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Cementing wells in salt rock is a challenging operation, particularly due to changes in cement properties as a result of interaction with dissolved rock, which can lead to poor cementing quality and risks associated with leakage. In this paper, the effects of NaCl content on the properties of the cement in contact with selected salt rock samples are investigated. The results are suitable for determining the dependencies of cement properties required for the selection of a plugging system formulation suitable for the geological and technical target conditions in well construction. The cement samples were exposed to aqueous NaCl solutions for 28 days after which no significant changes in mechanical properties, such as compressive strength, gas permeability coefficient, expansion/shrinkage and contact strength with the salt rock, were observed. Based on the results, the optimum strength properties of the cement were determined at a saturation coefficient (Kn) between 0.6 and 0.8 where up to 21% increase in the compressive strength was identified possibly due to the formation of strong bondings between the cement and the salt rock. In addition, the growth of salt crystals inside the cement at high concentrations of NaCl was determined through increasing linear dimensions of the cement sample by 2.5% that leads to the formation of microcracks and channels as confirmed by the obtained results of gas permeability tests, namely an increase from 0.38 to 0.91 mD. [ABSTRACT FROM AUTHOR]

Abstract Roof stability is a critical concern in coal mines, as the potential for roof collapse poses a significant risk to miners' safety and productivity. Roof stability is heavily influenced by the time-dependent properties of the rock mass above the workings. This study uses rock displacement testing to examine the effect of time-dependent properties on roof stability and resistance reduction in coal mines in Iran. The study employed laboratory-based rock displacement tests on samples collected from coal mines in Iran, subjected to varying stress levels over time, to simulate the gradual deterioration of rock mass strength in underground mining conditions. The samples were monitored for displacement under these conditions to quantify the reduction in roof resistance over time and assess its effect on roof stability. The study found that areas with high stress at equilibrium gradually fail with time, and the stress transfers from the failure zone into deeper solid rock. The results demonstrate that varying viscous parameters can lead to different relaxation behaviors and stress distribution. Furthermore, incorporating strength degradation into numerical simulation can capture the failure under creep conditions and improve the accuracy of predicting time-dependent roof failure. This research aims to enhance safety measures and reduce the risk of collapses by investigating the time-dependent properties of roof stability through rock displacement testing in Iran's coal mines. The study's innovative approach uses numerical simulation based on the viscoelastic-plastic model to simulate the time-dependent behavior of the rock and incorporate strength degradation into the simulation. The results provide valuable insights into the time-dependent behavior of rock mass in coal mines in Iran and contribute to developing strategies for improving roof stability and lessening the chance of roof collapses. The instantaneous elastic strain was 4.35 × 10–4, and creep simulation was activated to run for a time equivalent to 2 × 106 s.

Copyright of Journal of Prevention & Treatment For Stomatological Diseases is the property of Journal of Prevention & Treatment For Stomatological Diseases Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study describes the development process and examines the construct validity of an English placement test of oral communication (EPT OC) developed at a Midwestern university in the United States. This test includes a one‐on‐one oral interview and paired discussion task, and test performance is judged on an analytic rating scale. A confirmatory factor analysis conducted on the ratings of 338 students who took the initial fully operational EPT OC revealed the test structure was represented by a correlated four‐factor model with interactional competence, fluency, pronunciation/comprehensibility, and grammar/vocabulary as sub‐constructs, in line with its targeted theoretical framework. Both tasks were effective in measuring the targeted sub‐constructs, but the sub‐constructs were not sufficiently distinct from each other to completely justify a four‐factor model. The findings provide some support for the proposed interpretations of the EPT OC test scores but indicate the need for some modifications to the assessment, such as more thorough rater training and/or revised rating scales to better distinguish the targeted sub‐constructs. [ABSTRACT FROM AUTHOR]

