bluuebunny/crossref_metadata_2025 huggingface dataset:
An expedient approach to enhance Mizoroki–Heck coupling reaction by infrared irradiation using palladacycle compounds
Authors: Ortega‐Jiménez Fernando , Domínguez‐Villa Francisco X. , Rosas‐Sánchez Alfredo , Penieres‐Carrillo Guillermo , López‐Cortés José G. , Ortega‐Alfaro M. Carmen
Published: June 2015

An alternative and environmentally friendly strategy to promote the Mizoroki–Heck cross‐coupling reaction by the use of infrared irradiation using palladacycles as precatalysts is reported. Coupling products are obtained in high yield and short reaction time. A comparison with the classical use of reflux conditions, and commercial sources of palladium complexes, shows the advantages of this new alternative for promoting coupling reactions. Copyright © 2015 John Wiley & Sons, Ltd.
Schiff base‐functionalized boehmite nanoparticle‐supported molybdenum and vanadium complexes: efficient catalysts for the epoxidation of alkenes
Authors: Mirzaee Mahdi , Bahramian Bahram , Amoli Adonis
Published: June 2015

Boehmite nanoparticles, with high surface area and high degree of surface hydroxyl groups, were prepared via hydrothermal‐assisted sol–gel processing of aluminium 2‐butoxide. The produced powder was covalently functionalized with 3‐(trimethoxysilyl)propylamine, and then, in order to support vanadium oxosulfate and molybdenum hexacarbonyl complexes, all the terminal amine groups were changed to Schiff bases by refluxing with salicylaldehyde. These catalysts were applied in the epoxidation of cis‐cyclooctene and other olefins with tert‐BuOOH in CCl4. The catalytic procedures for both catalysts were optimized for various parameters such as solvent and oxidant. Recycling experiments revealed that these heterogeneous nano‐catalysts could be repeatedly applied for the epoxidation of alkenes. Copyright © 2015 John Wiley & Sons, Ltd.
Research dynamics, impact, and dissemination: A topic‐level analysis
Authors: Yan Erjia
Published: June 2015

In informetrics, journals have been used as a standard unit to analyze research impact, productivity, and scholarship. The increasing practice of interdisciplinary research challenges the effectiveness of journal‐based assessments. The aim of this article is to highlight topics as a valuable unit of analysis. A set of topic‐based approaches is applied to a data set on library and information science publications. Results show that topic‐based approaches are capable of revealing the research dynamics, impact, and dissemination of the selected data set. The article also identifies a nonsignificant relationship between topic popularity and impact and argues for the need to use both variables in describing topic characteristics. Additionally, a flow map illustrates critical topic‐level knowledge dissemination channels.
Threshold effects of the patent H‐index in the relationship between patent citations and market value
Authors: Chang Ke‐Chiun , Zhou Wei , Zhang Sifei , Yuan Chien‐Chung
Published: June 2015

This study employs a panel threshold regression model to test whether the patent h–index has a threshold effect on the relationship between patent citations and market value in the pharmaceutical industry. It aims to bridge the gap in extant research on this topic. This study demonstrates that the patent h–index has a triple threshold effect on the relationship between patent citations and market value. When the patent h–index is less than or equal to the lowest threshold, 4, there is a positive relationship between patent citations and market value. This study indicates that the first regime (where the patent h–index is less than or equal to 4) is optimal, because this is where the extent of the positive relationship between patent citations and market value is the greatest.
Personal information concerns and provision in social network sites: Interplay between secure preservation and true presentation
Authors: Min Jinyoung
Published: June 2015

Encouraging users of social network sites (SNS) to actively provide personal information is vital if SNS are to prosper, but privacy concerns have hindered users from giving such information. Previous research dealing with privacy concerns has studied mostly worries about information misuse, focusing on the protection aspects of privacy. By adopting an interpersonal conception of privacy and communication privacy management theory, this study offers a new way of understanding privacy concerns by examining the social and presentational aspects of privacy. It examines privacy concerns in terms not only of others' misuse but of others' misunderstanding and personal information in terms not only of identity but of self‐presentational information. Furthermore, it investigates the ways in which information and social risks inherent in SNS influence privacy concerns. A structural equation modeling analysis of a cross‐sectional survey of 396 Facebook users finds that longer usage does not alleviate the impact of information risk on either concern, that a greater proportion of offline friends among one's SNS friends aggravates the impact of social risk on both concerns, and that concerns about information misuse affect the provision only of identity information, whereas concerns about information misunderstanding affect the provision of both identity and self‐presentational information.
Understanding “influence”: An empirical test of theData‐FrameTheory ofSensemaking
Authors: Pontis Sheila , Blandford Ann
Published: June 2015

This paper reports findings from a study designed to gain broader understanding of sensemaking activities using theData/FrameTheory as the analytical framework. Although this theory is one of the dominant models of sensemaking, it has not been extensively tested with a range of sensemaking tasks. The tasks discussed here focused on making sense of structures rather than processes or narratives. Eleven researchers were asked to construct understanding of how a scientific community in a particular domain is organized (e.g., people, relationships, contributions, factors) by exploring the concept of “influence” in academia. This topic was chosen because, although researchers frequently handle this type of task, it is unlikely that they have explicitly sought this type of information. We conducted a think‐aloud study and semistructured interviews with junior and senior researchers from the human–computer interaction (HCI) domain, asking them to identify current leaders and rising stars in bothHCIand chemistry. Data were coded and analyzed using theData/FrameModel to both test and extend the model. Three themes emerged from the analysis: novices and experts' sensemaking activity chains, constructing frames through indicators, and characteristics of structure tasks. We propose extensions to theData/FrameModel to accommodate structure sensemaking.
A content analysis of Twitter hyperlinks and their application in web resource indexing
Authors: Yi Kwan , Choi Namjoo , Kim Yung Soo
Published: June 2015

