bluuebunny/crossref_metadata_2025 huggingface dataset:
Photovoltaic Power Forecasting Based on EEMD and a Variable-Weight Combination Forecasting Model
Authors: Wang Hui , Sun Jianbo , Wang Weijun
Published: July 2018

It is widely considered that solar energy will be one of the most competitive energy sources in the future, and solar energy currently accounts for high percentages of power generation in developed countries. However, its power generation capacity is significantly affected by several factors; therefore, accurate prediction of solar power generation is necessary. This paper proposes a photovoltaic (PV) power generation forecasting method based on ensemble empirical mode decomposition (EEMD) and variable-weight combination forecasting. First, EEMD is applied to decompose PV power data into components that are then combined into three groups: low-frequency, intermediate-frequency, and high-frequency. These three groups of sequences are individually predicted by the variable-weight combination forecasting model and added to obtain the final forecasting result. In addition, the design of the weights for combination forecasting was studied during the forecasting process. The comparison in the case study indicates that in PV power generation forecasting, the prediction results obtained by the individual forecasting and summing of the sequences after the EEMD are better than those from direct prediction. In addition, when the single prediction model is converted to a variable-weight combination forecasting model, the prediction accuracy is further improved by using the optimal weights.
Synthetic Pollutograph by Prediction Indices: An Evaluation in Several Urban Sub-Catchments
Authors: García Juan T. , Espín-Leal Pablo , Vigueras-Rodríguez Antonio , Carrillo José M. , Castillo Luis G.
Published: July 2018

A generalized methodology applicable to any urban sub-catchment to calculate the pollution curve due to combined sewer overflows would help to implement integrated management policies to reduce urban impacts on the environment. An existing methodology to predict the pollutographs associated to rainfall events is tested in five different sub-catchments with very different pluviometry. Ninety-three rainfall events have been considered by measuring the in-sewer turbidity along the runoff episodes. Such data is then evaluated to obtain two prediction indices: the time to peak of pollutograph ITPP, and the maximum turbidity concentration ICMAX. These indices may be used with linear regressions to calculate the characteristics of pollutographs, such as the time to the peak, TPP, the maximum concentration of turbidity, CMAXtb, and the time to descent, TDP. These parameters allow to estimate the pollutographs of a sub-catchment. The comparison between pollutographs measured in the Ensanche sub-catchment and those calculated with the methodology shows a good agreement in terms of the root mean square deviation between samples and estimated values with the model proposed. Hence, the methodology could be a key way to find synthetic pollutographs for any sub-catchment.
Redox Biology of Respiratory Viral Infections
Authors: Khomich Olga A. , Kochetkov Sergey N. , Bartosch Birke , Ivanov Alexander V.
Published: July 2018

Respiratory viruses cause infections of the upper or lower respiratory tract and they are responsible for the common cold—the most prevalent disease in the world. In many cases the common cold results in severe illness due to complications, such as fever or pneumonia. Children, old people, and immunosuppressed patients are at the highest risk and require fast diagnosis and therapeutic intervention. However, the availability and efficiencies of existing therapeutic approaches vary depending on the virus. Investigation of the pathologies that are associated with infection by respiratory viruses will be paramount for diagnosis, treatment modalities, and the development of new therapies. Changes in redox homeostasis in infected cells are one of the key events that is linked to infection with respiratory viruses and linked to inflammation and subsequent tissue damage. Our review summarizes current knowledge on changes to redox homeostasis, as induced by the different respiratory viruses.
Pectobacterium atrosepticum Phage vB_PatP_CB5: A Member of the Proposed Genus ‘Phimunavirus’
Authors: Buttimer Colin , Lucid Alan , Neve Horst , Franz Charles M. A. P. , O’Mahony Jim , Turner Dann , Lavigne Rob , Coffey Aidan
Published: July 2018

Pectobacterium atrosepticum is a phytopathogen of economic importance as it is the causative agent of potato blackleg and soft rot. Here we describe the Pectobacterium phage vB_PatP_CB5 (abbreviated as CB5), which specifically infects the bacterium. The bacteriophage is characterized in detail and TEM micrographs indicate that it belongs to the Podoviridae family. CB5 shares significant pairwise nucleotide identity (≥80%) with P. atrosepticum phages φM1, Peat1, and PP90 and also shares common genome organization. Phylograms constructed using conserved proteins and whole-genome comparison-based amino acid sequences show that these phages form a distinct clade within the Autographivirinae. They also possess conserved RNA polymerase recognition and specificity loop sequences. Their lysis cassette resembles that of KP34virus, containing in sequential order a U-spanin, a holin, and a signal–arrest–release (SAR) endolysin. However, they share low pairwise nucleotide identity with the type phage of the KP34virus genus, Klebsiella phage KP34. In addition, phage KP34 does not possess several conserved proteins associated with these P. atrosepticum phages. As such, we propose the allocation of phages CB5, Peat1, φM1, and PP90 to a separate new genus designated Phimunavirus.
Multivariate Chemometric Analysis of Membrane Fouling Patterns in Biofilm Ceramic Membrane Bioreactor
Authors: Kulesha Olga , Maletskyi Zakhar , Ratnaweera Harsha
Published: July 2018

