bluuebunny/crossref_metadata_2025_split huggingface dataset:
Combinación de fibras de acero de última generación para el refuerzo de hormigón autocompactante
Authors: Galvez Jaime , Alberti Marcos G. , Enfedaque Alejandro , Cortez Adriana 
Published: March 2018

En las últimas décadas, el hormigón reforzado con fibras (HRF) ha avanzado hacia aplicaciones estructurales, permitiendo la sustitución del refuerzo con barras corrugadas por fibras, especialmente de acero [1, 2]. Para la utilización estructural del hormigón reforzado con fibras se utilizan normalmente valores de resistencia a la tracción por flexión, tal y como refleja la normativa existente de referencia [3, 4]. Los resultados de estos ensayos están fuertemente influidos por la orientación y distribución de las fibras en la superficie de fractura, por lo que la combinación del HRF con hormigón autocompactante (HAC) mejora los resultados de fractura en dicha dirección gracias a la orientación preferente que toman las fibras en la dirección del flujo de hormigonado [5, 6]. El hormigón reforzado con fibras de acero (HRFA) permite además el uso de fibras con los extremos formando patillas que, junto con un alto módulo de elasticidad, facilitan la obtención de resultados aptos para piezas estructurales [7, 8]. No obstante, la aportación durante el amasado de altos contenidos de fibras rígidas provoca una disminución de la trabajabilidad y no permite la obtención sencilla de un hormigón que mantenga las propiedades autcompactantes en estado fresco [9]. Por otro lado, las sinergias encontradas combinando distintas tecnologías de hormigón también se han encontrado combinando tipologías de fibras diferentes [10], lo que abre un importante abanico de posibilidades como la combinación de fibras con distinta longitud.En esta investigación se presentan los resultados de un trabajo experimental con el objetivo de optimizar los procesos de diseño de HAC reforzado con fibras de acero para obtener mezclas robustas con alta resistencia y manteniendo sus propiedades en estado fresco. Se realizó una campaña experimental en la que se elaboró un HAC sin fibras de referencia (H0) al que después se añadieron 70kg/m3 de fibras de acero (H70). Además se combinaron por igual dos tipos de fibras de acero con un contenido total de 70kg/m3 (H70M). Con estas 3 mezclas se estudió la influencia de la incorporación de altos contenidos y tipos de fibras de acero en las propiedades en estado fresco del hormigón autocompactante. Posteriormente se caracterizaron las propiedades mecánicas y en fractura de los hormigones fabricados obteniendo resultados que mostraron las sinergias en la utilización de dos tipologías de fibras.DOI: http://dx.doi.org/10.4995/HAC2018.2018.5152
Influência da adição de fibras metálicas em concreto autoadensável no estado endurecido
Authors: Silva Gisele , Cristofoli Tiago , Tutikian Bernardo , Christ Roberto 
Published: March 2018

A utilização do concreto autoadensável reforçado com fibras permite um grande avanço nas propriedades do concreto convencional. As fibras são adicionadas à mistura com a finalidade de melhorar suas propriedades mecânicas no estado endurecido, aliadas às características de alta trabalhabilidade e sem segregação, quando no estado fresco. Este compósito apresenta uma dispersão mais uniforme das fibras dentro dos elementos estruturais, graças à eliminação de compactação e vibrações, visto que as vibrações tendem a causar a segregação das fibras. Assim, podem ser executados elementos estruturais de espessuras reduzidas com alta qualidade, majorando sua resistência à tração na flexão e suavizando a curva de tensão-deformação, quando comparados ao concreto sem incorporação de fibras. Ainda, pode aumentar a segurança com a prevenção de fissuras e o aumento da tenacidade do concreto. Os tipos de fibras comumente utilizadas são de origem metálica, constituídas de aço carbono e sintéticas, com variações de polímeros inorgânicos. Elas exercem diferente influência no comportamento do material. De modo a verificar a influência da utilização da adição de fibras nas propriedades do material, foi dosado um traço de concreto autoadensável, com fibras de aço de três fatores de forma, nas porcentagens de 0,25%, 0,5% e 1,0% em relação ao volume total do material. Após a avaliação dos resultados foi possível afirmar que a mistura testada com melhores resultados possui uma taxa de 1,0% da fibra com maior fator de forma. Apresentou perda de apenas 9,1% na resistência à compressão, aumento de 261% da resistência à tração na flexão e mais de 31 vezes o acréscimo do valor de fator de tenacidade em relação à mistura referência. Este estudo mostra que o concreto autoadensável com a incorporação de fibras metálicas tem aplicabilidade em situações onde é necessária elevada resistência a esforços de tração e elevada tenacidade, podendo ser utilizado em elementos onde se busca uma redução de armadura de tração e aumento da vida útil, contribuindo para a segurança e qualidade.DOI: http://dx.doi.org/10.4995/HAC2018.2018.5369
Determinación de las curvas de Wöhler en fatiga a flexotracción de un hormigón de muy alta resistencia sometido a temperatura elevada
Authors: Rios Jimenez Jose David , Cifuentes Bulté Héctor , Medina Encina Fernando 
Published: March 2018