Twitter has emerged as a popular source of sharing and delivering news information. In tweet messages, URLs to web resources and hashtags are often included. This study investigates the potential of the hyperlinks and hashtags as topical clues and indicators to tweet messages. For this study, we crawled and analyzed about 1.5 million tweets for a 3‐month period covering any topic or subject. The findings of this study revealed a power law relationship for the ranking and frequency of (a) the host names of URLs, and (b) a pair of hashtags and URLs that appeared in the tweet messages. This study also discovered that the most popular URLs used in tweets come from news and media websites, and a majority of the hyperlinked resources are news web pages. One implication of this study is that Twitter users are becoming more active in sharing already published information than producing new information. Finally, our investigation on hashtags for web resource indexing reveals that hashtags have the potential to be used as indexing terms for co‐occurring URLs in the same tweet. We also discuss the implications of this study for web resource recommendation.
Using path‐based approaches to examine the dynamic structure of discipline‐level citation networks: 1997–2011
Authors: Yan Erjia , Yu Qi
Published: June 2015

The objective of this paper is to identify the dynamic structure of several time‐dependent, discipline‐level citation networks through a path‐based method. A network data set is prepared that comprises 27 subjects and their citations aggregated from more than 27,000 journals and proceedings indexed in the Scopus database. A maximum spanning tree method is employed to extract paths in the weighted, directed, and cyclic networks. This paper finds that subjects such as Medicine, Biochemistry, Chemistry, Materials Science, Physics, and Social Sciences are the ones with multiple branches in the spanning tree. This paper also finds that most paths connect science, technology, engineering, and mathematics (STEM) fields; 2 critical paths connecting STEM and non‐STEM fields are the one from Mathematics to Decision Sciences and the one from Medicine to Social Sciences.
Analyzing data citation practices using the data citation index
Authors: Robinson‐García Nicolas , Jiménez‐Contreras Evaristo , Torres‐Salinas Daniel
Published: June 2015

We present an analysis of data citation practices based on the Data Citation Index (DCI) (Thomson Reuters). This database launched in 2012 links data sets and data studies with citations received from the other citation indexes. The DCI harvests citations to research data from papers indexed in the Web of Science. It relies on the information provided by the data repository. The findings of this study show that data citation practices are far from common in most research fields. Some differences have been reported on the way researchers cite data: Although in the areas of science and engineering & technology data sets were the most cited, in the social sciences and arts & humanities data studies play a greater role. A total of 88.1% of the records have received no citation, but some repositories show very low uncitedness rates. Although data citation practices are rare in most fields, they have expanded in disciplines such as crystallography and genomics. We conclude by emphasizing the role that the DCI could play in encouraging the consistent, standardized citation of research data—a role that would enhance their value as a means of following the research process from data collection to publication.
Scientific research measures
Authors: Frittelli Marco , Mancini Loriano , Peri Ilaria
Published: June 2015

The evaluation of scientific research is crucial for both the academic community and society as a whole. Numerous bibliometric indices have been proposed for the ranking of research performance, mainly on an ad hoc basis. We introduce the novel class of Scientific Research Measures (SRMs) to rank scientists' research performance and provide a rigorous theoretical foundation for these measures. In contrast to many bibliometric indices, SRMs take into account the whole citation curve of the scientist, offer appealing structural properties, allow a finer ranking of scientists, correspond to specific features of different disciplines, research areas and seniorities, and include several bibliometric indices as special cases. Thus SRMs result in more accurate rankings than ad hoc bibliometric indices. We also introduce the further general class of Dual SRMs that reflect the “value” of journals and permit the ranking of research institutions based on theoretically sound criteria, which has been a central theme in the scientific community over recent decades. An empirical application to the citation curves of 173 finance scholars shows that SRMs can be easily calibrated to actual citation curves and generate different authors' rankings than those produced by seven traditional bibliometric indices.
Information inequality in contemporary Chinese urban society: The results of a cluster analysis
Authors: Yu Liangzhi , Zhou Wenjie
Published: June 2015

Having reflected on the theoretical tradition of previous information inequality research that treats society's information rich/poor as identical with its socioeconomic rich/poor, this study examines the informational structure of contemporary Chinese urban society through a cluster analysis of a sample of 3,361 urban residents measured by a holistic informational measurement developed around the concept of “an individual's information world.” It finds that, first, 4 groups, instead of a binary “haves versus have‐nots,” best characterize Chinese urban society informationally; second, the distribution of people among these groups conforms to normal distribution, in striking contrast with the pyramid‐shaped socioeconomic structure of Chinese society; third, although the demographic characteristics of these groups suggest a significant correlation between people's informational and socioeconomic statuses, the 2 are far from identical; fourth, although the 4 groups differ in all aspects investigated, they differ most notably in information assets and the range and type of materials they choose as their regular information resources; fifth, although the 4 groups vary significantly, each differs from the others in its own way. This study concludes that society's informational and socioeconomic structures are 2 related but distinctive structures, and that the informational structure is characterized by highly complicated textures of inequality.
Nobel numbers: Time‐dependent centrality measures on coauthorship graphs
Authors: Fields Chris
Published: June 2015