This study scrutinized the effects of words' superiority, regularity, frequency and length on the intermediate and advanced EFL learner's visual word recognition. Moreover, it attempted to check whether each of these parameters could be statistically a significant predictor on recognition tasks. Accordingly, 118 intermediate and 127 advanced adult EFL learners were selected randomly from English Language Institutes based on their performance on the McMillan Placement Test (MPT). The needed data was collected through a developed Visual Word Recognition Test (WORT) and the Peabody Picture Vocabulary Test (PPVT). The findings indicated that all the mentioned factors significantly affected both the intermediate and the advanced EFL learners' overall word recognition by varying degrees (words' frequency, length, superiority and regularity, respectively), however, the advanced learners' recognition was generally faster on both recognition tests. Moreover, words' regularity was found to play a more effective role for the intermediates than the advanced learners on recognition tasks. Furthermore, words' frequency, regularity and length were found to be proper predictors on comprehension tasks. [ABSTRACT FROM AUTHOR]

Copyright of Systems Engineering & Electronics is the property of Journal of Systems Engineering & Electronics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aims: This study investigated the views of children and young people with Down syndrome of their schools, with the aim of increasing the understanding of the features of successful educational placements and the implications for planning, consultation and support. Methods: The study used a participatory visual interview approach, aiming to reduce language and memory demands and task avoidance due to intimidation. Findings: The findings indicate that the research techniques used did help the participating young people to highlight experiences and issues that were of importance to them. Their reports about what was good and what was difficult about school are original and enlightening and provide important insights about their experiences and preferences. Limitations: This was a small, convenience sample and the reporting of interview findings represents the perspective of the participating young people with Down syndrome. Two school tours were limited by restrictions imposed by school staff. School tours and interviews were not repeated. However, the interviews did provide new and unique information about children and young people with Down syndrome's experiences of school. The study was part of wider research mapping the educational experiences of a large group of children and young people with Down syndrome, identifying predictors, strategies and approaches that contribute to successful placements. Only three young people with Down syndrome were interviewed and this small number affects the generalisability of results. Conclusions: The study identifies what is valued by the participating young people with Down syndrome, and provides guiding principles and practical implications. It presented an opportunity for children and young people with Down syndrome to communicate their views, and for those views to influence their school experience. Ethical considerations emphasise those relating to the involvement of children and young people with Down syndrome who have additional developmental and communication vulnerabilities. The dissemination supports advocacy at a systemic, school and individual level. [ABSTRACT FROM AUTHOR]

Abstract A much-debated question in the L2 assessment field is if computer familiarity should be considered a potential source of construct-irrelevant variance in computer-based writing (CBW) tests. This study aims to make a partial validity argument for an online source-based writing test (OSWT) designed for English placement testing (EPT), focusing on the explanation inference. Score interpretations on the OWST are proposed and supporting evidence is sought in terms of test-takers’ self-confidence in and preferences for CBW tests (two interrelated aspects of computer familiarity) and L2 writing ability. Ninety-seven ESL students demonstrating two different levels (higher and lower levels) of L2 writing ability studying at a US university completed the OSWT and an online questionnaire asking about their attitudes towards CBW tests. A series of statistical and thematic analyses revealed that most of the test-takers held self-confidence in and preferences for CBW tests for reasons related to previous CBW experience (e.g., familiarity with CBW, useful tools/functions available on computers) regardless of L2 writing ability. The higher-level test-takers obtained significantly higher scores on the OSWT than their lower-level counterparts. Test-takers’ preferences were a significant predictor of the OSWT scores only in the higher-level group. The findings largely support the validity of proposed score interpretations on the OSWT. Implications are discussed in terms of test fairness and the construct of CBW tests.

