facade. The high rised building of “Hypo‐Vereinsbank” in Munich, erected 1981 and a landmark in Munich is at present under rehabilitation. To get a green building, amongst other topics the old facade is replaced by a modern double skin facade. The building is classified as a historic monument, meaning that renovation is subject to strict conditions. The outer appearance of the building has to remain unchanged. Remarkable features of the building are the curved insulation glass units at the edges, which are only partially covered by the German regulations for glass.
Fassaden, Glasbauplanung in China
Authors: Lutz Martin , Schenke David 
Published: April 2014

AbstractDer größte Wachstumsmarkt der Welt sichert dem Exportland Deutschland eine anhaltende Wirtschaftsstabilität. 50 % des Weltbauvolumens der nächsten 10 bis 15 Jahre werden in China realisiert. Der Bauboom setzt sich in den uns weitgehend unbekannten 20 bis 30 “Kleinstädten” mit 5 bis 10 Millionen Einwohnern fort. Eine Chance für deutsche Architektur‐ und Engineering‐Büros. Der Beitrag zeigt auf, welche Chancen der chinesische Fassaden‐ und Glasbaumarkt bietet, ebenso was in China möglich ist und was nicht möglich ist, dies sowohl theoretisch als auch anhand von geplanten Beispielprojekten in China.Facades, glass construction in China. The world’s largest emerging market secures a lasting stability for Germany’s export economy. 50 % of the global construction activity of the coming 10 to 15 years will take place in China. The construction boom continues in the 20 to 30 ‘smaller cities’ with 5 to 10 million inhabitants which are commonly unknown to us. This represents a chance for German architecture and engineering practices. The article outlines the chances which lie within the Chinese facade‐ and glass construction market and furthermore shows what is possible or impossible, in theory as well as by referring to practical examples of current design projects in China.
Aussteifende Holz‐Glas‐Fassaden – Aussteifungssysteme und Nachweise
Authors: Fadai1 Alireza , Winter Wolfgang 
Published: April 2014

AbstractGlas wird oft lastabtragend eingesetzt, wobei aus Gründen der Sicherheit und des Tragverhaltens Laminate zum Einsatz kommen. Insbesondere kalt gebogene, durch Lamination formstabilisierte Gläser sind ein zunehmend nachgefragtes Produkt. Herstellungsprozess und Nutzung führen in solchen Laminaten zu teils unbekannten Spannungen, welche die Aufnahme äußerer Einwirkungen begrenzen. Optische Messverfahren mit polarisiertem Licht erlauben keine Erfassung dieser Spannungen. Dünne, innen auf die Gläser geklebte faseroptische Sensoren stellen eine mögliche Lösung dar: In Versuchen an kalt gebogenen Gläsern wird gezeigt, dass optische Sensorik dem Laminationsprozess standhält und sich für kontinuierliche Dehnungsmessungen in Glaslaminaten eignet.Fibre Optical Sensors for Strain Measurement in Cold Bent Glass Laminates. Many glass products, e.g. for structural application, are conceived as laminates for safety and load bearing behaviour reasons. Cold bent glass with shape preservation by lamination is another, increasingly popular technique. Due to manufacturing and application, such laminates can be subjected to unknown, varying interior stresses limiting the additional load bearing capacity. Optical measurement based on polarised light does not permit to determine these stresses. Thin, barely visible fibre optical sensors, glued to the interior glass surfaces, are a possible solution. RDas Bauwesen ist generell gegenüber tragenden Verklebungen skeptisch. Die Gründe sind u.a. die Größe der Bauteile und der zu übertragenden Lasten sowie die Anforderungen an Langzeitverhalten und an Auswechselbarkeit. In den letzten Jahren wurde intensiv im Bereich Holz‐Koppelrahmen geforscht und versucht an die ETAG 002 [1] angelehnte Qualitätskriterien und Bemessungsverfahren zu entwickeln. So können nach den heutigen Stand der Technik mit Glas verklebte Holz‐Koppelleisten ökonomisch und ökologisch mit metallischen Profilen konkurrieren. Die bisherigen Lösungen für kleine Bauten weiterzuentwickeln und auf mehrgeschossige aussteifende Fassadenteile zu übertragen, ist das Thema mehrerer Forschungsarbeiten und Pilotprojekte, welche in diesem Aufsatz behandelt werden.Stiffening timber‐glass façades ‐ Stiffening systems and design procedure. The structural sealant glazing is largely used in the automobile industry; the building sector is more reluctant mainly because of the long‐term behavior and the stresses due to different thermic elongations of glass and metal profiles. Materials with comparable thermic elongations to glass as wood‐based profiles are not already included in the relevant Technical guideline ETAG 002 [1]. Nevertheless, there exist considerable bonding experience in the field of windows and structural applications. During the last years, different types of wood‐based coupling frames had been developed and tested. The quality criteria and design rules based on the ETAG 002 had been proposed. This paper reports on several new research and pilot projects using new developed timber‐glass facades.
Innovative Glaskonstruktionen im historischen Kontext, Schloss Grimma
Authors: Voit Katharina , Tückmantel Peter , Nicklisch Felix , Kahlert Wolfgang 
Published: April 2014