Membrane fouling highly limits the development of Membrane bioreactor technology (MBR), which is among the key solutions to water scarcity. The current study deals with the determination of the fouling propensity of filtered biomass in a pilot-scale biofilm membrane bioreactor to enable the prediction of fouling intensity. The system was designed to treat domestic wastewater with the application of ceramic microfiltration membranes. Partial least squares regression analysis of the data obtained during the long-term operation of the biofilm-MBR (BF-MBR) system demonstrated that Mixed liquor suspended solids (MLSS), diluted sludge volume index (DSVI), chemical oxygen demand (COD), and their slopes are the most significant for the estimation and prediction of fouling intensity, while normalized permeability and its slope were found to be the most reliable fouling indicators. Three models were derived depending on the applied operating conditions, which enabled an accurate prediction of the fouling intensities in the system. The results will help to prevent severe membrane fouling via the change of operating conditions to prolong the effective lifetime of the membrane modules and to save energy and resources for the maintenance of the system.
Li-Ion Battery Lifetime Model’s Influence on the Economic Assessment of a Hybrid Electric Bus’s Operation
Authors: Martinez-Laserna Egoitz , Herrera Victor , Gandiaga Iñigo , Milo Aitor , Sarasketa-Zabala Elixabet , Gaztañaga Haizea
Published: July 2018

The present paper is focused on the evaluation of the economic influence of a battery lifetime model upon the optimal sizing and energy management strategy of a dual energy storage system (ESS) composed of Lithium-ion batteries and supercapacitors. The operation of a Hybrid Bus is taken as a case study in order to evaluate the effects of battery lifetime models’ accuracy on ESS sizing and operation in a heavy-duty application. For this purpose, two different lifetime models (a Wöhler-curve-based model and a semi-empirical model) were applied in the multi-objective optimisation of a hybrid electric urban bus. Differences up to ca. 8% on the daily operation costs and ca. 25% on the dual ESS costs were estimated depending on the lifetime model considered for the optimisation.
Analysis of in Vitro and in Vivo Characteristics of Human Embryonic Stem Cell-Derived Neural Precursors
Authors: Kozubenko Nataliya , Turnovcova Karolina , Kapcalova Miroslava , Butenko Olena , Anderova Miroslava , Rusnakova Vendula , Kubista Mikael , Hampl Ales , Jendelova Pavla , Sykova Eva
Published: July 2018

During the last decade, much progress has been made in developing protocols for the differentiation of human embryonic stem cells (hESCs) into a neural phenotype. The appropriate agent for cell therapy is neural precursors (NPs). Here, we demonstrate the derivation of highly enriched and expandable populations of proliferating NPs from the CCTL14 line of hESCs. These NPs could differentiate in vitro into functionally active neurons, as confirmed by immunohistochemical staining and electrophysiological analysis. Neural cells differentiated in vitro from hESCs exhibit broad cellular heterogeneity with respect to developmental stage and lineage specification. To analyze the population of the derived NPs, we used fluorescence-activated cell sorting (FACS) and characterized the expression of several pluripotent and neural markers, such as Nanog, SSEA-4, SSEA-1, TRA-1-60, CD24, CD133, CD56 (NCAM), β-III-tubulin, NF70, nestin, CD271 (NGFR), CD29, CD73, and CD105 during long-term propagation. The analyzed cells were used for transplantation into the injured rodent brain; the tumorigenicity of the transplanted cells was apparently eliminated following long-term culture. These results complete the characterization of the CCTL14 line of hESCs and provide a framework for developing cell selection strategies for neural cell-based therapies.
Buildup of Abiotic Oxygen and Ozone in Moist Atmospheres of Temperate Terrestrial Exoplanets and Its Impact on the Spectral Fingerprint in Transit Observations
Authors: Kleinböhl Armin , Willacy Karen , Friedson A. James , Chen Pin , Swain Mark R.
Published: July 2018

We investigate the abiotic production of oxygen and its photochemical byproduct ozone through water vapor photolysis in moist atmospheres of temperate terrestrial exoplanets. The amount of water vapor available for photolysis in the middle atmosphere of a planet can be limited by an atmospheric cold-trap, the formation of which largely depends on the amount of noncondensable gases. We study this effect using a photochemical model coupled to a 1D radiative-convective equilibrium model in atmospheres with N2, CO2, and H2O as the main constituents. We find that in atmospheres with a low N2 inventory, water vapor mixing ratios in the middle atmosphere can be more than two orders of magnitude higher compared to atmospheres with an Earth-like N2 inventory. Without a strong surface sink, the noncondensable oxygen can build up rapidly, drying out the upper atmosphere. With a moderate surface sink, the planet can approach a steady state with significant oxygen mixing ratios in which oxygen production is balanced by surface uptake. We use a radiative transfer model to study the spectroscopic fingerprint of these atmospheres in transit observations. Spectral signatures of abiotic oxygen and ozone can be of comparable magnitude as in spectra of Earth seen as an exoplanet. Middle atmospheric water vapor is unlikely to be a usable indicator of the abiotic origin of oxygen because of the influence of oxygen on the water vapor distribution. This suggests that atmospheric oxygen and ozone cannot be used as binary bioindicators and that their interpretation will likely require atmospheric and planetary models.
Suppression of Coronal Mass Ejections in Active Stars by an Overlying Large-scale Magnetic Field: A Numerical Study
Authors: Alvarado-Gómez Julián D. , Drake Jeremy J. , Cohen Ofer , Moschou Sofia P. , Garraffo Cecilia
Published: July 2018