Copyright of Djoussour El-maarefa is the property of Association of Arab Universities and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The common practice of standardizing foot placement in postural research and in clinical practice may serve to increase postural sway. The focus of this study was to investigate foot placement strategies in the tandem (anteroposterior, AP) and side-to-side (mediolateral, ML) stance in healthy adults. Foot placement was either experimenter-controlled or selected by the participant. Greater sway was observed for the AP stance than the ML stance, where sway was minimal. When foot placement was self-selected, participants recruited additional degrees of freedom by rotating both feet outward to expand the base of support; they narrowed their stance width in the AP stance only. Self-selection served to decrease AP sway for the AP stance and increase ML sway for both the AP and ML stances. A dynamical measure, the largest Lyapunov exponent, supported the finding that self-selection of foot placement serves to stabilize posture. The implication is that improvements in postural control were due primarily to self-selection of foot placement and not to adjustments in stance width. Experimental and perhaps clinical procedures should be revised to allow participants to self-select foot placement during postural tasks. [ABSTRACT FROM AUTHOR]

Porosity is an important part of cement paste microstructure, which significantly influences the mechanical properties (especially durability and strength) of cement-based materials. Electrochemical impedance spectroscopy (EIS) is a non-destructive method used to measure the pore system utilizing a range of frequencies of electric current, which is fed to the cement paste by stainless steel electrodes. The pore volume is obtained from the pore resistance and the matrix capacitance measured by EIS. This paper deals with the evaluation of porosity based on resistance values from EIS on a sample of pure CEM I 42.5R Portland cement paste at 3 different hydration times (age 7, 14, 28 days). [ABSTRACT FROM AUTHOR]

A much-debated question in the L2 assessment field is if computer familiarity should be considered a potential source of construct-irrelevant variance in computer-based writing (CBW) tests. This study aims to make a partial validity argument for an online source-based writing test (OSWT) designed for English placement testing (EPT), focusing on the explanation inference. Score interpretations on the OWST are proposed and supporting evidence is sought in terms of test-takers' self-confidence in and preferences for CBW tests (two interrelated aspects of computer familiarity) and L2 writing ability. Ninety-seven ESL students demonstrating two different levels (higher and lower levels) of L2 writing ability studying at a US university completed the OSWT and an online questionnaire asking about their attitudes towards CBW tests. A series of statistical and thematic analyses revealed that most of the test-takers held self-confidence in and preferences for CBW tests for reasons related to previous CBW experience (e.g., familiarity with CBW, useful tools/functions available on computers) regardless of L2 writing ability. The higher-level test-takers obtained significantly higher scores on the OSWT than their lower-level counterparts. Test-takers' preferences were a significant predictor of the OSWT scores only in the higher-level group. The findings largely support the validity of proposed score interpretations on the OSWT. Implications are discussed in terms of test fairness and the construct of CBW tests. [ABSTRACT FROM AUTHOR]

The use of low-grade calcined clays is the only potential material available in large quantities to meet the requirements of eco-efficient supplementary cementitious materials by decreasing the clinker content in blended types of cement or cement content in concrete. In the present paper, six mortar mixtures with a constant w/b ratio were used to investigate the mechanical and durability properties of mixtures substituted with low-grade calcined clays with/without limestone compared to PC and silica fume mixtures. The results show that using calcined clays with low or intermediate purity (i.e., kaolinite content) leads to enhanced durability besides the comparable strength development characteristics compared to PC mortar. In this regard, the addition of 30% calcined clay with/without limestone led to a marked decrease (about 80 and 40%) in chloride ion diffusion coefficient (Da) and an increase in surface chloride content (Cs) compared to the reference mixture. In addition, the utilization of calcined clay with a kaolinite content of 56.7% led to a reduction of 52% in Da and an increase of 140% in electrical resistivity compared to silica fume binder. The primary reason for the better performance is attributed to the refined pore structure and dense microstructure of the cement paste with the calcined clay pozzolan compared to PC and silica fume. [ABSTRACT FROM AUTHOR]

