28 research outputs found
Advances in measuring parameters of the air-void system in hardened concrete
No full textTo improve the freezing and thawing resistance of concrete, air bubbles are entrained and distributed evenly and closely. Evaluation of the parameters of the air-void system in hardened concrete is detailed in ASTM C457 “Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete.” Microscopical methods are used to determine traverse lengths of air voids, aggregates, and pastes on the polished surface of concrete samples. Since this manual measurement is time-consuming, tedious, and dependent on skills of operators, automated methods are preferred. This study recommends improvements to both the ASTM C457 test protocol and the metrics that are used to characterize the air void system.
A flatbed scanner is used to acquire a single high resolution image of the polished surface of a concrete sample. The concrete surface is polished and treated with phenolphthalein and orange powder to facilitate segmentation of air bubbles, paste and aggregate phases. The image is processed using ImageJ, Photoshop, and Matlab software. A three-phase image is generated with air, paste, and aggregate phases shown in white, gray, and black, respectively. Using the three-phase image, ASTM C457 parameters can be readily determined by computer.
To validate the new approach, six groups of concrete samples were examined in a “blind study.” The concrete samples were donated by CTLGroup which had previously evaluated the air void system using the standard ASTM C457 test method. A good agreement between the two methods was shown except in the case of samples with lightweight aggregates.
The mechanism of freezing and thawing damage is complicated and theories proposed by researchers cannot explain all the observations or establish a clear relationship between the spacing of air void, the freezing rate and the paste properties. In many respects, these theories complement each other. Air entrainment is effective and reliable to resist freezing and thawing for concrete designed for outside exposure in the cold climate. The structure of the air-void system is critical for the frost resistance of concrete and the spacing factor is one of the most significant parameters of the air-void system.
A new approach to spacing factor is developed in this study using two-dimensional images to provide better information than linear traverse or point count methods. The average distance of pastes to the nearest air void, the percentage of protected pastes, the area fraction of air voids, and the surface area of air voids are two-dimensional parameters which can be used to evaluate the freezing and thawing performance considering the physical properties and the mechanism of freezing of concrete. A comparative study is conducted between the two-dimensional parameters and the one-dimensional parameters in ASTM C457 and the advantages of the two-dimensional parameters are presented.Item withdrawn by Laura Spradlin ([email protected]) on 2014-04-29T17:55:35Z
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Modern Landscape Representation of Hakka Culture
No full textHakka culture is a combination of ancient Chinese culture, aboriginal southern culture and hilly environment, whose influence spreads more than 80 countries and regions in the world. It is more difficult to summarize the regional landscape representation techniques of Hakka culture under the background of modern landscape. The author makes a comparative study of landscape representation techniques of the three typical Hakka landscapes, putting forward modern landscape ideas of Hakka culture in order to provide reference for construction of other regional landscapes
Modern Landscape Representation of Hakka Culture
No full textHakka culture is a combination of ancient Chinese culture, aboriginal southern culture and hilly environment, whose influence spreads more than 80 countries and regions in the world. It is more difficult to summarize the regional landscape representation techniques of Hakka culture under the background of modern landscape. The author makes a comparative study of landscape representation techniques of the three typical Hakka landscapes, putting forward modern landscape ideas of Hakka culture in order to provide reference for construction of other regional landscapes
A systematic review of technology-enhanced L2 listening development since 2000
No full textSince 2000, technology-enhanced L2 listening development (TELD) has been increasingly investigated. However, systematic reviews concerning the technologies, learning tasks, and outcomes of TELD remain limited. To fill this gap, we conducted a systematic review of publications from 2000 to 2022 on TELD from the perspectives of technologies, learning tasks, and learning outcomes. Forty-six articles from Web of Science were screened by predefined criteria and analysed based on a step-by-step procedure using the PRISMA framework. The findings revealed 13 types of technology and 19 learning tasks useful for TELD. TELD was effective both in terms of building listening skills and enhancing learner emotions. The studies showed that TELD supported learner interactions, encouraged active engagement, and augmented various learning tasks. Based on the findings, we developed a TELD model consisting of two parts: “Within cognitive systems,” in which learners deal with cognitive schemata, listening strategy application, and listening practice via solid attention; “outside of cognitive systems,” in which TELD can construct and reconstruct cognitive schemata, support listening practices, encourage and guide listening strategy application, and improve learner emotions and attention by providing learning materials and activities based on listening-related knowledge, listening exercises with feedback, prompts and feedback on listening strategy application, and a sense of enjoyment and comfort