We present results from a set of numerical simulations aimed at exploring the mechanism of coronal mass ejection (CME) suppression in active stars by an overlying large-scale magnetic field. We use a state-of-the-art 3D magnetohydrodynamic code that considers a self-consistent coupling between an Alfvén wave-driven stellar wind solution, and a first-principles CME model based on the eruption of a flux rope anchored to a mixed-polarity region. By replicating the driving conditions used in simulations of strong solar CMEs, we show that a large-scale dipolar magnetic field of 75 G is able to fully confine eruptions within the stellar corona. Our simulations also consider CMEs exceeding the magnetic energy used in solar studies, which are able to escape the large-scale magnetic field confinement. The analysis includes a qualitative and quantitative description of the simulated CMEs and their dynamics, which reveals a drastic reduction of the radial speed caused by the overlying magnetic field. With the aid of recent observational studies, we place our numerical results in the context of solar and stellar flaring events. In this way, we find that this particular large-scale magnetic field configuration establishes a suppression threshold around ∼3 × 1032 erg in the CME kinetic energy. Extending the solar flare-CME relations to other stars, such CME kinetic energies could be typically achieved during erupting flaring events with total energies larger than 6 × 1032 erg (GOES class ∼X70).
Neutron Star Equation of State from the Quark Level in Light of GW170817
Authors: Zhu Zhen-Yu , Zhou En-Ping , Li Ang
Published: July 2018

The matter state inside neutron stars (NSs) is an exciting problem in astrophysics, nuclear physics, and particle physics. The equation of state (EOS) of NSs plays a crucial role in the present multimessenger astronomy, especially after the event of GW170817. We propose a new NS EOS, “QMF18,” from the quark level, which describes robust observational constraints from a free-space nucleon, nuclear matter saturation, heavy pulsar measurements, and the tidal deformability of the very recent GW170817 observation. For this purpose, we employ the quark mean-field model, which allows us to tune the density dependence of the symmetry energy and effectively study its correlations with the Love number and the tidal deformability. We provide tabulated data for the new EOS and compare it with other recent EOSs from various many-body frameworks.
The effect of curing hepatitis C with direct-acting antiviral treatment on endothelial function
Authors: Davis Joshua S , Young Melissa , Lennox Sandra , Jones Tracey , Piera Kim , Pickles Robert , Oakley Stephen
Published: July 2018

Background

Epidemiological data suggest that chronic HCV infection (CHC) is associated with increased cardiovascular risk, but it is unknown if it is associated with endothelial dysfunction. We aimed to assess the effect of antiviral treatment on endothelial function in non-cirrhotic adults with CHC.

Methods

Self-controlled before and after study. All patients had genotype-1 CHC and were treated with 12 weeks of paritaprevir/ritonavir, ombitasvir and dasabuvir (PrOD), with ribavirin added for those with geno-type-1a infection. Endothelial function was assessed at three time points before antiviral treatment, at treatment weeks 1, 4, 8 and 12, and 12 weeks after the end of treatment. The main assessment tools were reactive hyperaemia peripheral arterial tonometry (RHPAT) and serum concentrations of angiopoietin-2 (Ang-2) and E-selectin.

Results

A total of 16 patients were enrolled. Mean (sd) age was 51.4 (6.9) years and 11 participants (69%) were male. All 16 patients achieved a sustained virological response. The mean (sd) baseline RHPAT index was 2.05 (0.48), and there was no significant change during treatment (mean within-patient change from baseline to end of treatment =-0.23 [0.45]; P= not significant). There was a significant improvement in both mean Ang-2 (baseline 2.44 [0.79] ng/ml, within-patient change -0.60 [0.44]; P<0.001) and E-selectin (baseline 48.7 [21.5] ng/ml, within-patient change -14.4 [13.0]; P<0.001).

Conclusions

Removing HCV viraemia is associated with a significant improvement in endothelial function as measured by serum markers, but not in bedside micro-vascular reactivity. Chronic HCV viraemia may be associated with endothelial cell dysfunction and therefore long-term cardiovascular risk.
Morphology and molecular genetics reveal two new Leptobrachella species in southern China (Anura, Megophryidae)
Authors: Wang Jian , Yang Jianhuan , Li Yao , Lyu Zhitong , Zeng Zhaochi , Liu Zuyao , Ye Youhua , Wang Yingyong
Published: July 2018

Based on morphological and phylogenetic analyses (16S rRNA mtDNA), two new species of the genusLeptobrachellaare described from southern China, namelyL.yunkaiensisWang, Li, Lyu & Wang,sp. n.from Dawuling Forest Station of Guangdong Province andL.wuhuangmontisWang, Yang & Wang,sp. n.from Mt. Wuhuang of Guangxi Province. To date, the genusLeptobrachellacontains 68 species, among which 13 species are known from China. The descriptions of the two new species further emphasize that the species diversity of the genusLeptobrachellafrom China is still highly underestimated and requires further investigations.
Ecto- and endo-parasitic monogeneans (Platyhelminthes) on cultured freshwater exotic fish species in the state of Morelos, South-Central Mexico
Authors: Mendoza-Franco Edgar F. , Caspeta-Mandujano Juan Manuel , Tapia Osorio Marina
Published: July 2018