AbstractIm Zuge des Umbaus und der Sanierung des Schlosses Grimma wurde ein gleichermaßen architektonisch sowie bautechnisch innovatives Konzept umgesetzt. Mit dem Ziel, das denkmalgeschützte Ensemble erlebbar zu machen, wurden drei neue Baukörper als filigrane Ganzglaskonstruktionen in die historische Schlossanlage eingefügt: ein gläserner Treppenturm, Eingangsbereich und Verbindungsgang. Das Herzstück des Gebäudekomplexes – der lichtdurchflutete Eingangsbereich – verknüpft die historischen Gebäude Kornhaus, Kornhausanbau und Schloss durch den gläsernen Verbindungsgang. Heute treffen moderne Ergänzungsbauten als innovative Glaskonstruktionen auf historische Gebäudeteile.Historic Castle meets modern glass construction. The castle of the German city Grimma, one of the most secular monuments in the heart of the Free State of Saxony, was restored and redeveloped. In the course of the reconstruction of the castle complex, an architectural as well as constructional innovative concept was implemented. Three additional glass buildings were integrated in order to revive this landmark: a new stair tower, foyer and walkway. Not only façade and roof show the central design idea of transparency, but also the supporting framework. The light‐flooded foyer represents the centerpiece, and connects the historical buildings. Thus, innovative glazed structure meets historical buildings today.
Analysis of epistemic uncertainty for the friction‐induced vibration
Authors: Hanselowski A. , Hanss M. 
Published: April 2014

AbstractThe phenomenon of brake squeal, which is a type of friction‐induced vibration, is analyzed using a pin‐on‐disc system. For this purpose, a finite element model is derived and its parameters are updated on the basis of experiments. The FEM analysis includes the complex eigenvalue analysis and the transient analysis. As the brake‐squeal phenomenon is very sensitive with respect to parametric uncertainty, the two numerical analyses are combined with an uncertainty analysis, which in this study is based on fuzzy arithmetic. The uncertainty analysis enables the determination of both the overall uncertainty of the considered output quantity and the influence of each individual uncertain model parameter on the overall uncertainty of the output. With this information about propagation and influence of parametric uncertainty in the system, the methods of complex eigenvalue analysis and transient analysis can be compared with respect to their appropriateness for predicting the tendency of the brake to squeal.
Characteristics of air entrainment during dynamic wetting failure along a planar substrate
Authors: Vandre E. , Carvalho M. S. , Kumar S. 
Published: April 2014

AbstractCharacteristic substrate speeds and meniscus shapes associated with the onset of air entrainment are studied during dynamic wetting failure along a planar substrate. Using high-speed video, the behaviour of the dynamic contact line (DCL) is recorded as a tape substrate is drawn through a bath of a glycerol/water solution. Air entrainment is identified by triangular air films that elongate from the DCL above some critical substrate speed. Meniscus confinement within a narrow gap between the substrate and a stationary plate is shown to delay air entrainment to higher speeds for a wide range of liquid viscosities, expanding upon the findings of Vandre, Carvalho & Kumar (J. Fluid Mech., vol. 707, 2012, pp. 496–520). A pressurized liquid reservoir controls the meniscus position within the confinement gap. It is found that liquid pressurization further postpones air entrainment when the meniscus is located near a sharp corner along the stationary plate. Meniscus shapes recorded near the DCL demonstrate that operating conditions influence the size of entrained air films, with smaller films appearing in the more viscous solutions. Regardless of size, air films become unstable to thickness perturbations and ultimately rupture, leading to the entrainment of air bubbles. Recorded critical speeds and air-film sizes compare well to predictions from a hydrodynamic model for dynamic wetting failure, suggesting that strong air stresses near the DCL trigger the onset of air entrainment.
Turbulent flow over superhydrophobic surfaces with streamwise grooves
Authors: Türk S. , Daschiel G. , Stroh A. , Hasegawa Y. , Frohnapfel B. 
Published: April 2014