A time‐dependent centrality metric for disciplinary coauthorship graphs, the “Nobel number” for a discipline, is introduced. A researcher's Nobel number for a given discipline in a given year is defined as the researcher's average coauthorship distance to that discipline's Nobel laureates in that year. Plotting Nobel numbers over several decades provides a quantitative as well as visual indication of a researcher's proximity to the intuitive “center” of a discipline as defined by recognized scientific achievement. It is shown that the Nobel number distributions for physics of several researchers both within and outside of physics are surprisingly flat over the five‐decade span from 1951 to 2000. A model in which Nobel laureates are typically connected by short coauthorship paths both intergenerationally and between subdisciplines reproduces such flat Nobel number distributions.
Booklovers' world: An examination of factors affecting continued usage of social cataloging sites
Authors: Choi Namjoo , Joo Soohyung
Published: June 2015

Little is known about what factors influence users' continued use of social cataloging sites. This study therefore examines the impacts of key factors from theories of information systems (IS) success and sense of community (SOC) on users' continuance intention in the social cataloging context. Data collected from an online survey of 323 social cataloging users provide empirical support for the research model. The findings indicate that both information quality (IQ) and system quality (SQ) are significant predictors of satisfaction and SOC, which in turn lead to users' intentions to continue using these sites. In addition, SOC was found to affect continuance intention not only directly, but also indirectly through satisfaction. Theoretically, this study draws attention to a largely unexplored but essential area of research in the social cataloging literature and provides a fundamental basis to understand the determinants of continued social cataloging usage. From a managerial perspective, the findings suggest that social cataloging service providers should constantly focus their efforts on the quality control of their contents and system, and the enhancement of SOC among their users.
Highly cited papers in Library and Information Science (LIS): Authors, institutions, and network structures
Authors: Bauer Johann , Leydesdorff Loet , Bornmann Lutz
Published: June 2015

As a follow‐up to the highly cited authors list published by Thomson Reuters in June 2014, we analyzed the top 1% most frequently cited papers published between 2002 and 2012 included in the Web of Science (WoS) subject category “Information Science & Library Science.” In all, 798 authors contributed to 305 top 1% publications; these authors were employed at 275 institutions. The authors at Harvard University contributed the largest number of papers, when the addresses are whole‐number counted. However, Leiden University leads the ranking if fractional counting is used. Twenty‐three of the 798 authors were also listed as most highly cited authors by Thomson Reuters in June 2014 (http://highlycited.com/). Twelve of these 23 authors were involved in publishing 4 or more of the 305 papers under study. Analysis of coauthorship relations among the 798 highly cited scientists shows that coauthorships are based on common interests in a specific topic. Three topics were important between 2002 and 2012: (a) collection and exploitation of information in clinical practices; (b) use of the Internet in public communication and commerce; and (c) scientometrics.
H∞ Control with Transients for Singular Systems
Authors: Feng Zhiguang , Lam James , Xu Shengyuan , Zhou Shaosheng
Published: June 2015

In this paper, the problem of a generalized type of H∞ control is investigated for continuous‐time singular systems, which treats a mixed attenuation of exogenous inputs and initial conditions. First, a performance measure that is essentially the worst‐case norm of the regulated outputs over all exogenous inputs and initial conditions is introduced. A necessary and sufficient condition is obtained to ensure the singular system to be admissible and the performance measure to be less than a prescribed scalar. Based on the criterion a sufficient condition for the existence of a state‐feedback controller is established in terms of linear matrix inequalities. Moreover, the relationship between the performance measure and the standard H∞ norm of the system is provided. Two numerical examples are given to demonstrate the properties of the obtained results.
Robust State‐and‐Disturbance Observer Design for Linear Non‐minimum‐phase Systems
Authors: Chen Min‐Shin , Lin Shih‐Yu , Tseng Ming‐Lei , Yeh Yi‐Liang , Yen Jia‐Yush
Published: June 2015

When there are external disturbances acting on the system, the conventional Luenberger observer design for state estimation usually results in a biased state estimate. This paper presents a robust state and disturbance observer design that gives both accurate state and disturbance estimates in the face of large disturbances. The proposed robust observer is structurally different from the conventional one in the sense that a disturbance estimation term is included in the observer equation. With this disturbance estimation term, the robust observer design problem is skillfully transformed into a disturbance rejection control problem. We then can utilize the standard H∞ control design tools to optimize the robust observer between the disturbance rejection ability and noise immune ability. An important advantage of the proposed robust observer is that it applies to both minimum‐phase systems and non‐minimum phase systems.
Modeling distributions of travel time variability for bus operations
Authors: Ma Zhenliang , Ferreira Luis , Mesbah Mahmoud , Zhu Sicong
Published: June 2015

Bus travel time reliability performance influences service attractiveness, operating costs, and system efficiency. Better understanding of the distribution of travel time variability is a prerequisite for reliability analysis. A wide array of empirical studies has been conducted to model distribution of travel times in transport. However, depending on the data tested and approaches applied to examine the fitting performance, different conclusions have been reported. This paper aims to specify the most appropriate distribution model for the day‐to‐day travel time variability by using a novel evaluation approach and set of performance measures. Two important issues are explored using automatic vehicle location data collected on two typical bus routes over 6 months in Brisbane, namely, data aggregation influences on travel time distribution and comprehensive evaluation of performance of distribution models. The decrease of temporal aggregation of travel times tends to increase the normality of distributions. The spatial aggregation of link travel times would break up the link multimodality distributions for a busway route, but unlike for a non‐busway route. The Gaussian mixture models are evaluated as superior to its alternatives in terms of fitting accuracy, robustness, and explanatory power. The reported distribution model shows promise to fit travel times for other services with different operation environments considering its flexibility in fitting symmetric, asymmetric, and multimodal distributions. The improved statistic fitting can support more effective service reliability analysis. Copyright © 2015 John Wiley & Sons, Ltd.
Tragfähigkeit und Verformungsverhalten von Kammverbindungen
Authors: Meisel Andreas , Wallner Bernhard , Schickhofer Gerhard
Published: June 2015