An extensive parasitological study of 365 freshwater exotic fish specimens belonging to 13 species of seven families (Cichlidae, Cyprinidae, Osphronemidae, Pangasidae, Poeciliidae, Characidae, and Loricariidae) collected from 31 Aquaculture Production Units (APU) from Central Mexico revealed the occurrence of 29 ecto- and endo-parasitic monogeneans found on gills and stomachs: Cichlidogyrussclerosus, C.thurstonae, C.tilapiae, Cichlidogyrus sp. 1, Cichlidogyrus sp. 2, Enterogyruscoronatus, E.malmbergi, Gusseviaspiralocirra, Sciadicleithrumiphthimum, Sciadicleithrum sp., Scutogyruslongicornis (all Dactylogyridae), Gyrodactyluscichlidarum, and G.yacatli (Gyrodactylidae) on Oreochromisniloticus, Pterophyllumscalare and Hemichromis sp. (Cichlidae); Dactylogyrusbaueri, D.formosus, D.intermedius, D.vastator, D.extensus, Dactylogyrus sp. (all Dactylogyridae), and G.kobayashii on Carassiusauratus, Cyprinuscarpio and Ctenopharyngodonidella (Cyprinidae); Trianchoratusacleithrium and T.trichogasterium (Dactylogyridae) on Trichogastertrichopterus (Osphronemidae); Thaparocleiduscaecus, T.siamensis (Dactylogyridae), and Dactylogyridae sp. on Pangasianodonhypophthalmus (Pangasidae); G.poeciliae on Poeciliareticulata (Poeciliidae); Diaphorocleidusarmillatus (Dactylogyridae) on Gymnocorymbusternetzy (Characidae); Unilatusunilatus (Dactylogyridae) and Gyrodactylidae sp. on Hypostomus sp. (Loricariidae). The paramount importance of the establishment of these monogeneans due to the importation/exportation of non-native ornamental and other exotic host fish species cultured for food in Mexico is briefly discussed. Quarantine is recommended for all transferred host species.
Employés publics dans les environnements hybrides : quelles ancres d’engagement et quelles pratiques de GRH ?
Authors: Kouadio Armand Brice , Emery Yves
Published: July 2018

Mobilisant une approche exploratoire, nous analysons les ancres d’engagement au travail chez les agents publics œuvrant dans des contextes post-bureaucratiques. La notion d’Engagement au travail élargit le concept d’engagement organisationnel (Organizational Commitment) à des conditions et réalités professionnelles non exclusivement liées aux organisations et présentant des caractéristiques hybrides. Cette recherche permet d’identifier quelles ancres d’engagement sont dominantes et typiques des environnements publics post-bureaucratiques, à côté des ancres classiques identifiées dans la littérature (organisation, équipe de travail, superviseur, emploi, profession), tout en analysant leurs implications en termes de GRH publique. En mobilisant un cadre analytique basé sur les ancrages multiples de la relation au travail, cette étude permet une compréhension plus fine de l’engagement au travail des agents publics Suisses.
Entre communautés de pratique et communautés épistémiques : l’émergence de communautés hybrides dans les espaces urbains
Authors: Evrard Samuel Karine , Carré Maxime
Published: July 2018

Des communautés se forment progressivement dans de nombreuses villes françaises autour des questions de logistique urbaine. En effet, les flux de marchandises dans les espaces urbains se sont accrus de manière rapide ces dernières années et génèrent des défis environnementaux et sociétaux importants, impliquant une multitude de parties prenantes qui doivent collaborer. Notre objectif dans cet article est d’analyser en quoi la notion de communauté permet d’éclairer l’organisation singulière de la collaboration entre acteurs privés et publics dans les espaces urbains. La méthodologie de la recherche s’appuie sur une recherche longitudinale menée sur une communauté en construction dans l’agglomération grenobloise. Nous illustrons les étapes de la démarche, et mettons en évidence que le processus de construction de la communauté est caractérisé par une intensification des échanges entre ces acteurs, l’établissement de règles de communication et l’émergence de plusieurs projets en parallèle. Nos résultats permettent de définir les contours d’une nouvelle forme de communauté que nous qualifions d’ hybride , croisant à la fois les caractéristiques des communautés de pratiques et des communautés épistémiques. Nous éclairons les éléments qui contribuent au succès de cette communauté, mais également les freins à son développement, à son maintien et à la réalisation d’actions par les membres de la communauté. Cette recherche permet de faire émerger un nouvel objet organisationnel qui rompt avec les codes traditionnels des communautés de pratique. La gouvernance des espaces urbains mêlant acteurs privés et publics peut ainsi être éclairée sous un nouvel angle novateur dans le cadre de l’étude des territoires et des collectivités.
Unpacking Complexities of Mega-Scale Public Sector Information Technology Projects: An Ecosystem Perspective
Authors: Fagnot Isabelle , Ye Chen , Desouza Kevin C.
Published: July 2018

