bluuebunny/crossref_metadata_2025 huggingface dataset:
TANGOS: The Agile Numerical Galaxy Organization System
Authors: Pontzen Andrew , Tremmel Michael
Published: July 2018

We present tangos, a Python framework and web interface for database-driven analysis of numerical structure formation simulations. To understand the role that such a tool can play, consider constructing a history for the absolute magnitude of each galaxy within a simulation. The magnitudes must first be calculated for all halos at all timesteps and then linked using a merger tree; folding the required information into a final analysis can entail significant effort. Tangos is a generic solution to this information organization problem, aiming to free users from the details of data management. At the querying stage, our example of gathering properties over history is reduced to a few clicks or a simple, single-line Python command. The framework is highly extensible; in particular, users are expected to define their own properties, which tangos will write into the database. A variety of parallelization options are available and the raw simulation data can be read using existing libraries such as pynbody or yt. Finally, tangos-based databases and analysis pipelines can easily be shared with collaborators or the broader community to ensure reproducibility. User documentation is provided separately.
Mass Assembly of Stellar Systems and Their Evolution with the SMA (MASSES)—1.3 mm Subcompact Data Release
Authors: Stephens Ian W. , Dunham Michael M. , Myers Philip C. , Pokhrel Riwaj , Bourke Tyler L. , Vorobyov Eduard I. , Tobin John J. , Sadavoy Sarah I. , Pineda Jaime E. , Offner Stella S. R. , Lee Katherine I. , Kristensen Lars E. , Jørgensen Jes K. , Goodman Alyssa A. , Arce Héctor G. , Gurwell Mark
Published: July 2018

We present the Mass Assembly of Stellar Systems and their Evolution with the SMA (MASSES) survey, which uses the Submillimeter Array (SMA) interferometer to map the continuum and molecular lines for all 74 known Class 0/I protostellar systems in the Perseus molecular cloud. The primary goal of the survey is to observe an unbiased sample of young protostars in a single molecular cloud so that we can characterize the evolution of protostars. This paper releases the MASSES 1.3 mm data from the subcompact configuration (∼4″ or ∼1000 au resolution), which is the SMA’s most compact array configuration. We release both uv visibility data and imaged data for the spectral lines CO(2–1), 13CO(2–1), C18O(2–1), and N2D+(3–2), as well as for the 1.3 mm continuum. We identify the tracers that are detected toward each source. We also show example images of continuum and CO(2–1) outflows, analyze C18O(2–1) spectra, and present data from the SVS 13 star-forming region. The calculated envelope masses from the continuum show a decreasing trend with bolometric temperature (a proxy for age). Typical C18O(2–1) line widths are 1.45 km s−1, which is higher than the C18O line widths detected toward Perseus filaments and cores. We find that N2D+(3–2) is significantly more likely to be detected toward younger protostars. We show that the protostars in SVS 13 are contained within filamentary structures as traced by C18O(2–1) and N2D+(3–2). We also present the locations of SVS 13A’s high-velocity (absolute line-of-sight velocities >150 km s−1) red and blue outflow components. Data can be downloaded from https://dataverse.harvard.edu/dataverse/MASSES.
Zu Verbreitung und Morphologie einiger Onthophagus-Arten der Schweiz (Coleoptera, Scarabaeidae)
Authors: Krell Frank-Thorsten
Published: July 2018

On distribution and morphology of someOnthophagusspecies in Switzerland (Coleoptera: Scarabaeidae). – On the basis of 1097 specimens from 12 collections, the distribution of ten dung beetle species of the genusOnthophagus(Scarabaeidae) in Switzerland is compiled and shown in distribution maps:O.taurus-group:O.illyricus,O.taurus;O.fracticornis-group:O.fracticornis,O.opacicollis,O.similis;O.ovatus-group:O.baraudi,O.grossepunctatus,O.joannae,O.ovatus,O.ruficapillus. New characters of the female genitalia allow species identification ofO.fracticornis,O.similis, andO.ruficapillus. Reduced male characters of a smallO.gibbulusare described.
Tzeananiaceae, a new pleosporalean family associated with Ophiocordyceps macroacicularis fruiting bodies in Taiwan
Authors: Ariyawansa Hiran A. , Phillips Alan J.L. , Chuang Wei-Yu , Tsai Ichen
Published: July 2018

The order Pleosporales comprises a miscellaneous group of fungi and is considered to be the largest order of the class Dothideomycetes. The circumscription of Pleosporales has undergone numerous changes in recent years due to the addition of large numbers of families reported from various habitats and with a large amount of morphological variation. Many asexual genera have been reported in Pleosporales and can be either hyphomycetes or coelomycetes. Phoma-like taxa are common and have been shown to be polyphyletic within the order and allied with several sexual genera. During the exploration of biodiversity of pleosporalean fungi in Taiwan, a fungal strain was isolated from mycelium growing on the fruiting body of an Ophiocordyceps species. Fruiting structures that developed on PDA were morphologically similar to Phoma and its relatives in having pycnidial conidiomata with hyaline conidia. The fungus is characterised by holoblastic, cylindrical, aseptate conidiogenous cells and cylindrical, hyaline, aseptate, guttulated, thin-walled conidia. Phylogenetic analysis based on six genes, ITS, LSU, rpb2, SSU, tef1 and tub2, produced a phylogenetic tree with the newly generated sequences grouping in a distinct clade separate from all of the known families. Therefore, a new pleosporalean family Tzeananiaceae is established to accommodate the monotypic genus Tzeanania and the species T.taiwanensis in Pleosporales, Dothideomycetes. The Ophiocordyceps species was identified as O.macroacicularis and this is a new record in Taiwan.
La mise en place de l’audit légal dans les universités : quelle(s) légitimité(s) ?
Authors: Chatelin Céline , El Kaddouri Hamza
Published: July 2018