Kämme für Kreuz‐ und Eckverbindungen sind wesentliche Bestandteile nahezu jedes zimmermannsmäßig errichteten Holztragwerks in Mitteleuropa. Die Anwendung dieser Verbindungen als statisch tragende Anschlüsse nach EN 1995‐1‐1 bedarf der Kenntnis der mechanischen Kenngrößen. Umso erstaunlicher ist es, dass in der Literatur bislang Angaben zur Tragfähigkeit und insbesondere zum Verformungsverhalten fehlen.

In diesem Beitrag werden 26 zerstörende Prüfungen an unterschiedlichen Kammverbindungen und deren Auswertungen vorgestellt. Sowohl für die Bemessung dieser Verbindungen als auch für die Ermittlung der Steifigkeiten – abgeleitet aus dem Verformungsverhalten – werden Berechnungsvorschläge angegeben.

Load‐bearing capacity and load‐bearing behaviour of notched joints

Cross and corner joints using notches are important members of almost every roof structure erected by carpenters in central europe. The structural usage of these joints demands the knowledge of their load‐bearing capacity and behaviour according to EN 1995‐1‐1. It's even more astonishing, that therefore codes and literature lack information.

This contribution deals with 26 tests of different notched joints and their results. Both proposals for the design and for the determination of the stiffnesses of these joints are given here.
Frühgeschichte des modernen Konstruktionsbetons
Authors: Veihelmann Karen
Published: June 2015

Nachdem in den vorangegangenen beiden Teilen des Aufsatzes zur Frühgeschichte des Betons, dessen erste Anwendungen im Molen‐ und Schleusenbau dargelegt wurden, beschreibt der nun vorliegende dritte Teil die Entwicklungen im Hochbau. Ausgehend vom Stampflehmbau (Pisé) erfuhr die Bauweise mittels Ersetzen des Bindemittels Lehm zunächst durch reinen, später durch hydraulischen Kalk sowie die verschiedenen Spielarten von Zement bedeutende Fortschritte: Aus Stampflehm wurde auf diese Weise Stampfbeton. Die Verbesserung sowohl der Witterungsbeständigkeit als auch der Druckfestigkeit schuf die Grundlage für den breitgefächerten Einsatz von Beton im Hochbau. War zunächst noch die nicht kalkulierbare Qualität des Portlandzementes dem Aufschwung des Betonbaus hinderlich, bedeutete die Einführung der ersten deutschen Zementnormen im Königreich Preußen 1878 den Durchbruch für den Beton im Hochbau, insbesondere aber als Konstruktionsmaterial für weitgespannte Brücken.

On the early history of modern concrete – part III: From rammed earth to rammed concrete

Following the first two parts of the paper on early history of modern concrete which dealt with underwater concrete structures the present part III analyses the development of concrete above ground. Based on the experience of building with rammed earth the technique was improved by replacing the binder clay by lime, later by cement: thus rammed earth became rammed concrete. This improvement of weather resistance and compressive strength opened a wide field of application of concrete above ground. In Germany, the unforeseeable quality of cement first delayed the implementation of concrete structures. It was only in 1878 when the first cement standards were introduced. From that point concrete was used for all kinds of structures, particularly for wide span bridges.
Biegeaktive Tragwerke
Authors: Lienhard Julian , Knippers Jan
Published: June 2015

Biegeaktive Tragwerke sind gekrümmte Tragwerke, deren Geometrie und Systemsteifigkeit sich aus einer elastischen Verformung von Tragelementen ergibt. Biegung kann demnach dazu genutzt werden, komplexe räumlich gekrümmte Tragsysteme aus ursprünglich geradlinigen oder ebenen Tragelementen zu erzeugen. Bei der Arbeit mit biegeaktiven Tragstrukturen zeigt sich, dass dieser Formgebungsansatz die Entwicklung hocheffizienter Tragsysteme ermöglicht, welche – frei von tradierten typologischen Ansätzen der Tragwerkslehre – aus dem Kurzschließen von Rückstellkräften entstehen. Nach einer Definition der Begriffe und kurzen Darstellung der relevanten mechanischen sowie werkstofftechnischen Grundlagen werden in diesem Aufsatz die besonderen Eigenschaften dieser Tragwerke anhand von Fallbeispielen erläutert.

Bending‐active structures

Bending‐active structures are curved beam or surface structures that base their geometry and structural integrety on the elastic deformation of their initially straight or planar elements. In these lightweight structures bending is not avoided but instrumentalized to create complex curved geometries on the basis of standard semi‐finished building products. After a general introduction of material and mechanical basics this paper discusses the behavior of bending‐active structures through three case study projects.
Stand der Wissenschaft zum Brandschutz im mehrgeschossigen Holzbau
Authors: Kampmeier Björn , Winter Stefan
Published: June 2015

Mit der Muster‐Holzbaurichtlinie 2004 (M‐HFHHolzR) wurde die Möglichkeit geschaffen, Gebäude in Holz bis zu einer Höhe des obersten Geschossfußbodens von 13 m in Holz zu errichten. Die Richtlinie ist in den meisten Bundesländern zwischenzeitlich bauaufsichtlich eingeführt. In der Richtlinie wird allerdings gefordert, dass die hölzernen Tragglieder mit einer nicht brennbaren Bekleidung geschützt werden, die mindestens 60 Minuten lang eine Entzündung des Holzes verhindert. Die Richtlinie beschränkt sich zudem auf die Holztafelbauweise, bei der die Hohlräume vollständig mit nicht brennbarer Wärmedämmung gefüllt sein müssen sowie auf Brettstapeldecken. An der Fassade ist der Einsatz von Holz durch die bauaufsichtliche Anforderung “schwer entflammbar” ohne begründete Abweichung nicht möglich.