Les projets de technologies de l’information (TI) à grande échelle dans le secteur public sont des entreprises importantes qui opèrent dans un écosystème d’intervenants, de ressources et de contraintes. En utilisant le concept d’écosystème, ce projet de recherche étudie trois projets TI à grande échelle dans le secteur public qui ont échoué : le U.S. Federal Bureau of Investigation’s (FBI) Virtual Case File (VCF), le projet U.S. federal government’s HealthCare.gov et le projet britannique National Programme for IT (NPfIT). Une analyse de ces projets a été réalisée à l’aide de la méthodologie Analyse Qualitative Média (QMA). Les résultats suggèrent que plusieurs parties prenantes dans un grand projet public TI assument des rôles analogues à différents types d’espèces dans un écosystème avec l’agence publique soutenant le projet dans en tant qu’espèce clé. Plus précisément, les résultats montrent que l’agence publique est susceptible de ne pas embaucher du personnel clé ayant les connaissances et l’expérience appropriées, et de ne pas réagir aux signaux précoces alertant sur l’imminence de l’implosion de l’écosystème du projet. De plus, les failles dans les relations entre l’organisme public et les entrepreneurs sous contrat et dans les relations entre la législature et l’organisme public contribuent également de façon importante à l’échec du projet.
Development of causal model of sustainable hospital supply chain management using the Intuitionistic Fuzzy Cognitive Map (IFCM) method
Authors: Mirghafoori Seyed Habibollah , Morovati Sharifabadi Ali , Karimi Takalo Salim
Published: July 2018

Purpose: Service industry is a massive sector accounting for about two-thirds of GDP of developed economies and is the field of an intensive competition between service companies and their supply chains. As a result, service supply chain management has become a subject of growing interest to researchers and business analysts. Healthcare industry is among the largest service industries with the highest potential for improvement in sustainability performance. The purpose of this study was to identify the concepts influencing the sustainability of hospital supply chain and provide a causal model for sustainable supply chain of hospital service.Design/methodology/approach: In this study, concepts that influence the sustainability of a hospital service supply chain were identified by in-depth interviewing of 18 experts in hospitals of Kerman, Iran. Delphi method was used to reorganize the initial concepts into 15 concepts. Finally, the Intuitionistic Fuzzy Cognitive Map (IFCM) method was used to develop the causal model of sustainable supply chain management for hospital service.Findings: Delphi method was used to reorganize 68 initial concepts into 15 concepts Contains: demand management, resource and capacity management, customer relationship management, supplier relationship management, service management, information management, financial performance management, Attention to the environment, contamination, energy consumption, legal requirements, employees, community and stakeholders, social accountability and business ethics. The results indicate that service delivery management is highly central among other concepts.Originality/value: with focusing on concepts such as service management, and capacity and resources management, The sustainability of the hospital supply chain can be improved.
Mobile Assessment Procedures for Mental Health and Literacy Skills in Education
Authors: Stathopoulou Agathi , Karabatzaki Zoe , Kokkalia Georgia , Dimitriou Eleni , Loukeri Paraskevi Ioanna , Economou Alexandra , Drigas Athanasios
Published: July 2018

Mobile technology seems crucial for learning and teaching as it plays an important role in student’s social, emotional and academic life. This paper examines its role in secondary education focusing in mobile applications that support literacy and mental health in students. The results of a research that investigated the relationship between performance in language of secondary school pupils and the occurrence of depression symptoms are presented.
Microstructure Evolution and Mechanical Behavior in Shape Memory Nanostructured TiNi Alloy
Authors: Misochenko Anna , Tilak Kumar Jeevanandham Vijaya , Jayaprakasam Sudha , Padmanabhan K. Anantha , Stolyarov Vladimir
Published: July 2018

Influence of grain size on the martensitic transformation and mechanical properties of shape memory alloy Тi49.3Ni50.7 was studied. The features of the mechanical response of coarse-grained and nanostructured alloys were identified. The microstructure investigations involved the use of TEM and SEM.
Atomic Force Microscopy Studies of Severely Deformed Amorphous TiNiCu Alloy
Authors: Gunderov Dmitriy , Boltynjuk Evgeniy , Ubyivovk Evgeniy , Lukyanov Alexander , Churakova Anna , Zamula Yuri , Batyrshin Eduard , Kilmametov Askar , Valiev Ruslan Z.
Published: July 2018

The amorphous Ti50Ni25Cu25 alloy was subjected to high pressure torsion (HPT) processing. TEM studies revealed in the structure of the HPT-processed samples the presence of nanocrystals with a size of about 5 nm and amorphous clusters with a size of about 10-30 nm. Atomic force microscopy (AFM) was used to study the surface morphology of foils prepared by ion polishing from the initial amorphous ribbons and HPT-processed samples. AFM images of the foil prepared from the initial ribbon revealed a smooth surface with an average roughness of 0.3 nm. A totally different surface morphology was observed for the foil prepared from the HPT-processed state by the same regime of ion polishing: the presence of holes with a depth of 2-4 nm and a width of 10-30 nm. The changes in the surface morphology, namely the holes-like surface morphology of the HPT-processed state, could be explained by a complex transformation of the amorphous structure, and probably by the variation and redistribution of free volume, which leads to the emergence of a cluster contrast in TEM images.
In Situ Observation of the Phase Transformations in Ti15Mo Alloy Deformed by High Pressure Torsion
Authors: Janeček Miloš , Bartha Kristina , Stráský Josef , Veselý Jozef , Polyakova Veronika , Semenova Irina
Published: July 2018

Metastable β-Ti alloys including Ti15Mo alloy are perspective candidates for use in medical applications. During thermal treatment Ti15Mo alloy undergoes various phase transformations. After solution treatment it contains metastable β-phase and ω-phase. During annealing the ω-phase partially dissolves as well as stable α-phase particles are formed. The solution treated Ti15Mo alloy was deformed by high pressure torsion (HPT) at room temperature. Significant grain refinement with grain size of ~100 nm was achieved even after 1/4 of HPT rotation. The effect of the ultra-fine grained (UFG) structure achieved by HPT on the phase transformations was studied by differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) during in-situ heating. High density of lattice defects, dense network of grain boundaries as well as ongoing recovery and recrystallization upon heating significantly affected the phase transitions. Observation of the microstructure during in-situ heating in TEM revealed no representative changes in transparent part of the sample due to the “thin foil effect”.
Mechanical Behavior of Twinning Induced Plasticity Steel Processed by Warm Forging and Annealing
Authors: Wang Wen , Wang Dan , Han Fu Sheng
Published: July 2018