El uso de hormigones de muy alta resistencia en depósitos de almacenamiento de energía es una de las aplicaciones en las que se está estudiando la idoneidad de su uso frente a otros tipos de materiales. Las principales ventajas que aporta está opción son la de ser un material resistente, con capacidad para almacenamiento de energía térmica y todo ello para un material accesible y de bajo coste en comparación con otras alternativas. En el proceso de almacenamiento se pueden alcanzar temperaturas que rondan los 300 ºC durante periodos prolongados de tiempo. El estudio de la durabilidad de estas estructuras en periodos con exposición de cargas variables y temperatura, así como los posibles daños ocasionados en la matriz de hormigón, son de gran importancia debido a las consecuencias que pueden propiciar. En este trabajo nos hemos centrado en el estudio del comportamiento frente a fallo por fatiga a flexotracción de un hormigón de muy alta resistencia diseñado por nosotros. Para ello se han realizado dos amasadas idénticas de hormigones reforzados con fibras de acero. Todos los hormigones con la idéntica matriz y una relación de fibras de un 2.5% en volumen. Los hormigones fueron reforzados con dos tipos de fibras diferentes: una de ellas el modelo RC-80/35-BN, de 35 mm de longitud y extremos en forma de gancho, y otra el OL-13/0.16, de 13 mm de longitud y extremos lisos, ambas de Bekaert. La primera amasada fue ensayada a temperatura ambiente y la segunda, fue calentada hasta 300 ºC. La temperatura de cada amasada estuvo durante un período de al menos 24 horas, de manera que se asegurase que cualquier punto de la matriz alcanzase dicha temperatura. Se realizaron ensayos a fatiga de flexión en tres puntos sobre probetas prismáticas de 440x100x100 mm condicionadas por un defecto local inicial reproducido mediante una entalla, de 1/6 del canto, en la zona central de la probeta. A partir de los resultados experimentales se obtuvieron las curvas de Wöhler de cada uno de los hormigones y se realizó un análisis de las mismas relacionándolo con las propiedades mecánicas de los hormigones y una comparativa del efecto de la temperatura en la vida útil del material.DOI: http://dx.doi.org/10.4995/HAC2018.2018.5527
Modelización del mecanismo de pérdida de consistencia provocado por arcillas en pastas de cemento con superplastificantes base policarboxilato
Authors: Borralleras Pere , Segura I. , Aguado A. 
Published: March 2018

Las arcillas son un elemento que interfiere negativamente en la producción y calidad del hormigón. La presencia de arcillas en las arenas implica sobrecostes de producción del hormigón y mermas en la durabilidad. Pero en el caso de tratarse previamente las arenas para eliminar su contenido en arcillas, se genera un impacto ambiental notable, relacionado con elevados consumos de agua, generación de residuos sólidos e incremento del consumo de recursos naturales.Los aditivos superplastificantes basados en PCE son los tipos con mayor sensibilidad a las arcillas. La ponencia pretende explicar los mecanismos de interferencia causado por las arcillas sobre los aditivos de PCE, justificada a partir de la estructura del polímero y de la tipología de cada arcilla.Adicionalmente, se presentará el impacto que causa cada parte de la estructura del polímero de PCE en la sensibilidad ante arcillas y cual es la aportación observada cuando se modifican dichas partes estructurales de la molécula.Finalmente, se presentará la aportación potencial de las vías de mejora identificadas, tanto desde su punto de vista económico como ambiental.DOI: http://dx.doi.org/10.4995/HAC2018.2018.5634
Roads & SDGs, tradeoffs and synergies: learning from Brazil’s Amazon in distinguishing frontiers
Authors: Pfaff Alexander , Robalino Juan , Reis Eustaquio J. , Walker Robert , Perz Stephen , Laurance William , Bohrer Claudio , Aldrich Steven , Arima Eugenio , Caldas Marcellus , Kirby Kathryn R. 
Published: March 2018