The English General Scholastic Ability Test (GSAT), a nationwide high-stakes college entrance exam in Taiwan, has commonly served as a placement test for streaming college freshmen into EFL classes. There has, however, been scant research reported on the feasibility of using an admission test for EFL placement. This study aims to investigate the accuracy and validity of placement decisions being made using the English GSAT scores, with a focus on its relations with the General English Proficiency Test (GEPT) and students' subsequent performance in class. Quantitative data, including the English GSAT scores, the GEPT High-Intermediate Listening and Reading scores, and the English final course grades, were collected and statistically analyzed from four EFL classes with a total of 100 students at a university in Taiwan. The English GSAT was found to function well to place students into distinctively lower or higher level of EFL classes but did not discriminate well for the borderline cohort. A three-level placement using the English GSAT appeared to be a better differentiation between each proficiency cluster. High achievers in the English GSAT appeared to perform better on the GEPT listening and reading tests than did low achievers. Yet, apart from the GEPT reading test, the English GSAT yielded weak predictive power of student course attainment, which seemingly varied across classes, hinging on course designs and grading policies. Implications drawn from the results of the investigation were further discussed. [ABSTRACT FROM AUTHOR]

This study details the development of a local test designed to place university Spanish students (n = 719) into one of the four different course levels and to distinguish between traditional L2 learners and early bilinguals on the basis of their linguistic knowledge, regardless of the variety of Spanish they were exposed to. Early bilinguals include two groups—heritage learners (HLs), who were exposed to Spanish in their homes and communities growing up, and early L2 learners with extensive Spanish exposure, often through dual immersion education, who are increasingly enrolling in university Spanish courses and tend to pattern with HLs. Expert instructor judgment and learner corpora contributed to item development, and 12 of 15 written multiple-choice test items targeting early-acquired vocabulary had differential item functioning (DIF) according to the Mantel–Haenszel procedure, favoring HLs. Recursive partitioning revealed that vocabulary score correctly identified 597/603 (99%) of L2 learners as such, and the six HLs whose vocabulary scores incorrectly identified them as L2 learners were in the lowest placement groups. Vocabulary scores also correctly identified 100% of the early L2 learners in the sample (n = 7) as having a heritage profile. Implications for the local context and for placement testing in general are provided. [ABSTRACT FROM AUTHOR]

The aim of the study is to investigate the impact of placement test, pop-quizzes and portfolio assessment on class attendance and language achievement. The study also encompasses gender and faculty as other independent variables that affect the students' class attendance and language achievement. The data gathered from a total of 307 students studying English in the elective preparatory class of a state university in Turkey are analysed through SPSS 25. In the study, descriptive and inferential statistics are implemented. Descriptive analyses such as frequency and percentage are applied in order to reveal information about participants. Independent Sample t-tests, one-way ANOVA, post hoc tests and regression analyses are also performed to determine the relationship between dependent and independent variables. The findings in the study show that portfolio tasks are the most important factors for students' class attendance and language achievement, which demonstrates that authentic assessment is an important factor. It is found that males do not attend the classes more than females but females are more successful than males. In addition, the faculty as another independent variable does not have a significant effect on class attendance but engineering faculty has a significant impact on language achievement rather than economics faculty. [ABSTRACT FROM AUTHOR]

The present paper deals with the hardness of cement mortars prepared with recycled materials that are potential supplementary cementitious materials (SCM). Two potential SCMs (aerated concrete powder (ACP) and concrete powder) were investigated and compared with a reference (neat cement) sample and a sample containing metakaolin (MK). The long-term performance of the mortars was studied up to the age of one year. Based on the compressive strength tests at different ages, neither concrete powder nor ACP significantly decreases the compressive strength at a 10% substitution ratio. The samples were studied with two types of static hardness tests: the Brinell hardness test and the depth sensing indentation test at two different load levels. The hardness test results indicated that the standard deviation of the results is lower at a higher load level. In the case of metakaolin and concrete powder, the change in the compressive strength was observable in the hardness test results. However, in case of the ACP, the compressive strength decreased, while the hardness increased, which can be traced back to the filler effect of aerated concrete powder. Finally, using the DSI test, the hardness results were analyzed on an energy basis. The analysis highlighted that the change in the hardness is connected to the elastic indentation energy, while it is independent from the dissipated (plastic) indentation energy. [ABSTRACT FROM AUTHOR]