The present study shows that warmly forged and low-temperature annealed twinning induced plasticity (TWIP) steel exhibited very high dislocation density and apparent yield-point phenomenon in addition to very high yield strength. The initial density of dislocations significantly affected the evolution of dislocations during the subsequent tensile deformation. Original high dense dislocations prompted the rapid increase of dislocations, and intensified the complexity of dislocation configurations. All these effects made the twinning deformation weakened but the dislocation deformation enhanced, leading to increased strength but decreased plasticity.
The Effect of Ultrafine-Grained Structure of Al-30Zn on the Shape Forming Ability at Sheet Metal Forming
Authors: Bobruk Elena V. , Tyulenev Denis G. , Golubev Oleg V. , Murashkin Maxim Y.
Published: July 2018

High pressure torsion (HPT) and equal channel angular pressing in parallel channels (ECAP-PC) at room temperature are used to form homogeneous ultrafine-grained (UFG) structure with a grain size of the aluminum matrix of 350 and 700 nm, respectively, in Al-30Zn (wt. %) specimens. The UFG samples with special geometry produced from the specimens processed by SPD techniques were subjected to sphere-shaped dimple extrusion testing (via the Erikson test method) and bended plate extrusion to determine the material formability during cold sheet metal forming. The same tests were performed on the material with coarse-grained (CG) structure for the sake of comparison. The obtained results are discussed.
Variability of Twin Boundary Structure in Computer Simulations of Tensile Twins in Magnesium
Authors: Kushnir Kostianyn , Ostapovets Andriy
Published: July 2018

Variety of interatomic potentials for magnesium can be found in the literature. Result of computer simulations can be slightly different depending on used potential. Particularly, twin boundary structure with the lowest energy can be different in a frame of different models. Comparison of several popular embedded-atom method potentials is provided. It is shown that either reflection or glide structure of twin boundary has the lowest energy for different potentials.
Analytical Modeling of Strength and Electrical Conductivity of Nanostructured Cu-Cr Alloys
Authors: Chembarisova Roza G. , Alexandrov Igor V. , Wei Wei
Published: July 2018

The analysis of the strength characteristics and electrical conductivity of annealed Cu-1.0wt.%Cr-0.1wt%Zr alloy subjected to subsequent deformation under various conditions was carried out by analytical modeling methods. The contributions of the regions with nanotwins, as well as such defects of the crystal structure as vacancies, alloying atoms, dislocations, and particles of the secondary phase to the strength and electrical conductivity of the material were estimated.
Influence of High Pressure Torsion on Thermoelastic and Thermoelectric Response of Pure Copper and Aluminum under Pulsed Laser Radiation
Authors: Smirnov Ivan V. , Sudenkov Yuri V.
Published: July 2018

This work presents experimental studying the effect of processing by severe plastic deformation (SPD) on the thermoelastic and thermoelectric properties of pure aluminum and copper under pulsed laser radiation. The studies were carried out on technical aluminum AD1 (99.3%) and pure copper M1 (99.9%). High pressure torsion (HPT) was used for processing by SPD. After the HPT processing, the materials samples in the form of a plane disk were subjected to pulsed laser radiation focused on the disk center. Pulsed lasers with a wavelength of 1.06 micron and operating in the free laser oscillation mode with pulse duration of 100 microseconds or in the mode of a single pulse with duration of about 10 nanoseconds were used. The thermoelastic and thermoelectric responses of the materials were determined by measuring acoustic waves and the thermoelectric power. The disks with the initial coarse-grained material state were considered as a reference sample, and the disks of the materials after SPD processing were considered as a controlled object. The results demonstrated a very high sensitivity of the parameters of thermoelastic and thermoelectric response to structural changes in the materials. For example, the used HPT mode led to a reduction in the maximum thermoelectric power value for aluminum by 40% and for copper by 35%.
Multiple Shear Bands in Zr-Based Bulk Metallic Glass Processed by Severe Plastic Deformation
Authors: Boltynjuk Evgeniy , Ubyivovk Evgeniy , Gunderov Dmitriy , Mikhalovskii Vladimir , Valiev Ruslan Z.
Published: July 2018

The Zr62Cu22Al10Fe5Dy1 bulk metallic glass was subjected to high pressure torsion (HPT) processing at temperatures of 20 and 150°C. Structural studies were carried out by TEM on the lamella-sample prepared from the HPT-specimens in transversal direction to the specimen plane. TEM studies revealed formation of multiple shear bands with spacings in a 20-50 nm range for both HPT states. Shear bands could be divided in two types: primary and secondary bands. The morphology of shear bands strongly depends on the processing temperature. Shear bands are distributed homogeneously throughout the whole lamella-sample for state processed by HPT at temperature of 20°C. Regions with shear bands are divided by amorphous regions on lamella-sample cut from the sample processed by HPT at temperature of 150°C. Analysis of optical microscopy and SEM data showed that shear bands are distributed throughout the whole volume of HPT-specimens.
Mesoscopic Scale Modeling of "Superplastic" Flow in Geological and Glacial Materials
Authors: Basariya M. Ravithul , Padmanabhan K. Anantha
Published: July 2018