AbstractTo reduce SDG tradeoffs in infrastructure provision, and to inform searches for SDG synergies, the authors show that roads’ impacts on Brazilian Amazon forests varied significantly across frontiers. Impacts varied predictably with prior development – prior roads and prior deforestation – and, further, in a pattern that suggests a potential synergy for roads between forests and urban growth. For multiple periods of roads investments, the authors estimate forest impacts for high, medium and low prior roads and deforestation. For each setting, census-tract observations are numerous. Results confirm predictions for this kind of frontier of a pattern not consistent with endogeneity, i.e., short-run forest impacts of new roads are: small for relatively high prior development; larger for medium prior development; and small for low prior development (for the latter setting, impacts in such isolated areas could rise over time, depending on interactions with conservation policies). These Amazonian results suggest ‘SDG strategic’ locations for infrastructure, an idea the authors note for other frontiers while highlighting major differences across frontiers and their SDG opportunities.
Astronomical tunings of the Oligocene–Miocene transition from Pacific Ocean Site U1334 and implications for the carbon cycle
Authors: Beddow Helen M. , Liebrand Diederik , Wilson Douglas S. , Hilgen Frits J. , Sluijs Appy , Wade Bridget S. , Lourens Lucas J. 
Published: March 2018

Abstract. Astronomical tuning of sediment sequences requires both unambiguous cycle pattern recognition in climate proxy records and astronomical solutions, as well as independent information about the phase relationship between these two. Here we present two different astronomically tuned age models for the Oligocene–Miocene transition (OMT) from Integrated Ocean Drilling Program Site U1334 (equatorial Pacific Ocean) to assess the effect tuning has on astronomically calibrated ages and the geologic timescale. These alternative age models (roughly from  ∼ 22 to  ∼ 24 Ma) are based on different tunings between proxy records and eccentricity: the first age model is based on an aligning CaCO3 weight (wt%) to Earth's orbital eccentricity, and the second age model is based on a direct age calibration of benthic foraminiferal stable carbon isotope ratios (δ13C) to eccentricity. To independently test which tuned age model and associated tuning assumptions are in best agreement with independent ages based on tectonic plate-pair spreading rates, we assign the tuned ages to magnetostratigraphic reversals identified in deep-marine magnetic anomaly profiles. Subsequently, we compute tectonic plate-pair spreading rates based on the tuned ages. The resultant alternative spreading-rate histories indicate that the CaCO3 tuned age model is most consistent with a conservative assumption of constant, or linearly changing, spreading rates. The CaCO3 tuned age model thus provides robust ages and durations for polarity chrons C6Bn.1n–C7n.1r, which are not based on astronomical tuning in the latest iteration of the geologic timescale. Furthermore, it provides independent evidence that the relatively large (several 10 000 years) time lags documented in the benthic foraminiferal isotope records relative to orbital eccentricity constitute a real feature of the Oligocene–Miocene climate system and carbon cycle. The age constraints from Site U1334 thus indicate that the delayed responses of the Oligocene–Miocene climate–cryosphere system and (marine) carbon cycle resulted from highly non-linear feedbacks to astronomical forcing.
Irreversible ocean thermal expansion under carbon dioxide removal
Authors: Ehlert Dana , Zickfeld Kirsten 
Published: March 2018