Die in den letzten Jahren errichteten mehrgeschossigen Holzbauten weisen häufig erhebliche Abweichungen von diesen Anforderungen auf. Zudem zeigte sich in der baulichen Umsetzung, dass vor allen Dingen die Führung von Installationen und die Ausbildung von Bauteilanschlüssen zu Problemen führten.

In dieser Veröffentlichung werden die wesentlichen Untersuchungen zu diesem Themenfeld aus den letzten Jahren zusammengefasst und Hinweise auf weiterführende Literatur gegeben. Dies betrifft die Optimierung und Reduzierung der Brandschutzbekleidung, die Verwendung brennbarer Dämmstoffe und massiver Holzbauelemente, die Führung von Installationen und die Ausbildung von Bauteilanschlüssen.

State of the art in fire protection of multi‐storey timber buildings

With introducing the model guideline for fire protective requirements on multi‐storey buildings made of timber in the year 2004 it became possible to construct buildings out of timber up to a height of the upper floor of 13 m. For these types of houses the building code requires a non‐combustible cladding to prevent the load bearing timber structure from ignition over 60 minutes time. Furthermore, combustible insulation materials are not allowed inside the timber frame construction.

Multi‐storey timber buildings built in the last few years often had significant differences to these regulations. Real building projects show that especially service installations and the joints between building elements cause problems in praxis.

The results of the main research projects in this topic are summarized in this paper and references to further reading are given concerning to optimization of the non‐ combustible cladding, application of combustible insulation and solid timber constructions, integration of service installations and the jointing of different elements.
Multi‐criteria assessment of yellow, green, and woody biomasses: pre‐screening of potential biomasses as feedstocks for biorefineries
Authors: Parajuli Ranjan , Knudsen Marie Trydeman , Dalgaard Tommy
Published: June 2015

The need for sustainable production of food, feed, and fuel for a growing global population with minimum pressure on land use and other ecological impacts is a major challenge. The aim of the current study is to pre‐screen available biomass types to prepare for a system‐wide sustainability assessment in related biorefinery value chains. The study describes the use of multiple‐criteria decision‐making techniques as tools for assessing criteria and to draw preferences among the alternatives. Thirteen biomass types (classified as yellow, green, and woody) are evaluated with respect to 15 criteria. The criteria are classified under the three assessment parameters: supply potential, biomass properties, and potential environmental gain/losses. Pair‐wise comparisons of the alternatives are carried out in an outranking method (PROMETHEE) on the basis of their ratings (on a 1–5 scale) and weights assigned to the criteria. Weighting factors of the criteria are calculated by using the Analytical Hierarchy Process (AHP). The study shows that the net outranking flow for the most preferred biomass types are: grass‐clover 2.8, wheat‐straw 1.2 and willow 1, representing the biomass categories green, yellow and woody, respectively. The overall order of the preferred biomass types is grass‐clover, pure grass, alfalfa from the green category; straw based on wheat and barley from the yellow category; and willow from the woody category. Furthermore, irrespective of whether or not the raw materials are processed in integrated biorefineries, preferences on biomass types are also important in the context of their sustainable conversions in related biorefinery platforms (e.g. straw in a sugar‐based lignocellulosic biorefinery and grass‐clover in a green biorefinery). © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd
Ermüdung von Verbundkonstruktionen mit Verbunddübelleisten (lokales Tragverhalten)
Authors: Gallwoszus Joerg , Claßen Martin , Hartje Jens
Published: June 2015

Im modernen Brückenbau werden insbesondere für den Bereich kleiner und mittlerer Spannweiten immer häufiger Stahl‐Beton‐Verbundkonstruktionen mit Verbunddübelleisten eingesetzt. Im Gegensatz zu Kopfbolzendübeln, bei denen bereits nach wenigen Lastwechseln Anrisse im Stahl entstehen, ist die Lebensdauer von Verbunddübelleisten größtenteils durch die Verdichtung des mehraxial beanspruchten Betons in den Dübelausnehmungen geprägt. Hier treten plastische Betonstauchungen auf, die sich über die Lastspiele akkumulieren und zu einer zyklischen Zunahme der Relativverschiebungen in der Verbundfuge führen. Teile dieser Relativverschiebungen verbleiben auch bei Entlastung und werden als inelastischer Schlupf bezeichnet. Der anfänglich starre Verbund zwischen Stahl und Beton geht mit zunehmender Lastwechselspielzahl in einen nachgiebigen Verbund über, wodurch Schnittgrößenumlagerungen zwischen den Verbundpartnern auftreten, die in den Ermüdungsnachweisen des Stahlträgers zu berücksichtigen sind. Im vorliegenden Beitrag werden zyklische Abscherversuche zur Untersuchung der zyklischen Schlupfzunahme vorgestellt. Hierbei wird der Einfluss belastungsabhängiger Parameter (Oberlast und Lastschwingbreite) untersucht. Weiterhin wird ein Ingenieurmodell zur rechnerischen Berücksichtigung der zyklischen Schlupfzunahme in Ermüdungsnachweisen vorgeschlagen.