The aim of this study is to examine the effects of cement stabilization on the mechanical stress of compressed stabilized earth blocks (CSEBs) and adobe stabilized earth bricks (ASEBs). Hence, this work is based on an experimental study carried out in order to determine the geotechnical properties of the samples soil, namely, the dry particle size analysis after washing, the particle size distribution by sedimentometry, Atterberg limits, and the preparation of specimens with different levels of cement proportions. Moreover, single compression and three-point bending compression out on specimens measuring 4x4x4cm3 and 4x4x16cm3 respectively. The findings indicate that dosing with 8% cement results in a clear increase in compression stress of approximately 25.55% for CSEBs compared to the reference set at 0% and 22.85% for ASEBs. On the other hand, for a dosage of 4%, we observe a slight increase in stress by simple compression of around 3.26% for CSEBs and 3.14% for ASEBs. For three-point bending compression for a cement dosage of 8%, there is also an increase in stress of about 25% for the CSEBs compared to the reference taken at 0% and 23.02% for the ASEBs. [ABSTRACT FROM AUTHOR]

This paper summarizes experimental studies using Nuclear Magnetic Resonance (NMR) to evaluate cement porosity, pore size distribution, and other characteristics such as Calcium Silicate Hydrate (CSH) gel structure and morphology. The first known paper on NMR experiments to investigate cement pastes was published in 1978. Two main NMR parameters, the so-called longitudinal T1 and transverse T2 relaxation times, are commonly measured and analyzed, representing the water response which is trapped in the cement. The hydration process reported in this paper was found to be monitored from as low as 10 min to longer than 365 days. Other studies conducted experiments by using NMR, especially during the 1980s. These studies employed variations in methodologies and frequencies, making data comparison difficult. Additionally, different spectrometers and NMR concepts, as well as operating characteristics, were used. Therefore, it is challenging to reconcile results from previous NMR studies on cement. Other significant hurdles are different cement types, water/cement ratio, and curing conditions. One notable observation is that there has not been any comprehensive laboratory work related to NMR on oilfield cement types, including porosity and hydration. Two recent studies have presented NMR measurements on class G and class H cements. [ABSTRACT FROM AUTHOR]

The present study aimed at investigating the relationship between literary translation and argumentative writing. The initial sample consisted of 60 advanced translation students. After administrating O:if

When the COVID-19 pandemic made it impossible to do in-person, on campus testing, we were forced to create a new system to screen International Teaching Assistants (ITA) for Temple university. We used this opportunity to address many of the concerns and problems that we had identified with the previous test, and created a new test that could be administered virtually. The new test (the TU ITA Test) makes it possible to test potential ITAs at any time, allowing departments to make instructor placement decisions far in advance. The TU ITA Test also seems to better assess ITAs' interactional competence than the previous test, suggesting it might be a more valid ITA screening measure. [ABSTRACT FROM AUTHOR]

Copyright of International Architecture is the property of Omniscient Pte. Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Accurate placement within levels of an ESL program is crucial for optimal teaching and learning. Commercially available tests are commonly used for placement, but their effectiveness has been found to vary. This study uses data from the Ohio Program of Intensive English (OPIE) at Ohio University to examine the value of two commercially available tests (the TOEFL ITP and the Michigan EPT) and a locally developed writing test for accurate placement decisions. Placement accuracy was measured in terms of the relationship between test scores and (1) appropriate placement levels for individual students according to their teachers, and (2) student performance in the classes. Findings support the continued use of multiple measures for more accurate placement decisions in the study context. However, the relationship between test scores and student performance, measured by students' grades in the actual course levels and their success in advancing to a higher course level as additional indicators of the extent to which placement tests provide an accurate indication, was weak when analyzed through multiple regression and cross-tabulation, suggesting that factors other than initial proficiency are primarily determinative of student success when students have been accurately placed. [ABSTRACT FROM AUTHOR]