Abstract. In the Paris Agreement in 2015 countries agreed on holding global mean surface air warming to well below 2 °C above pre-industrial levels, but the emission reduction pledges under that agreement are not ambitious enough to meet this target. Therefore, the question arises of whether restoring global warming to this target after exceeding it by artificially removing CO2 from the atmosphere is possible. One important aspect is the reversibility of ocean heat uptake and associated sea level rise, which have very long (centennial to millennial) response timescales. In this study the response of sea level rise due to thermal expansion to a 1 % yearly increase of atmospheric CO2 up to a quadrupling of the pre-industrial concentration followed by a 1 % yearly decline back to the pre-industrial CO2 concentration is examined using the University of Victoria Earth System Climate Model (UVic ESCM). We find that global mean thermosteric sea level (GMTSL) continues to rise for several decades after atmospheric CO2 starts to decline and does not return to pre-industrial levels for over 1000 years after atmospheric CO2 is restored to the pre-industrial concentration. This finding is independent of the strength of vertical sub-grid-scale ocean mixing implemented in the model. Furthermore, GMTSL rises faster than it declines in response to a symmetric rise and decline in atmospheric CO2 concentration partly because the deep ocean continues to warm for centuries after atmospheric CO2 returns to the pre-industrial concentration. Both GMTSL rise and decline rates increase with increasing vertical ocean mixing. Exceptions from this behaviour arise if the overturning circulations in the North Atlantic and Southern Ocean intensify beyond pre-industrial levels in model versions with lower vertical mixing, which leads to rapid cooling of the deep ocean.
Topographical change caused by moderate and small floods in a gravel bed ephemeral river – a depth-averaged morphodynamic simulation approach
Authors: Lotsari Eliisa S. , Calle Mikel , Benito Gerardo , Kukko Antero , Kaartinen Harri , Hyyppä Juha , Hyyppä Hannu , Alho Petteri 
Published: March 2018

Abstract. In ephemeral rivers, channel morphology represents a snapshot at the end of a succession of geomorphic changes caused by floods. In most cases, the channel shape and bedform migration during different phases of a flood hydrograph cannot be identified from field evidence. This paper analyses the timing of riverbed erosion and deposition of a gravel bed ephemeral river channel (Rambla de la Viuda, Spain) during consecutive and moderate- (March 2013) and low-magnitude (May 2013) discharge events, by applying a morphodynamic model (Delft3D) calibrated with pre- and post-event surveys by RTK-GPS points and mobile laser scanning. The study reach is mainly depositional and all bedload sediment supplied from adjacent upstream areas is trapped in the study segment forming gravel lobes. Therefore, estimates of total bedload sediment mass balance can be obtained from pre- and post-field survey for each flood event. The spatially varying grain size data and transport equations were the most important factors for model calibration, in addition to flow discharge. The channel acted as a braided channel during the lower flows of the two discharge events, but when bars were submerged in the high discharges of May 2013, the high fluid forces followed a meandering river planform. The model results showed that erosion and deposition were in total greater during the long-lasting receding phase than during the rising phase of the flood hydrographs. In the case of the moderate-magnitude discharge event, deposition and erosion peaks were predicted to occur at the beginning of the hydrograph, whereas deposition dominated throughout the event. Conversely, the low-magnitude discharge event only experienced the peak of channel changes after the discharge peak. Thus, both type of discharge events highlight the importance of receding phase for this type of gravel bed ephemeral river channel.
Female EFL Learners' Needs of an Advanced Communication Course in an Arab University
Authors: Nagour Mona , Shukri Nadia 
Published: March 2018

This needs analysis is conducted to examine the EFL communication skills needs of female EFL undergraduate students at a female Arab university located in Jeddah, Saudi Arabia from their own perspectives. The significance of this study is to help the administrators and educators at this university to identify and accommodate the students’ current needs and lacks which are required for the advanced course, i.e. English 102 (ENGL 102). The participants were 52 female undergraduate students from diverse majors enrolled in English 101 (ENGL 101) course. A questionnaire adapted from (Gravatt, Richards, & Lewis, 1997) was used to examine what the students believe they need and lack in an EFL communication skills. The questionnaire findings showed that some of the needs of EFL learners match with their weaknesses in listening and speaking skills. The results have also showed that in spite of the main focus of ENGL 102, which is to enhance the listening and speaking skills, students have expressed that they need more writing and reading skills practice implementations besides listening and speaking. This illustrates that the four-language skills reading, writing, speaking and listening are central and need to be integrated in the teachers’ pedagogies Nevertheless, when comparing the result of the questionnaire and the objectives of ENGL 102, it has been found that there is no discrepancy between them. Finally, the students prefer more practice, activities and vocabulary learning to improve their listening and speaking skills.
Aesthetic Relational Knowledge of the Field: A Revised Concept of Awareness in Gestalt Therapy and Contemporary Psychiatry
Authors: Lobb Margherita Spagnuolo 
Published: March 2018