En tant que nouveau dispositif de contrôle au sein des universités, l’audit légal pose la question de sa légitimité pour les parties prenantes et donc de la réussite de sa mise en place au sein d’un système de gouvernance existant. Dans cette recherche nous proposons d’examiner plus particulièrement la question des facteurs d’appropriation de ce nouveau dispositif à partir de l’analyse des formes de légitimité (pragmatique, morale et cognitive) telles que définie par Suchman (1995). Quatorze entretiens semi-directifs ont été menés au sein de deux universités. Les résultats de ces deux études de cas montrent les différents niveaux de légitimité de ce nouveau mécanisme de gouvernance universitaire et ouvrent quelques pistes de réflexion sur l’apport de l’audit légal pour les parties prenantes et par conséquent pour l’efficacité de la gouvernance des universités.
Les pratiques de Gestion des Ressources Humaines au sein des EPLE et les effets possibles sur la performance des établissements
Authors: Fournier Sandrine
Published: July 2018

Dans cet article, nous appréhenderons la notion de performance dans le domaine public et plus particulièrement dans les établissements publics locaux d’enseignement. L’objectif de notre travail réside en la détermination d’un effet possible de la performance humaine sous l’impulsion des pratiques de gestion de la ressource humaine mises en œuvre par les chefs d’établissements. L’originalité de cette étude se trouve dans la difficulté de mettre en avant les outils artéfactuels de gestion publique chez les enseignants. La notion de performance est vécue par eux comme une antinomie au sein du système éducatif où l’attachement à la pédagogie s’oppose à l’esprit consumériste et compétitif.
Peut-on parler d’engagement affectif et d’engagement calculé chez les agents publics africains ?
Authors: Vigan Fanou Arsène
Published: July 2018

Cette recherche vise à analyser la pertinence et la dimensionnalité des engagements affectif et calculé au sens de Meyer et Allen dans un contexte africain. Les résultats de l’analyse factorielle exploratoire et de l’analyse factorielle confirmatoire sur deux échantillons d’agents publics béninois montrent que l’engagement affectif et l’engagement calculé sont des concepts pertinents dans ce contexte. Cependant, contrairement aux études antérieures, l’engagement affectif s’est révélé comme un concept composé de deux sous-dimensions distinctes : l’attachement social et l’attachement aux valeurs organisationnelles. Les deux sous-dimensions généralement trouvées dans la littérature pour l’engagement calculé ont été confirmées. Les implications de ces résultats sont discutées.
Management des biens communs de la connaissance : principes de conception et gouvernance de l’action collective
Authors: Amabile Serge , Peneranda Adrien , Haller Coralie
Published: July 2018

L’étude de l’action collective dans la gestion des biens communs par des communautés auto-organisées est un thème qui a suscité une littérature originale sur la gouvernance et les formes institutionnelles alternatives depuis cinq décennies. La richesse de ces développements a été confirmée par l’attribution du Prix Nobel d’Économie 2009 à E. Ostrom. Les recherches de l’école de Bloomington d’Ostrom ont permis de découvrir plusieurs principes de conception des systèmes de ressources communes qui, lorsqu’ils sont présents, favorisent une gestion collective pérenne de ces ressources. Ces résultats ont montré leur pertinence au-delà des seuls systèmes de ressources physiques. Hess et Ostrom ont ainsi appelé la communauté scientifique à s’intéresser à la gestion collective des connaissances vues comme une ressource partagée. Cet article propose de répondre à cet appel en explorant les possibilités d’adaptation du cadre d’analyse des biens communs à des situations de coopération dans lesquelles des acteurs gèrent des informations mutualisées. La question de recherche étudiée a pour objectif de comprendre comment des individus peuvent s’auto-organiser au moyen d’institutions durables pour gérer la production et l’utilisation de connaissances communes. Nous avons mené cinq études de cas en mobilisant une méthodologie de recherche qualitative. Les résultats montrent que le fonctionnement sur le long terme des collectifs auto-organisés s’inscrivant dans le cadre conceptuel d’Ostrom semble conduire à une gestion durable et efficiente de la ressource informationnelle.
Le cas de la communauté de pratique en innovation pilotée par le Groupe SEB
Authors: Arzumanyan Lusine , Angué Katia
Published: July 2018