Fatigue of composite constructions with composite dowels (local behavior)

Composite dowels are innovative shear connectors with great potential to benefit the construction of steel‐concrete composite bridges with small and medium spans. Contrary to headed stud connectors, where initial steel cracks already occur after a few load cycles, the lifetime of composite dowels is predominately characterized by the compression of the multiaxial stressed concrete in front of the composite dowel, where shear forces are transferred between steel and concrete. Here, plastic concrete compression strains occur, that accumulate over the load cycles and lead to a cyclical increase of relative displacements in the composite connection. Certain proportions of these relative displacements remain constant in the connection, even after release of external loading. These permanent displacements are called inelastic slip. The initially rigid connection between steel and concrete degrades over the lifetime and rearrangements of internal forces between the composite partners occur, which may not be neglected in fatigue design. The present paper describes cyclic shear tests investigating the processes of cyclic slip increase. Here, the impacts of load‐dependent parameters (upper load level and load range) onto the inelastic slip evolution are analyzed. Furthermore an engineering model is proposed, which can be used to consider cyclic slip increase in fatigue design.
Untersuchung der Rissbreiten in textilbewehrten Betonen
Authors: Hansl Mario , Feix Jürgen
Published: June 2015

Die besondere Eignung textilbewehrter Betone zur nachträglichen Verstärkung bestehender Stahlbetonbauteile konnte bereits in zahlreichen Studien eindrucksvoll belegt werden. Bei den dabei durchgeführten Untersuchungen konnte zusätzlich zur Verstärkungswirkung häufig auch ein günstiger Einfluss der textilbewehrten Verstärkungsschicht auf das Rissverhalten der untersuchten Probekörper festgestellt werden. Textilbeton zeigt somit auch in der Funktion als schützende Schicht zur Erhöhung der Dauerhaftigkeit der bestehenden Bausubstanz großes Potenzial. Tiefgreifende Kenntnisse über den Prozess der Rissbildung und die Entwicklung der Rissbreiten im Textilbeton sind dabei für eine diesbezügliche Anwendung von besonderer Bedeutung. Der vorliegende Beitrag berichtet von experimentellen Untersuchungen zum Rissverhalten von Textilbeton unter einaxialer Zugbelastung sowie die Ableitung eines Berechnungsmodells zur direkten Berechnung der maximalen Rissbreite.

Investigation of crack width in textile reinforced concrete

Several studies have verified the suitability of textile reinforced concrete (TRC) for the strengthening of existing reinforced concrete structures. Furthermore, experiments have also shown that TRC strengthening layers have a positive impact on the crack behavior of tested specimens. This effect indicates a high potential for the use of TRC as a protection layer for increasing the durability of existing structures. In order to use TRC as a protective layer, however, a better understanding of its crack behavior and crack width development is needed. The present study reports on experimental investigations of TRC crack behavior under unidirectional stress and a theoretical model for predicting maximum crack width.
Entstehung von fleckigen Dunkelverfärbungen an Sichtbetonoberflächen im späten Alter
Authors: Strehlein Doris , Schießl Peter
Published: June 2015

Der Fokus des Beitrags richtet sich auf das Phänomen der fleckigen Dunkelverfärbungen, welche im späten Alter, d. h. Monate bis Jahre nach der Herstellung der Sichtbetonbauteile, auftreten und deren Ausmaß ohne weitere Maßnahmen zeitabhängig zunimmt. Anhand eines Praxisbeispiels wird das Phänomen beschrieben und die für die Entstehung der fleckigen Dunkelverfärbungen im späten Alter ursächlichen Mechanismen aufgezeigt. Abschließend werden baupraktische Empfehlungen zur Vermeidung der Dunkelverfärbungen im späten Alter formuliert.

Formation of mottled dark discoloration on fairfaced concrete surfaces occuring in the late age – Description of the causal mechanisms based on a practical example

The article is focused on the phenomenon of mottled dark discoloration, which occur in the late age, i.e. months to years after the production of fairfaced concrete elements. Without countermeasure the extent of the discoloration increases time‐dependent. Based on a practical example the phenomenon is described and the main mechanisms that lead to the mottled dark discoloration are shown. Finally, appropriate recommendations for preventing mottled dark discoloration in the late age are made for building practice.
Montage bei tiefen Temperaturen – Einfluss auf das Tragverhalten chemischer Dübel
Authors: Fuchs Werner , Hofmann Jan , Hülder Gerrit
Published: June 2015

In den letzten zehn Jahren wurden erhebliche Anstrengungen unternommen, um die Anwendungsgebiete von chemischen Befestigungsmitteln zu erweitern. Daher werden chemische Dübel in weiten Bereichen für Verbindungen im Stahlbetonbau eingesetzt.

Zur Gewährleistung der konstruktiven Zuverlässigkeit von chemischen Befestigungsmitteln wurden Zulassungsverfahren zur Qualifizierung, wie z. B. in Europa ETAG 001, T. 5 oder AC308 und ACI 355.4 in den USA, entwickelt. Während amerikanische Vorschriften einen Versuch fordern, der das Setzen im Winter und die darauffolgende Erwärmung an einem sonnigen Tag simuliert, befassen sich die europäischen Prüfrichtlinien nicht mit diesem Anwendungsfall.