AbstractThis article supports the need for psychotherapy and psychiatry to overcome the fragmentation of scientific knowledge. The author focuses briefly on the evolving relationship between psychotherapy and society, providing a brief overview of today's clinical needs. She then proposes a new development in the clinical concept of awareness from the optics of the field: aesthetic relational knowledge as a clinical tool that emerges from the phenomenological, aesthetic, relational, and process-oriented approach that is the Gestalt method. Therapeutic competence, in other words, is empathic and resonates with the client in a cocreated field. A clinical example will demonstrate how the concept of aesthetic relational knowledge can be used in a Gestalt therapy setting.
Being Smart Is Not Enough to Ensure Success: Integrating Personal Development into a General Education Course
Authors: Whitehall Anna Petra , Hill Laura G. , Yost Denise M. , Kidwell Kimberlee K. 
Published: March 2018

AbstractLife skills, including conflict management, flexibility in response to change, and effective communication, are critical to success in college and career. Most university administrators and employers believe that students should learn foundational life skills in college, but for the most part universities do not explicitly teach these skills as part of the general undergraduate education experience. The goal of the present study was to examine whether personal development can be effectively fostered in a general education course. It reports on a theory-based course designed to increase leadership, adaptive coping skills, and mental well-being. It also demonstrates through a quasi-experiment that participation in this course is related to social and psychological outcomes such as increased adaptability to change and social integration. These skills will support students in being successful in college and beyond.
Psychometric Properties of the Inventory of Student Experiences in Undergraduate Research
Authors: Cater Melissa , Ferstel Sarah D. , O'Neil Carol E. 
Published: March 2018

Abstract
Student participation in undergraduate research (ugr) may be influenced by interest in research, future career and educational plans, perceived value of undergraduate research experiences, or perceived competence in research skills. The purpose of this study was to develop a questionnaire that could be used to validly and reliably assess students' perceived value of undergraduate research and perceived confidence in their research skills. Undergraduate student participants ranged in age from seventeen to fifty-two years. Respondents were predominantly female, white, and nonparticipants in ugr. Thirteen items were generated. The internal structure of the instrument was established by extracting two latent constructs using exploratory factor analysis. The cumulative percentage of variance explained by the constructs was approximately 55 percent. Results from the confirmatory factor analysis corroborated the internal structure of the instrument. The most parsimonious model was a twelve-item, two-factor solution with adequate fit. Reliability estimates were generally above 0.80. Initial assessment of the psychometric properties of the Inventory of Student Experiences in Undergraduate Research suggests that it may be a viable tool for undergraduate research programs to use in assessing the results of efforts to increase the value of ugr as well as student confidence in their own research skills.
“The Spirit of the Builder”: The Library Career of Julia Carson Stockett
Authors: Lindell Lisa R. 
Published: March 2018

ABSTRACT
The personal history of Julia Carson Stockett contributes to and interweaves with the larger story of American women professional librarians in the early twentieth century. Stockett's experiences illuminate the achievements made by professional women in support and encouragement of one another. Throughout her career, Stockett sustained a commitment to her professional status and responsibilities and her vision of librarianship. The diversity of libraries and populations she served, notably in the West and Midwest, mark her work as exceptional. At the heart of her vocational choices were her facility for organization and her desire to bring books and reading to those lacking access. An examination of her correspondence, her published articles, contemporary newspaper accounts, and other sources expands the historical scholarship on the central and diverse roles of early professional women librarians as they carried forward the work of developing libraries and shaping a profession.