Dans une ère de changement continu, les entreprises qui réussissent sont celles qui créent constamment de nouvelles connaissances et les diffusent largement au sein de toute l’entreprise pour les intégrer ensuite dans de nouveaux produits, services ou procédés. Dans ce contexte, de nombreuses entreprises multinationales mettent en place des communautés de pratique qui favorisent l’apprentissage, le développement et le partage des connaissances et conduisent à la création d’un environnement propice à la créativité et l’innovation. Cette recherche vise à contribuer à une meilleure compréhension des processus de mise en place et de développement d’une communauté de pratique en innovation. L’étude empirique, conduite au sein du Groupe SEB, concerne une communauté de pratique en innovation. Les données ont été collectées à travers 63 entretiens semi-directifs, complétés par une observation directe et l’analyse de documents internes. Les résultats obtenus mettent en exergue l’existence de quatre phases caractérisant la mise en place et le développement d’une communauté de pratique.
Comprendre l’interaction des patients membres d’une communauté virtuelle de santé et son impact sur la relation que le patient entretient avec son médecin
Authors: Menvielle Loick , Menvielle William , Audrain-Pontevia Anne-Francoise
Published: July 2018

Cette recherche s’inscrit dans le cadre du développement de la digitalisation de la santé et de l’émergence de communautés virtuelles de santé. Elle vise à étudier les relations causales entre la crédibilité et l’attitude à l’égard de plateformes virtuelles de santé ainsi qu’entre la confiance et l’attitude vis-à-vis du médecin. Un questionnaire a été développé et diffusé en ligne auprès de patients et utilisateurs de communautés virtuelles médicales. Les données collectées ont permis de procéder à des analyses confirmatoires sous SPSS et AMOS pour les équations structurelles. Les résultats montrent que la confiance interpersonnelle émanant des communautés virtuelles de santé entretient une relation positive avec la crédibilité et l’attitude à l’égard de ces communautés virtuelles. Il en est de même pour l’attitude à l’égard du médecin. La crédibilité accordée à ces communautés virtuelles de santé a une relation positive sur l’attitude à l’égard ces plateformes. En revanche, la relation s’avère être négative entre la crédibilité et l’attitude à l’égard du médecin. Enfin, seule l’attitude vis-à-vis du médecin a une relation positive avec la confiance vis-à-vis du médecin. Cette recherche est la première mesurant les relations entre crédibilité, confiance et attitude. Par ailleurs, elle permet de mieux considérer le rôle des utilisateurs des communautés virtuelles de santé et des médecins, afin d’améliorer l’attitude des patients à l’égard des médecins.
“Too Fast, Too Furious” ? Trading algorithmique et instabilité des marchés financiers
Authors: Arena Lise , Oriol Nathalie , Veryzhenko Iryna
Published: July 2018

En quoi les stratégies de trading algorithmique peuvent-elles expliquer la propagation de flash crashes sur le marché financier ? L’originalité de traiter cette question réside dans le besoin de croiser deux champs disciplinaires : la finance de marché et la gestion des systèmes d’information. Cet article se fonde sur une approche de simulation multi-agents construite à partir d’une catégorisation réaliste des stratégies des traders, de leurs recours aux systèmes de trading algorithmique et du rôle des systèmes transactionnels d’appariement au niveau du marché. Parmi les résultats exposés, nous montrons qu’en favorisant les stratégies fondées sur la vitesse, l’usage des nouvelles technologies peut porter atteinte à la résilience et à la stabilité des marchés face à de potentiels chocs opérationnels intra journaliers. Nous montrons également, à travers l’illustration de la décimalisation, les conséquences d’un changement de règle sur l’anatomie du crash, et le rôle des systèmes de traitement transactionnels dans la propagation de ces crises financières d’un genre nouveau.
Influencia de la soldadura de raíz con ERNiCrMo-3 en las propiedades de las uniones soldadas de fundición nodular
Authors: Pascual-Guillamón Manuel , Cárcel-Carrasco Javier , Pérez-Puig Miguel Á. , Salas-Vicente Fidel
Published: July 2018

Este artículo estudia el efecto de la soldadura de raíz (GTAW) con ERNiCrMo-3 sobre la microestructura y propiedades mecánicas de una unión de fundición nodular cuando las pasadas de la cubierta se realizan con la técnica SMAW con electrodos de Ni. Para tener una mejor comprensión de los resultados, se comparan con las características de una soldadura completa de Ni SMAW. Esto se hizo antes y después de un recocido a 900 °C con el fin de evaluar las influencias y los posibles beneficios de este tratamiento térmico. Los resultados muestran que la presencia de una soldadura de raíz de GTAW ERNiCrMo-3, a pesar de la mejora de la penetración, conduce a una pérdida de propiedades mecánicas en la soldadura de raíz que, incluso con un recocido, no es posible eliminar.
Experience of Ubiquitous Computing Technology Driven Mobile Commerce in Africa: Impact of Usability, Privacy, Trust, and Reputation Concern
Authors: Olaleye Sunday Adewale , Oyelere Solomon Sunday , Sanusi Ismaila Temitayo , Agbo Joseph Friday
Published: July 2018

The concept of ubiquitous computing allows the seamless: anywhere, anytime, anyone interaction of computing devices and technology. Ubiquitous commerce simply known as u-commerce is an evolution of commerce based on recent innovations and advancement in computing technology. The aim of this study is to understand the impact of ubiquitous computing technologies on users, with a special focus on ubiquitous commerce. The study used the quantitative method and targeted the mobile device users for online shopping in Nigeria with convenience sampling technique. The data collected was analyzed using SmartPLS 2.0 with partial least square structural equation modelling. The study results confirmed the significant role of trust as a mediator between the reputation and u-commerce user’s experience, and usability and privacy directly predict the ubiquitous commerce user’s experience.  The study advances with managerial implications and finally pinpoint the limitations and propose future studies.
Design Guidelines for Creating Mobile Language Learning Applications
Authors: Jamaldeen Fazeena , Hewagamage Priyantha , Ekanayaka Yamaya
Published: July 2018