Dieser Beitrag stellt die Ergebnisse eines Versuchsprogramms vor, das entwickelt wurde, um die Anfälligkeit von chemischen Mörteln, die für Verbunddübel verwendet werden, gegenüber einer Montage bei tiefen Temperaturen aufzuzeigen. Die Versuchsergebnisse zeigen eindeutig, dass das Verhalten unter Montagebedingungen bei tiefen Temperaturen unzureichend in den europäischen und teilweise auch in den amerikanischen Vorschriften berücksichtigt ist. Ein neuer Qualifizierungsversuch und seine Auswertung, in dem die ungünstigen Auswirkungen von tiefen Temperaturen berücksichtigt werden, wird in diesem Beitrag vorgestellt. Er ist inzwischen auch in AC308 umgesetzt.

Load bearing behavior of chemical fasteners after installation at decreased temperatures

In the last 10 years there have been made tremendous developments to increase the fields of applications of adhesive anchor systems. Hence these systems are used for structural attachments in a wide variety of applications in concrete construction.

In order to ensure the structural reliability of adhesive anchors prequalification procedures such as ETAG 001, P. 5 in Europe or AC308 and ACI 355.4 in the USA were developed. Both procedures require reliability tests to check the behavior under deep temperature installation conditions. Whereas the American provisions require a prequalification test reflecting an installation during e.g. in winter and the subsequent heating on a sunny day the European prequalification guidelines are quiet in respect to this matter.

This paper presents results of a test program developed to demonstrate the susceptibility of adhesives used for post installed chemical anchors to decreased temperatures installations. The test results clearly indicate that the behavior of decreased temperature installation is insufficiently considered in the European and partially also in American product prequalification provisions. A proposal for a new test and its evaluation to cover the unfavorable effects of decreased installation conditions is presented. In the meantime this proposal was included to AC308.
Spectroscopic and photoluminescence characterization of Dy3+ in Sr0.5Ca0.5TiO3 phosphor
Authors: Vidyadharan Viji , Sreeja E. , Jose Saritha K. , Joseph Cyriac , Unnikrishnan N. V. , Biju P. R.
Published: June 2015

The spectroscopic and photoluminescence characteristics of trivalent dysprosium (Dy3+)‐doped Sr0.5Ca0.5TiO3 phosphor materials synthesized via solid‐state reaction method were studied. The X‐ray diffraction profile confirmed the orthorhombic perovskite structure of the prepared samples. Judd–Ofelt analysis was carried out to obtain the intensity parameters and predicted radiative properties of Sr0.5Ca0.5TiO3:2wt%Dy3+. The photoluminescence spectrum of Dy3+‐doped Sr0.5Ca0.5TiO3 showed three emission peaks at 481, 574 and 638 nm corresponding to 4F9/2→6H15/2, 4F9/2→6H13/2 and 4F9/2→6H11/2 transitions respectively. The variation of luminescence intensity with different excitation wavelengths and Dy3+ concentrations is discussed. The decay profiles of 4F9/2 excited levels of Dy3+ ions show bi‐exponential behaviour and also a decrease in average lifetime with increase in Dy3+ concentration. Yellow to blue luminescence intensity ratio, CIE chromaticity co‐ordinates and correlated color temperature were also calculated for different concentrations of Dy3+‐doped Sr0.5Ca0.5TiO3 phosphor at different λex. Copyright © 2015 John Wiley & Sons, Ltd.
Brotgetreide
Authors: Bickel Susanne
Published: June 2015

Unter Brotgetreide verstehen wir heute die Weizenarten, vor allem Weichweizen und Dinkel sowie Roggen. Um Züchtungsziele schneller erreichen zu können, ist das riesige Weizengenom heute Objekt intensiver Forschung. Weizen ist hexaploid und enthält drei Genome nebeneinander, die sich nicht untereinander vermischen. Die Urformen von Einkorn (diploid) und Emmer (tetraploid) waren Vorfahren des heutigen Weizens und des Dinkels. Dinkel ist weniger anspruchsvoll als Weizen, hat aber den Nachteil, einen zusätzlichen Gerbgang zu benötigen um die Körner ohne Spelzen zu gewinnen. Er gehört heute wieder zu den modernen Brotgetreiden. Der Proteinanteil des Roggens ist ernährungsphysiologisch wertvoller als der des Weizens, da mehr essentielle Aminosäuren vorhanden sind. Roggen ist ein typisches deutsches Brotgetreide. Das resultiert zum einen daraus, dass die norddeutschen Böden für Roggen geeigneter waren als Weizen und zum anderen aus klimatischen Gründen.
Lässt sich altersbedingter Muskelschwund stoppen?
Authors: Ohlendieck Kay
Published: June 2015

Sarkopenie bezeichnet den altersassoziierten Verlust an Muskelmasse und Muskelkraft und ist charakterisiert durch eine erheblich verminderte Regenerationsfähigkeit von gealterten Muskelfasern und einer elektromechanischen Entkopplung zwischen Motornerv und Muskel. Die Anwendung der vergleichenden Proteomanalyse auf dem Gebiet der Muskelalterung hat interessante neue pathobiochemische Erkenntnisse generiert. Altersbedingte Muskelschwäche ist gekennzeichnet durch sekundäre schnell/langsam Übergänge im Myofibrillenapparat und glykolytisch/oxidative Veränderungen beim Energiestoffwechsel. Die Identifizierung neuer Proteinbiomarker der Muskelalterung bedeuten einen erheblichen Fortschritt bei der Etablierung neuer diagnostischer Methoden und therapeutischer Verfahren zur Abmilderung des Gebrechlichkeitssyndroms.
Paläoklima: Knochen weisen den Weg
Authors: Sommer Robert S.
Published: June 2015