AbstractWe investigate the effects of superhydrophobic surfaces (SHS) carrying streamwise grooves on the flow dynamics and the resultant drag reduction in a fully developed turbulent channel flow. The SHS is modelled as a flat boundary with alternating no-slip and free-slip conditions, and a series of direct numerical simulations is performed with systematically changing the spanwise periodicity of the streamwise grooves. In all computations, a constant pressure gradient condition is employed, so that the drag reduction effect is manifested by an increase of the bulk mean velocity. To capture the flow properties that are induced by the non-homogeneous boundary conditions the instantaneous turbulent flow is decomposed into the spatial-mean, coherent and random components. It is observed that the alternating no-slip and free-slip boundary conditions lead to the generation of Prandtl’s second kind of secondary flow characterized by coherent streamwise vortices. A mathematical relationship between the bulk mean velocity and different dynamical contributions, i.e. the effective slip length and additional turbulent losses over slip surfaces, reveals that the increase of the bulk mean velocity is mainly governed by the effective slip length. For a small spanwise periodicity of the streamwise grooves, the effective slip length in a turbulent flow agrees well with the analytical solution for laminar flows. Once the spanwise width of the free-slip area becomes larger than approximately 20 wall units, however, the effective slip length is significantly reduced from the laminar value due to the mixing caused by the underlying turbulence and secondary flow. Based on these results, we develop a simple model that allows estimating the gain due to a SHS in turbulent flows at practically high Reynolds numbers.
Gender Equality in the Ivory Tower, and How Best to Achieve It
Authors: Monroe Kristen Renwick , Choi Jenny , Howell Emily , Lampros-Monroe Chloe , Trejo Crystal , Perez Valentina 
Published: April 2014

ABSTRACTBoth statistical and qualitative interview data confirm the on-going existence of gender inequality within American academia, with women both underrepresented and underpaid compared to their male counterparts. Surprisingly, what is needed to remedy this situation is not a secret. Most of the policies outlined in this article as good workable solutions are programs that have been tested and described in more than one study. Indeed, evidence suggests that when the nine strategies we identify here are fully implemented, as they have been at a few colleges and universities, the number of women on the faculty increases dramatically. The fact that we do not adopt these policies more widely in academia suggests not a lack of knowledge so much as apathy, prejudice, gender stereotypes, and cultural cues that end by depriving society of some of its best talent and energy.
Encountering Resistance: Qualitative Insights from the Quantitative Sampling of Ex-Combatants in Timor-Leste
Authors: Roll Kate 
Published: April 2014

ABSTRACTThis article highlights the contribution of randomized, quantitative sampling techniques to answeringqualitativequestions posed by the study. In short it asks: what qualitative insights do we derive from quantitative sampling processes? Rather than simply being a means to an end, I argue the sampling process itself generated data. More specifically, seeking out more than 220 geographically dispersed individuals, selected though a randomized cluster sample, resulted in the identification of relationship patterns, highlighted extant resistance-era hierarchies and patronage networks, as well as necessitated deeper, critical engagement with the sampling framework. While this discussion is focused on the study of former resistance members in Timor-Leste, these methodological insights are broadly relevant to researchers using mixed methods to study former combatants or other networked social movements.
Excitation mechanism and thermal emission quenching of Tb ions in silicon rich silicon oxide thin films grown by plasma-enhanced chemical vapour deposition—Do we need silicon nanoclusters?
Authors: Podhorodecki A. , Golacki L. W. , Zatryb G. , Misiewicz J. , Wang J. , Jadwisienczak W. , Fedus K. , Wojcik J. , Wilson P. R. J. , Mascher P. 
Published: April 2014

In this work, we will discuss the excitation and emission properties of Tb ions in a Silicon Rich Silicon Oxide (SRSO) matrix obtained at different technological conditions. By means of electron cyclotron resonance plasma-enhanced chemical vapour deposition, undoped and doped SRSO films have been obtained with different Si content (33, 35, 39, 50 at. %) and were annealed at different temperatures (600, 900, 1100 °C). The samples were characterized optically and structurally using photoluminescence (PL), PL excitation, time resolved PL, absorption, cathodoluminescence, temperature dependent PL, Rutherford backscattering spectrometry, Fourier transform infrared spectroscopy and positron annihilation lifetime spectroscopy. Based on the obtained results, we discuss how the matrix modifications influence excitation and emission properties of Tb ions.