Mobile devices have proven to be an appropriate tool which expands the horizons of learning beyond the classroom through means of flexibility and portability. Throughout this study, the authors have worked with a set of design guidelines which were derived from the literature. The artifact developed considering these design guidelines has been evaluated among various user groups for better understanding of m-learning as a tool to support English Language Learning. Findings of these evaluations have been used to improve the design guidelines.  The authors also identify the effectiveness of mobile learning as a supporting medium of learning and as a primary medium of learning among different learner groups, which is another outcome of this study. 
Smartphone Based Image Color Correction for Color Blindness
Authors: Elrefaei Lamiaa A.
Published: July 2018

Color blind is a type of Color Vision Deficiency, which is the inability that a person could not realize the differences between some colors. There are three types of color blindness: Monochromacy, Dichromacy, and Anomalous Trichromacy. Color blind cannot be cured. Today, technology gets up with solutions to help people with color blindness to see the image and distinguish between the different colors using some algorithms. This paper presents a smartphone based experimental comparison of color correction algorithms for Dichromacy color-blind viewers. This comparison includes LMS Daltonization algorithm, Color-blind Filter Service (CBFS) algorithm, LAB color corrector algorithm, and the shifting color algorithm. The description of the smartphone based implementation details and parameters settings of these algorithms is presented. An application interface is implemented to enable the user to choose the algorithm that gives the most appropriate results. The results of these algorithms are compared to see their strength and weakness.
Designing a Mobile Application for Structured and Flexible Interview Data Collection in the Health Domain
Authors: Svarre Tanja , Kirkegaard Lunn Tine Bieber
Published: July 2018

The purpose of this paper is to report on the design of an Android tablet application for data collection by occupational therapists. The design emerged from two design workshops held with users experienced in collecting data on the challenges clients face in using technologies in their daily lives. On the basis of information gathered in the workshops, an Android application was developed for use in clinical and research settings. The aim was to ease the data-collection process and improve data quality by digitizing an existing analogue tool.
A Systematic Review of Learning Through Mobile Augmented Reality
Authors: Hedberg Hillevi , Nouri Jalal , Hansen Preben , Rahmani Rahim
Published: July 2018

In the beginning of 2000, researchers started to see the potential of using Augmented Reality (AR) in educational and foresaw that further research within the field. Since then, AR research have taken many different approaches. This is also true for AR in relation to pedagogical purposes. This study is to investigate what has been studied within the AR field related to mobile augmented reality. It attempts to make systematic review of how learning and pedagogical aspects have been approached in the articles. In recent years, mobile augmented reality has become increasingly interesting due to the mobile devices small form factors and their ability to let the students move around freely while learning. The aim of this study is to make a systematic review of pedagogical uses of mobile augmented reality. Based on a review of previous literature of mobile AR systems for pedagogical purposes, published between 2000-2017, make it possible to see in which direction mobile AR systems for education are heading and how future mobile AR systems should be designed to best fit the needs of future students so they can more effectively improve their learning.
Dynamics between Disturbances and Motivations in Educational Mobile Games
Authors: Nygren Eeva Liisa , Laine Teemu H. , Sutinen Erkki
Published: July 2018

Understanding engagement in games provides great opportunities for developing motivating educational games. However, even good games may induce disturbances on the learner. Therefore, we go further than presenting only results and discussion related to the motivation aspects and disturbance factors of the playing experience in UFractions (Ubiquitous fractions) storytelling mobile game. Namely, we define the dynamics between these two important game features. Sample of the case study was 305 middle school pupils in South Africa, Finland, and Mozambique.

Guidelines for game developers, users and educators were derived from the interplay of disturbance factors and motivations. Furthermore, we defined six different learning zones deriving from disturbances the player is facing and the player’s motivation level.
The Design and Implementation of a Mathematics Game-Base Learning Application for Primary Students
Authors: Aljojo Nahla
Published: July 2018

The traditional learning process used in schools is outdated.  Students nowadays spend most of their time using technologies for entertainment and to communicate with their friends.  Technology can also be used to present opportunities in teaching difficult subjects, such as mathematics, in a better environment. This project aims to improve the mathematical skills of addition and subtraction in young children aged 6 to 8 by combining education and entertainment in a simple math learning game.  Using ideas from Jerome Bruner’s theory, and Bloom’s Taxonomy of cognitive goals, this application will help children learn and interact effectively with the world around them. This project presents the design and development of a game-based learning application that improves the mathematical skills of young children.  Specifically, our target-users for this application are primary school students who are learning addition and subtraction. This paper provides discussion and guidance on how to evaluate the impact of Mathematics Game-Base Learning Application. The overall results of the experimental study indicate a positive effect of Mathematics Game-Base Learning Application on the learning process.
Mobile Application Design Emergency Medical Call for the Deaf using UCD Method
Authors: Risald Risald , Suyoto Suyoto , Santoso Albertus Joko
Published: July 2018

Deaf or hearing loss is a condition of inability to hear something, either totally or partially. Hearing loss greatly affects the life of a person in communicating with the people around him. Deaf people will be very difficult when in a medical emergency, this is because the medical emergency situation requires fast action.