Während der letzten Eiszeit (Weichsel) und auch im heutigen Holozän gab es eine Vielzahl von zum Teil sehr schnellen und drastischen Klimaschwankungen. Die Muster an biologischer Vielfalt, die wir sie heute beispielsweise in der nordeuropäischen Tiefebene finden, tragen eine deutliche Signatur der Vergangenheit. Mit Hilfe von verschiedenen wissenschaftlichen Methoden aus dem Bereich der Bio‐ und Geowissenschaften ist es möglich, Wechselwirkungen von Jahrtausende zurückliegenden Prozessen wie Klimaveränderungen, Ausbreitung oder Aussterben von Arten und Veränderungen der Ökosysteme zu untersuchen und zu verstehen. Dabei können die Fundmuster von subfossilen Knochenablagerungen der Arten, alte DNA oder stabile Isotope aus Knochen sehr hilfreiche Methodenbausteine sein, um die Vergangenheit zu entschlüsseln. Ein Blick in die Paläoökologie zeigt, wie es zur Zusammensetzung unserer heutigen Fauna gekommen ist und was in Zukunft passieren könnte.
Darwinfinken: Wie ihnen der Schnabel gewachsen ist
Authors: Kronberg Inge
Published: June 2015

Darwinfinken sind ein Lehrbuchbeispiel für adaptive Radiation und Artbildung. Sie zeigen, wie aus einer einzelnen Art durch Variation, Isolation und Separation neue Arten entstehen. Eine schwedische Forschergruppe sequenzierte nun das Genom von allen bekannten Arten der Darwinfinken. Sie überprüften den phylogenetischen Stammbaum und fanden ein Schlüsselgen für die Vielfalt der Schnabelformen.
Teixobactin: Reservemunition aus dem Boden
Authors: Tetsch Larissa
Published: June 2015

Lange Zeit als besiegt angesehene Infektionskrankheiten sind heute wieder auf dem Vormarsch. Ein Grund hierfür sind zunehmende Antibiotikaresistenzen, die die Entwicklung neuartiger Wirkstoffe nötig machen. Aus einem zuvor unkultivierten Bodenbakterium wurde kürzlich das Breitband‐Antibiotikum Teixobactin isoliert, das die Synthese der Zellwand grampositiver Bakterien durch Bindung an Zellwandvorstufen hemmt.
Universum Bremen: Entdecken, Begreifen und Bestaunen
Authors: Högermann Christiane
Published: June 2015

Die Beantwortung vieler Fragen aus Naturwissenschaften, Technik und Alltag, von denen man häufig noch gar nicht wusste, dass es sie und sogar eine (verblüffende) Antwort darauf gibt, hat sich das wieder eröffnete Science‐Center Universum Bremen zum Ziel gesetzt.
Metathesis of 1‐Hexene over Heterogeneous Tungsten‐Based Catalysts
Authors: Prithipal Arisha , Lokhat David , Starzak Maciej
Published: June 2015

1‐Hexene metathesis was performed over standard and potassium‐doped WO3/SiO2 catalysts. The samples were tested at various reaction temperatures, molar feed compositions, and space times. Under the applied reaction conditions, doping with potassium reduced the isomerization and cracking activity of the catalyst by at least half and improved the yield of detergent‐range alkenes twofold. However, increasing the potassium loading to a higher amount resulted in a significant reduction in the metathesis activity as both Brønsted and Lewis acid sites were affected. Optimum operating conditions for the yield of detergent‐range alkenes were identified using response surface methodology.
Integration of Fire and Explosion Index in 3D Process Plant Design Software
Authors: Mitkowski Piotr T. , Bal Sylwia K.
Published: June 2015

Process design management system is the essential computer‐aided design type of software used in design and 3D modeling of process plants. Actually, it is a management center of process plant projects which allows designers and engineers from various disciplines to concurrently create, control, and manage changes to the plant design and other related engineering data. Some methods for achieving the inherently safer designs guide the location of process equipment and utilities. Therefore, there is room for close interactions between 3D modeling and methods to assess the inherent safety. The feasibility of integration of the Fire and Explosion Index into 3D modeling of industrial chemical processes is evaluated and supported by a case study. The importance of the presented concept as key part of such management philosophies like the lean design and the building information modeling is highlighted.
Particle Motion in Two‐ and Three‐Phase Fluidized‐Bed Reactors Determined by Pulsed Field Gradient Nuclear Magnetic Resonance
Authors: Zhang Qing , Zhou Yefeng , Wang Jingdai , Jiang Binbo , Yang Yongrong , Stapf Siegfried , Mattea Carlos , Gong Qingxia
Published: June 2015

Pulsed‐field gradient nuclear magnetic resonance (PFG‐NMR) was employed to investigate the velocity distribution (propagator) and dispersion coefficient of a model fluidized‐bed reactor of low aspect ratio containing mustard seeds. Both propagator and dispersion were found to be strongly anisotropic due to slug‐flow conditions, with the vertical/axial dispersion ratio becoming smaller with increasing air flow rate. The influence of air humidity and flow rate was discussed in the gas‐solid system, and the concurrent effect of electrostatic charging of particles close to the reactor wall was shown. Dispersion was generally found to increase with growing humidity and superficial gas velocity. For comparison, results are presented for a gas‐liquid‐solid system with a water‐to‐particle mass ratio of 2:1 as a function of bed height. The results indicated that the addition of water enhanced the particle motion in the bed.