A viewpoint that suggests that grain/ interphase boundary sliding (GBS) that develops to a mesoscopic scale (“cooperative boundary sliding”) controls optimal superplastic (SP) deformation is able to explain superplasticity in metals and alloys, ceramics, intermetallics, composites and bulk metallic glasses of grain sizes ranging from a few microns down to a few nanometers. It is extended here to describe grain-size-sensitive (GSS) flow in minerals, rocks and ice within narrow experimental ranges. In this approach the accommodation processes of grain boundary diffusion, dislocation emission from sliding boundaries and/ or grain rotation accompanying boundary sliding are present overextremely short distancesand are assumed to be faster than GBS. Analysis shows that GSS creep in geological and glacial materials can be accounted for in terms of four “universal”, mesoscopic scale constants of average values, = 0.197, = 0.415 J.m-2, = 8.9 and = 0.166, where is the average shear strain associated with a basic boundary sliding event at the level of the atomistics, is the specific grain boundary energy (assumed to be isotropic), is the number of boundaries that align to form a mesoscopic boundary glide plane and “” is a constant that obeys the condition 0<a<0.5, whose magnitude depends on grain shape and size distribution in the material. It is demonstrated that with the help of these four constants and the Frost-Ashby equations for estimating the shear modulus, it is possible to predict steady state GSS creep flow in any geological or glacial material, including those whose mechanical response was not used to obtain the “universal” constants. Whether these observations are evidence for “superplasticity” in these materials can be known only if the findings are reproduced in tensile deformation also.
Mechanical Behavior of Ti-6Al-2Sn-4Zr-2Mo Titanium Alloy under Hot and Superplastic Forming Conditions: Experiment and Modeling
Authors: Yamane Gen , Velay Vincent , Vidal Vanessa , Matsumoto Hiroaki
Published: July 2018

Titanium alloys are widely used in the aircraft industry. Under sheets form, they can be employed to the manufacturing of pylon or engine parts. With the aim of a cost reduction, this study proposes to act on the starting microstructure so as to improve the mechanical properties during the forming stages. In the present study, investigations are focused on Ti-6Al-2Sn-4Zr-2Mo (Ti6242) alloy specially used for the hot areas (e.g. parts close to the engine or the combustion chambe...). Presently, an important mechanical test campaign was performed on Ti6242 alloy, it examines, on the one hand, the microstructure qualified by the aircraft industry and, on the other hand, a new range of refined microstructures obtained by hot straining process. For each test, microstructural observations exhibited complex phenomena including simultaneously both grain growth and dynamic recrystallization. The occurrence, sequencing and coupling of the mechanisms, strongly depend on the starting microstructure and the test conditions (time-temperature and strain rate) investigated. They are not easy to understand and require further tests and observations. In such a framework, the implementation of mechanical models are efficient and relevant to promote a better knowledge of the microstructural evolution observed and their influence on the mechanical behavior.
Studies on Titanium Alloys for Aerospace Application
Authors: Gomez-Gallegos Ares , Mandal Paranjayee , Gonzalez Diego , Zuelli Nicola , Blackwell Paul
Published: July 2018

Since the development of the Ti54M titanium alloy in 2003, its application within the aerospace sector has gradually increased due to the combination of properties such as improved forgeability and machinability, low flow stress at elevated temperatures, and superplastic characteristics. However, for the successful exploitation of Ti54M a comprehensive understanding of its mechanical characteristics, microstructure stability, and superplastic behaviour is required. The superplastic forming of titanium alloys is characterised by high deformation at slow strain rates and high temperatures which influence the material microstructure, and in turn, determine the forming parameters. These mechanisms make the prediction of the material behaviour very challenging, limiting its application within the aerospace industry. Even though Ti54M has been commercially available for over 10 years, further studies of its mechanical and superplastic properties are still required with the aim of assessing its applicability within the aerospace industry as a replacement for other commercial titanium alloys. Therefore, in this work a study of the mechanical and superplastic properties of Ti54M, in comparison with other commercial titanium alloys used in the aerospace industry - i.e. Ti-6AL-4V, and Ti-6-2-4-2 - is presented. The final objective of this study, carried out at the Advanced Forming Research Centre (AFRC, University of Strathclyde, UK), is to obtain material data to calibrate and validate a model capable of estimating the behaviour and grain size evolution of titanium alloys at superplastic conditions.
Research on Quick Superplastic Forming Technology of Industrial Aluminum Alloys for Rail Traffic
Authors: Wang Guo Feng , Jia Hui Hui , Gu Yi Bin , Liu Qing
Published: July 2018

Quick superplastic forming is a new technology, which combines hot drawing preforming and superplastic forming. It makes full use of the high speed of hot drawing and good formability of superplasticity. For aluminum alloy complex components, the difficulties of stamping and low speed of superplasticity be perfect solved. In this work, the best forming process of side wall outer panel of metro vehicle was determined by forming experiment using quick superplastic forming technology. The high-speed rail edge skin with a very small fillet shape (R≤4 mm) and the large-size subway door frame part (h≈80 mm) formed by straight wall deep drawing were manufactured, using industrial aluminum alloy sheet with thickness of 4 mm. Meanwhile, the formed parts show the advantages of high dimensional accuracy and uniform wall thickness distribution, and the mechanical properties of formed parts can completely meet the requirements as well, which demonstrates the desirable efficiency, low cost and feasibility of this new technology.
Low Temperature Superplasticity in Ultrafine-Grained AZ31 Alloy
Authors: Figueiredo Roberto B. , Pereira Pedro Henrique R. , Langdon Terence G.
Published: July 2018