          The Healthy Phone application is a mobile medical emergency call application that can help people with hearing impaired when in emergency situations. With the Healthy Phone application, the user only needs to select an icon that suits the situation encountered in touchscreen mobile device then the message will be sent to the nearest hospital.
                To search for icons corresponding to emergencies, the User Centered Design (UCD) method is used. This application is very helpful for deaf people because this application does not require audio communication and user location is also sent automatically to the nearest hospital. The results were analyzed using four emergency event scenarios with a total score of 87% and an average user time of less than 0:42 sec indicating that the study was successful in designing a mobile medical emergency call application according to user requirements.
Study on the Enhanced Superplasticity of Mg-Li Based Alloy by a Stepped Deformation Method
Authors: Fu M.W. , Yang H.P. , Chen P. , Zhang X. , Wang G.C.
Published: July 2018

A two-step deformation approach is proposed for the superplastic deformation (SPD) of Mg-9Li-1Al (LA91) alloy. This method has been successfully applied to titanium alloys and has induced enhanced superplasticity, and the feasibility of the method for the Mg-Li based alloy is explored. In a previous research, single-step SPD of LA91 alloy has been investigated, and the highest elongation of 563.7% was obtained by using the 8-pass equal channel angular extruded material, by the maximum strain rate sensitivity (Maxm) mode deformation. While in this research, the raw material in the as-extruded state is utilized. Constant velocity (Constv) and constant strain rate (CSR) modes are adopted for the first step of the deformation, respectively, with the elongation of the first step from 50% to 150%. The Maxm mode, in which the strain rate sensitivity m is always kept to be the maximum value, is applied to the second step. In addition, single-step tests by Constv, CSR and Maxm modes until fracture are conducted. The experimental temperature is 300°C, which was proved to be the optimum temperature for the SPD of this material in the previous research. The result shows that the 2-step method can greatly improve the superplasticity of the LA91 alloy, especially for the CSR mode deformation, and the maximum elongation obtained is 535.3%, by the CSR-Maxm mode, which is comparable to the optimum result in the previous research.
Superplasticity of Al-Mg-Zr Alloy
Authors: Mochugovskiy Andrey , Mikhaylovskaya Anastasia V. , Mufalo Walubita , Portnoy Vladimir K.
Published: July 2018

The microstructure and superplasticity of the thermomechanically proceeded sheets of Al - 3wt.%Mg - 0.25wt.%Zr were investigated. High density of L12-structured fine dispersoids of Al3Zr metastable phase was observed by TEM analysis. Alloy demonstrated high recrystallization resistance at elevated temperature due to Al3Zr dispersoids. The tensile tests were carried out in a temperature range of 440-500 °C and a strain rate of 1×10-3to 1×10-2s-1. The maximum elongation to failure of 370% was observed at 480 °C at the constant strain rate values of 2×10-3and 5×10-3s-1.
On Mechanisms of “Grain Boundary Sliding”, in Light of the Kaibyshev-Valiev Data on Two Limit “Non-Equilibrium” GB States in Deformed Metallic Materials
Authors: Nechaev Yuriy S.
Published: July 2018

Based on the results of the thermodynamic analysis of a number of experimental data, and in the light of the Kaibyshev-Valiev discovery, the possibility of periodic formation of a liquid-like state in the nanoregions of extremely "non-equilibrium" grain boundaries and in other structural defect regions in metallic polycrystals during their superplastic deformation and intense plastic deformation is considered. It is also considered important differences between the liquid-like state and the glass-like (amorphous) state.
Low-Temperature Superplasticity of the Ni-Based EK61 Superalloy and Application of this Effect to Obtain Sound Solid Phase Joints
Authors: Galieva Elvina , Valitov Vener , Lutfullin Ramil , Bikmukhametova Aerika
Published: July 2018

It is shown that formation of ultrafine-grained structure in EK61 superalloy up to grain sizes less than 1 μm provides to realize superplastic properties. The influence of deformation in the temperature range 600-1100 °C and strain rate range 10-4s-1– 10-3s-1on the microstructure and properties of ultrafine-grained nickel-based alloy EK61 is studied. It is established that in temperature range 750-900 °C the alloy demonstrates superplasticity (SP) characteristics: strain rate sensitivity factor “m” correspond to 0.39-0.59, stable structure and low changes in the form and size of grains. The maximum SP is displayed at temperatures of 800 °C, wherein the elongation is 1431 %. It has been experimentally confirmed that the use of low-temperature superplasticity is a promising for processing sound solid phase joints by pressure welding of similar and dissimilar Ni-based superalloys.
Microstructure Homogeneity in AA6063 Alloy Processed by Cyclic Expansion Extrusion
Authors: Babu V. , Balasivanandha Prabu S. , Padmanabhan K. Anantha
Published: July 2018