Zoom supported emergency remote teaching and learning in teacher education: A case study from Hong Kong
No full textThe shift from face-to-face teaching to emergency remote teaching has become the new normal due to the pandemic in 2020. However, little research has been conducted in Hong Kong to investigate pre-service teachers’ perceptions of the immediate adoption and delivery of online face-to-face teaching. In response to this call, the present research conducted a questionnaire survey with 48 pre-service teachers at a Hong Kong university to examine their perceptions of Zoom as a viable alternative to the suspended traditional face-to-face delivery mode of instruction. It also discussed key factors that lead to better online learning outcomes. The results showed that the participants had overall positive perceptions of Zoom-supported synchronous online education. The Zoom feature that most students considered useful was screen sharing on computers. Zoom-supported synchronous online learning benefited students by helping them to attend class meetings remotely, study course materials and content, communicate and collaborate with their instructors and classmates, and develop a sense of community and social presence. Four main factors may influence learners’ perceptions of synchronous online learning: the quality of online communication and collaboration, learning efficiency, learner autonomy and the usability of technology
Effects of digital game elements on engagement and vocabulary development
No full textDigital game-based vocabulary learning (DGBVL) integrates key game elements such as Challenges, Rewards, Human-Computer Interactions (HCI), Multimedia, and Fantasy. Although the overall effectiveness of digital games in enhancing English-as-a-foreign-language (EFL) vocabulary knowledge development is well-established, the specific roles of individual game elements remain underexplored. To fill the gap, we developed a DGBVL program incorporating the five elements to examine their impact on learner engagement and vocabulary acquisition among 50 Chinese university students. Data collection methods included an eye-tracker, pre-post-delayed tests, and semi-structured interviews. The results indicated that Challenges significantly engaged learners, while deep engagement in HCI and limited engagement in Fantasy positively influenced vocabulary knowledge development. Our findings refine existing theories on DGBVL by elucidating how game elements individually and collaboratively facilitate learner engagement and vocabulary knowledge development across the phases of Preactional/Forethought, Actional/Performance, and Post-actional/Self-reflection learning
Super-Resolution of Low-Quality Images Based on Compressed Sensing and Sequence Information
No full textA bio-inspired and switchable H<sup>+</sup>/OH<sup>−</sup> ion-channel for room temperature exhaled CO<sub>2</sub> chemiresistive sensing
No full textInspired by the CO2-induced reversible activation mechanism of the slow anion channel 1 (SLAC1) in plant stomatal guard cells during plant photosynthesis, we designed and prepared a CO2- switchable H+/OH− ion channel (CSPH ion channel). A high-performance chemiresistive room temperature CO2 sensor has been prepared based on this CSPH ion channel. The obtained CO2 room temperature sensor γ-CD-MOF@RhB exhibits high sensitivity (Rg/R0 = 1.50, 100 ppm), excellent selectivity, good stability (less than 5% reduction in 30 days response value), and 99.96% consistency with commercial infrared CO2 meter. The practical limit of detection (pLOD) of the γ-CD-MOF@RhB sensor reaches 10 ppm at room temperature toward CO2, which is the lowest for reported MOF-derived chemiresistive room temperature CO2 sensors so far. Ion conduction mechanism studies have shown that the CSPH ion channel behaves as a CO2-switchable H+/OH− ion channel with a switching point of approximately 60 000 ppm CO2. As an application attempt, the fabricated low pLOD CO2 sensor has been used for human exhaled CO2 detection to compare CO2 concentration in the breath of individuals before and after exercise and COVID-19. It was also logically indicated that the average concentration of human exhaled CO2 after COVID-19 recovery is different for undiseased subjects.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Bio-Electronic
Language-based colorization of scene sketches
No full textBeing natural, touchless, and fun-embracing, language-based inputs have been demonstrated effective for various tasks from image generation to literacy education for children. This paper for the first time presents a language-based system for interactive colorization of scene sketches, based on semantic comprehension. The proposed system is built upon deep neural networks trained on a large-scale repository of scene sketches and cartoonstyle color images with text descriptions. Given a scene sketch, our system allows users, via language-based instructions, to interactively localize and colorize specific foreground object instances to meet various colorization requirements in a progressive way. We demonstrate the effectiveness of our approach via comprehensive experimental results including alternative studies, comparison with the state-of-the-art methods, and generalization user studies. Given the unique characteristics of language-based inputs, we envision a combination of our interface with a traditional scribble-based interface for a practical multimodal colorization system, benefiting various applications.</p
Construction and Application of Diversified Knowledge Model for Paper Reviewers Recommendation
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