The mechanical behavior of an AZ31 magnesium alloy processed by high-pressure torsion (HPT) was evaluated by tensile testing from room temperature up to 473 K at strain rates between 10-5 – 10-2 s-1. Samples tested at room temperature and at high strain rates at 373 K failed without any plastic deformation. However, significant ductility, with elongations larger than 200%, was observed at 423 K and 473 K and at low strain rates at 373 K. The high elongations are attributed to a pronounced strain hardening and a high strain rate sensitivity. The results agree with reports for a similar alloy processed by severe plastic deformation. However, the level of flow stress is lower and the strain rate sensitivity and the elongations are larger than observed in this alloy processed by conventional thermo-mechanical processing.
Superplastic Flow and Micro-Mechanical Response of Ultrafine-Grained Materials
Authors: Kawasaki Megumi , Jang Jae Il , Langdon Terence G.
Published: July 2018

The bulk ultrafine-grained (UFG) materials usually show superior mechanical properties. Since the occurrence of superplastic flow generally requires a grain size smaller than ~10 μm, it is anticipated that materials processed by severe plastic deformation (SPD) will exhibit superplastic ductilities when pulled in tension at elevated temperatures. Recent advances in the processing of UFG metals have provided an opportunity to extend the understanding of superplastic flow behavior to include UFG materials with submicrometer grain sizes. Recent studies showed the UFG materials demonstrated the development of plasticity in micro-mechanical response at room temperature by the significant changes in microstructure attributed to high-pressure torsion (HPT). Accordingly, this study summarizes recent results on excellent ductility and plasticity in a UFG Zn-22% Al alloy. Specifically, the alloy demonstrated the occurrence of exceptional superplastic flow at high temperature after equal-channel angular pressing and HPT and excellent room temperature plasticity of the alloy after HPT where the plasticity was evaluated by the nanoindentation technique. The significance of purity of the alloy is also considered for enhancing the ductility at room temperature.
Poly(Lactic Acid)/Poly(Vinyl Alcohol)/Graphene Nanocomposites
Authors: Rattanakot Jalupak , Potiyaraj Pranut
Published: July 2018

Poly(lactic acid) (PLA) is an interesting material as an environmentally-friendly replacement of petroleum-based polymers. However, some properties need improvements in order to commercially utilized PLA. In this work, graphene is used as a reinforcing filler and poly(vinyl alcohol) is used as a carrier to enhance dispersion of graphene in PLA matrix. The addition of graphene aims at improving the mechanical and thermal properties of PLA. The functional groups of graphene were characterized by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The mechanical property testing was performed using a universal testing machine. The thermal properties were measured through differential scanning calorimetry (DSC). As a result, the Young’s modulus and the thermal properties of PLA composites increased as the amount of graphene in the composites increased due to improved dispersion of graphene in PLA matrix.
Effect of the Size of Molten Carbonate Fuel Cells on the Temperature Distribution
Authors: Lee Chang Whan , Yu Jae Hyeong , Kim Hyun Woo , Ryu Bo Hyun
Published: July 2018

Molten carbonate fuel cells (MCFCs) are high-temperature fuel cells that use liquid electrolytes composed of molten carbonates such as Li2CO3, Na2CO3, and K2CO3. Electrochemical reactions of MCFCs are exothermic reaction. Consequently, temperature distribution of fuel cells is one of important factors in long-term operation. In this work, the effects of the size of the fuel cell on the temperature distribution were investigated using CFD analysis. It was found that as the length of the gas flow direction and the number of layers of fuel cell increases, the maximum temperature of the cell was increased.
Preparation and Properties of Poly(Lactic Acid)/Epoxidized Natural Rubber/Nano-Silica Composites
Authors: Mongkolvai Auttapol , Chuayjuljit Saowaroj , Chaiwutthinan Phasawat , Larpkasemsuk Amnouy , Boonmahitthisud Anyaporn
Published: July 2018

This study aimed to improve the toughness property of poly(lactic acid) (PLA) by incorporating epoxidized natural rubber (ENR), an elastomeric material and silica nanoparticle (nSiO2), a spherical inorganic nanofiller. ENR with 30mol% epoxidation (ENR 30) was first prepared via in situ epoxidation of natural rubber by performic acid generated from the reaction between formic acid and hydrogen peroxide in the latex stage. The PLA was melt blended with three weight percentages (10, 20 and 30wt%) of ENR in an internal mixer, followed by a compression molding. The effects of ENR loadings on the mechanical properties and thermal stability of the blends were first investigated. It was found that the addition of ENR 30 increased the toughness property of the blends. The blend at 20wt% ENR 30 exhibited the highest impact strength and elongation at break, and so was selected for preparing nanocomposites with three loadings (1, 2 and 3 parts per hundred of resins) of nano-silica (nSiO2). The results showed that all PLA/ENR 30/nSiO2 nanocomposites exhibited higher impact strength and thermal stability than the neat 80/20 PLA/ENR 30 blend.