Aluminium (AA6063) alloy was subjected at 200oC to cyclic expansion extrusion (CEE) - a severe plastic deformation (SPD) process - up to 10 passes. The extrusion die angle is 22.5o. Microstructure examination revealed evidence for grain refinement, which had reduced from 20μm±5.8 (average) in the parent material to 4.8 μm±1.4 (average) after 10 passes (i.e. ~76% of reduction). The microhardness and tensile strength had increased, while the elongation decreased with the number of passes. The specimen after 4 passes had the highest hardness of 591 HV (about 40% improvement) and the highest tensile strength value of 153 MPa which is ~23% more than that of the parent material. The hardness and tensile strength values decrease marginally on further processing, although throughout they are higher than that of the parent material. With increasing of number of passes, grain refinement and the fraction of high-angle boundaries continued to increase, which in the end was ~ 40%.
Novel Method of Severe Plastic Deformation - Continuous Closed Die Forging: CP Aluminum Case Study
Authors: Zhilyaev Alexander P. , Rodriguez Sandra , Calvo Jessica , Cabrera Jose María
Published: July 2018

There is a large number of methods for severe plastic deformation (SPD). Multidirectional forging (MDF) is probably one of the most easily scalable for industrial application. In general, two main conditions need to be fulfilled for successful SPD processing: constant sample geometry and application of a quasi-hydrostatic pressure. The first condition is necessary for strain accumulation by repetitive deformation and the second one helps preventing cracking in the specimens with high accumulated strain. However, MDF is not providing quasi-hydrostatic condition in the processed sample. This paper reports a novel method for severe plastic deformation, namely continuous closed die forging (CCDF), which fulfils both requirements for the successful deformation of samples to a very high accumulated strain. Commercially pure aluminum (1050) was processed to a total strain of 24 by CCDF. After processing, the microstructure was refined down to a mean grain size of 0.78 μm. Tensile testing showed good mechanical properties: yield strength and ultimate tensile strength of the ultrafine-grained aluminum were 180 and 226 MPa, respectively. Elongation to rupture was about 18%. The microstructure, microhardness and grain boundary statistics are discussed with regard to the high mechanical properties of the UFG aluminum processed by this novel method.
On the Hierarchy of Structural-Phase States of 1561 Aluminum Alloy
Authors: Pazylov Shakir T.
Published: July 2018

An experimental issue of studying the structural and deformation properties of an initially anisotropic 1561 alloy within a wide temperature-rate range is considered. In the course of realization of the experiments on “Gagarin’s” samples cut out in the rolling direction, the circular cross sections of the samples took an elliptical form. As a macro-characteristic of the material reflecting the occurring structural changes, the anisotropy factor is taken, which is represented by the ratio of deformations measured along the small and large axes of the cross section. Previously unknown regularities of the change in the anisotropy factor were established at the temperature increase under different values of the degree and strain rate. An essential dependence of the anisotropy factor on the thermomechanical conditions of deformation is noted. At high homological temperatures, the thermal range corresponding to the manifestation of superplastic properties is identified. Here, the anisotropy index tends to a minimum value. A correspondence between the results of mechanical experiments and the study of the structural state of the alloy was established. The obtained results indicate the dependence of the anisotropy factor on the initial structure of the alloy. The anisotropy factor can be taken as one of the macroparameters of the material that correspond to structural transformations and allow one to quantify the degree and completeness of structural changes relative to the initial state in a changing field of temperatures and strain rates.
Friction Stir Processing Trials of SP-700 (Ti-4.5Al-3V-2Fe-2Mo) Titanium Alloy
Authors: Tabatabaei Hamed Mofidi , Okuyama Chiaki , Nishihara Tadashi , Ohashi Takahiro
Published: July 2018

Superplastic titanium alloy (SP-700 with nominal composition of Ti-4.5Al-3V-2Fe-2Mo) an alpha-beta alloy, with a beta-rich fine microstructure and excellent superplastic formability has wide applications in aerospace components, metal wood heads, tools, automotive components. However, very little information is available regarding friction stir processing (FSP) characteristics of this alloy. This study discusses the trials of FSP of this highly formable titanium alloy. Results are discussed in terms of hardness and temperature measurements and microstructural observations.
On the Effect of the Complexity of the Constitutive Model in Simulating Superplastic Forming
Authors: Dai Guang Wen , Jarrar Firas , Ozturk Fahrettin , Sheikh-Ahmad Jamal
Published: July 2018

Accurate constitutive material models are essential for the realistic simulation of metal forming processes. However, for superplastic forming (SPF), mostly the material models found in literature are based on the fitting of the simple power law equation. In this study an investigation was carried out on the effect of the complexity of the constitutive model on the accuracy of the SPF simulation results. This was achieved by following an experimental-numerical investigation of the SPF of the AZ31B magnesium alloy. High temperature bulge forming tests and microstructural analyses were carried out to generate the data required to fit two different constitutive models. The first is the simple power law. The second model takes into account grain growth and cavity formation in addition to the strain and strain rate hardening. The two models were then implemented in the simulation of SPF of a car-shaped geometry and the results were compared with those obtained from actual forming experiments. Results show that both models are capable of predicting the thickness distribution and the shape of the formed part to an acceptable degree. However, the more complicated model shows a better capability in predicting the forming time required to achieve the part geometry.
Superplasticity of Aerospace 7075 (Al-Zn-Mg-Cu) Aluminium Alloy Obtained by Severe Plastic Deformation
Authors: Carreño Fernando , Ruano Oscar A.
Published: July 2018

The 7075 (Al-Zn-Mg-Cu) aluminium alloy is the reference alloy for aerospace applications due to its specific mechanical properties at room temperature, showing excellent tensile strength and sufficient ductility. Formability at high temperature can be improved by obtaining superplasticity as a result of fine, equiaxed and highly misoriented grains prone to deform by grain boundary sliding (GBS). Different severe plastic deformation (SPD) processing routes such as ECAP, ARB, HPT and FSP have been considered and their effect on mechanical properties, especially at intermediate to high temperatures, are studied. Refined grains as fine as 100 nm and average misorientations as high as 39o allow attainment of high strain rate superplasticity (HSRSP) at lower than usual temperatures (250-300oC). It is shown that increasing misorientations are obtained with increasing applied strain, and increasing grain refinement is obtained with increasing processing stress. Thus, increasing superplastic strains at higher strain rates, lower stresses and lower temperatures are obtained with increasing processing strain and, specially, processing stress.
Formability Analysis on Superplastic Forming of AZ91 Magnesium Alloy Sheet
Authors: Kumaresan G. , Kalaichelvan K.
Published: July 2018

Superplastic sheet metal forming allows the production of complex parts that are not formable under normal conditions. Superplastic sheet metal forming processes are normally based on the same common principle: the sheet metal is firmly clamped between the die halves and is blow-formed by means of gas pressure. Generally superplastic forming can only be achieved in a very narrow range of strain rates and temperature. Superplastic materials are relatively stable when deformed; this behavior is related to the observation that the flow stress of a superplastic material is very sensitive to the rate of deformation. This paper aims to study the formability characteristic of Magnesium alloy by considering variable parameters, such as the sheet thickness, forming pressure and forming temperature. The forming time of 120 minutes is constant for the formability test. Keywards: Multi dome test, superplasticity, Mg – alloy, Thermomechanical processing, Formability.
Influence of Structural-Phase State on Low-Temperature Superplasticity of Ultrafine-Grained Titanium Alloys
Authors: Ratochka Ilya V. , Naydenkin Evgeny V. , Mishin Ivan , Lykova Olga
Published: July 2018

The influence of the structural-phase state on the development of low-temperature superplasticity of titanium alloys with an ultrafine-grained structure and different volume fraction of the β phase was studied. It was shown that the formation of the structure by multi-directional pressing leads to a decrease in the temperature of the beginning of the superplastic flow realization up to 823K regardless of phase composition of the titanium alloys. It is assumed that the non-monotonic character of the temperature dependence of relative elongation to failure of the Ti-4Al-2V and Ti-6Al-4V alloys is related to their transition to a fine-grained state with an increase in the deformation temperature. It was established that the character and volume fraction of the β-phase precipitations have a significant effect on the grain growth and the temperature dependence of the relative elongation of the alloys to failure under conditions of superplasticity.
Microstructure and Bending Strength of Dissimilar SS400/SUS304 Steels T-Fillet Joint by Gas Metal Arc Welding
Authors: Kimapong Kittipong , Triwanapong Surat
Published: July 2018

In this paper, experiments on welding a dissimilar SS400/SUS304 steel T-fillet joint using high chromium electrode, and an effect of welding current on joint properties were studied. T-joints wielded by the designed specific welding currents were mechanically prepared and systematically investigated for joint properties. The experimental results were summarized as follows. Dissimilar SS400/SUS304 steels T-fillet joint could be successfully welded using a gas metal arc welding process with no defect in a weld metal. The optimized welding current in this experiment was 160 A that showed the least crack length of 0.247 mm. from a bending test. A different chemical composition of low carbon steel and high chromium weld metal produced a small interface shown with a smaller mixed zone of reinforced elements and base metal. It was also affected to decrease in the joint strength. However, the increase in the welding current could increase a combination of reinforced elements and a base metal on the interface, and it showed an effect to increase in the joint strength.
Shear Strength and Fracture Location of Dissimilar A6063 Aluminum Alloy and SUS430 Stainless Steel Lap Joint
Authors: Yaemphuan Paiboon , Triwanapong Surat , Kimapong Kittipong
Published: July 2018

In this paper, friction stir welding (FSW) was used to weld the dissimilar A6063 Aluminum/SUS430 stainless steel lap joint with various parameter setting in a welding process. The setting included a rotating speed between 125-750 rpm, a welding speed between the 25-175 mm/min and 0-5 degrees of tool tilted angle. The welded lap joints were systematically examined in regard of the tensile-shear strength, the fracture path, and microstructure. The experimental results were concluded as follows. The decrease in the welding heat input generated from the low rotating speed and the high welding resulted in decreasing of the shear strength. A degree of a tool tilted angle affected a shear strength, and a change in the strength came from the different rate in material combination at the joint interface. The increase in a tensile-shear strength occurred for specimens produced in 0-2 degrees of a tool tilted angle while 3-5 degrees affected in decreasing. The highest shear strength of 11,870 N was obtained when the lap joint was produced by the rotating speed of 500 rpm, the welding speed of 50 mm/min and the tool tilted angle at 2 degrees. The fracture path found in the specimen with the maximum shear strength was located in the Al stirred zone, not in the joint interface.
Study on Mechanical Properties of Steel on Transmission Tower under Icing Load
Authors: Liu Chun Cheng , Huang Da Peng , Zhang Yi Ling , Yang Geng , Qu Da , Lv Chun Lei
Published: July 2018

In order to determine the failure mode of high-voltage transmission tower materials under the condition of ice-coating load in an actual line. The Qidian-Luoping 500kV wine glass type transmission tower is selected as the prototype, and the one tower with two lines model of the whole beam unit is established by using the ANSYS finite element software. The loading mode is static load considering icing load and wind load. The most unfavorable wind direction of the transmission tower is obtained by comparing and analyzing the maximum displacement and the stress of the rod under different directions of wind load in the transmission tower. Then the failure mode of transmission tower is studied by the variable ice thickness of the tower line system. The results show that the direction parallel to the cross arm is the most unfavorable direction in the transmission tower. And under the most unfavorable wind direction, with the increase of ice thickness, it is found that the tower head part is more sensitive to icing load than the tower body part. When the thickness of ice coating reaches 30mm, the weak load-bearing rod will appear locally in the transmission tower and the position of the rod is mainly distributed on the outer upper crank arm, the outer side of the ground bracket and the upper side of cross arm of the transmission tower.
Elastic Strength of Defective Steel Bolt Group under Eccentric Load Design
Authors: Yang Jen Jen , He Kun Ze , Hsu Wei Ting
Published: July 2018

Steel bolt groups are often used for joining steel structures. The design strength of the steel bolt group is related to the geometric distribution, the eccentric load distance, the material strength and the load angle, thus making the analysis complicated and not easy for the user. The existing analysis methods are two kinds of elasticity and ultimate analysis. Both methods consider the stress distribution of each steel bolt and find the steel bolt at the critical position is obtained, the design load analysis is deduced. This study will consider the geometric distribution of steel bolting group affected, for a row, two rows, three rows and four rows of bolt group, considering different eccentric distance and angle of influence. Using a simple elastic analysis method to Studied the strength analysis results produced when a corner bolt is damaged due to a defect. The results show that the greater the eccentric load distance, the lower the design strength, and the load change on the vertical is more obvious than the horizontal. When the corner of the steel bolt group is removed, its design strength is likely to decrease, but at low eccentricity distance and large angles, the strength of the complete bolt is higher. This study organizes the design method of steel bolts and reviews the geometric rules of the bolt group analysis. It founded that the regular geometry needs to be reviewed in the case of large eccentric loads with small eccentricities. This study for the bolt connections strength of a certain understanding and awareness, expect the future for the safety of steel structure contribute.
Experimental Study on Post Fire Tensile Properties of Reinforcing Rebars Connected by Grout-Filled Splice Sleeves
Authors: Liu Yong Jun , Zeng Qing Hong , Liu Hong Ru , Wang Shuo Xun
Published: July 2018

This paper presents some experimental results of tensile properties of reinforcing bars spliced by grout-filled coupling sleeves after exposed to fires to identify the effect of temperature histories on tensile properties of spliced reinforcing bars, which provide a useful base for assessing structural behaviors of precast reinforced concrete buildings damaged by fires. A spliced rebar system investigated in this paper consists of two equal-diameter steel reinforcing bars with 25mm diameter and a straight coupling sleeve with 55mm outer and 42mm inner diameters. As a result, the thickness of grout between internal steel bars and outer sleeves are 8.5mm. Five test specimens are manufactured in identical technology and divided into three groups. First group is reference group consist of just one specimen which is not exposed to fire. Second and third groups consist of two specimens that are exposed to ISO 834 standard fire in furnace for 15 and 25 minutes respectively. The temperature-time curves of grout between rebars and sleeves are measured via thermocouples embedded in grout. Subsequently, a universal testing machine is used to test the ultimate load bearing capacities of five specimens. Test results demonstrate that ultimate load bearing capacities of steel rebars spliced by grout-filled sleeves are considerably reduced due to fire damaged grout.
Surface Characteristics of Dentin Derived Hydroxyapatite Coated Layer on Titanium by RF Magnetron Sputtering
Authors: Moon Jong Wook , Na Eui Ri , Kim Young Joon
Published: July 2018

The aim of this study was to evaluate surface characteristics and biological properties of the dentin derived hydroxyapatite (DDHA) coating on titanium substrate. DDHA was derived from extracted human teeth with calcination method at 850°C. The commercially pure titanium was used as a metallic substrate and a RF magnetron sputtering method was used as a coating method. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDX) were performed to investigate the morphology and composition of coating surface. Atomic Forced Microscopy (AFM) and surface profiler were used to assess the surface morphology and roughness. Corrosion tests were performed in phosphate buffered saline at a 36.5±1°C in order to determine the corrosion behavior of the uncoated and coated surface samples. The biocompatibility of DDHA coating surface samples with murine osteoblastic cells was assessed by SEM. As a results, thin coating layer was observed on SEM images and uniformly cover the surfaces without change of titanium substrate. The EDX analysis of this coating surface indicated the presence of Ca, P elements. The mean surface roughness of cp-Ti and DDHA coating samples was 0.27μm, 1.7μm, respectively. The corrosion test indicated the stable passive film on coating samples. SEM observations of murine osteoblastic cells on coating surface showed that cells have proliferated and developed a network of dense interconnections. These results suggest that DDHA coating with RF magnetron sputtering method has good surface characteristics and biocompatibility.