Since 2012 an interdisciplinary and culturally heterogeneous team composed of more than 30 people has been engaged in the complex process of conceiving, designing and validating an online placement test with formative orientation called SELF (Système d'Evaluation en Langues à visée Formative), developed and already deployed in six different languages – Italian and English as pilots, followed by French, Mandarin, Japanese and Spanish. Its results are used to form groups and classes of similar ability, or to identify students' strengths and weaknesses in three macro skills (listening, reading, limited writing). In this report, we describe the steps the multilingual team is currently taking to transform SELF into a diagnostic test that will fulfill its original formative purpose and provide students and other stakeholders with more precise information about their performance. This can be done in two ways, by using the data automatically recorded by the online administration platform more thoroughly and by enriching user feedback with clear and informative graphics. This will enhance the validity of our test, and help close the gap between testing and learning. [ABSTRACT FROM AUTHOR]

• The University of Utah uses a process-oriented, locally-developed and scored writing test. • Utah's Writing Placement Exam is well-aligned with writing course learning outcomes. • The writing construct of the WPE supports some revision. • The WPE has advantages over standardized assessments in its flexible, individualized approach. This review of the University of Utah's Writing Placement exam evaluates the possibilities of the exam's construct, addresses the tool's limitations, and analyzes it in light of similar placement tools. The review concludes that although there are challenges specifically related to the scalability, security, and language ideology of the exam, its holistic nature, local assessors, and process-oriented view of writing ensure its effectiveness as a writing placement test. [ABSTRACT FROM AUTHOR]

The interaction among different sizes of cracks in materials is one of the key factors leading to the damage of brittle materials. Based on the Kachanov method, the expressions for the stress intensity factors of two collinear cracks with unequal length were obtained and the interaction effect was analyzed. A compression test of a cement mortar specimen containing two cracks and numerical analysis using RFPA2D were performed. The results indicate that the crack interaction can almost be neglected when the crack distance reaches the length of the large crack; the two respective collinear cracks in the specimen grow and do not affect each other when the crack distance reaches the large crack length. The results of compression test and numerical analysis are both in agreement with the theoretical result. [ABSTRACT FROM AUTHOR]

Abstract Novel polyphosphate superplasticizers were synthesized by copolymerization reaction between 2-(methacryloyl oxy) ethyl phosphate monomer and the macromonomer polyethylene glycol methacrylate ester at different molar ratios. The synthesized phosphated comb polymers were characterized by size exclusion chromatography and elemental analysis and their dispersing performance in cement was assessed via mini slump tests in cement paste. The phosphated comb polymers exhibited superior dispersing performance over conventional polycarboxylate comb polymers (PCEs), were less retarding on cement and showed comparable robustness against sulfate and clay impurities. These properties can be explained by the high calcium complexing capacity of the phosphate groups. Thus, phosphated comb polymers present a viable alternative to polycarboxylate superplasticizers. [ABSTRACT FROM AUTHOR]

Cement-based materials typically have a relatively high compressive strength and a relatively low tensile strength. In this paper, multiscale silicon carbide whiskers (SW) were used to improve mechanical properties of oil-well cement stone. The structure and properties of whisker cement stone were analyzed via mechanical testing and cement sheath integrity. The results demonstrated that multiscale SW mixing showed a positive hybrid effect and could effectively improve the compressive strength, the flexural strength, and the splitting tensile strength of oil-well cement stone by 8.96%, 137.44% and 27.96%. The modulus and porosity of the whisker cement stone significantly reduced. The filling effect, whisker pinning, the pullout, and the whisker bridging were regarded as effective mechanisms for the addition of SW when improving the mechanical properties and microstructures of oil-well cement stone. [ABSTRACT FROM AUTHOR]

Marble has been commonly used as a building material since ancient times. The disposal of waste materials from the marble industry, consisting of sludge that is composed of powder mixed with water, is one of the current worldwide environmental problems. This experimental study aims to valorize marble powder, which is achieved by grinding the sludge as filler added to the cementitious matrix of self-compacting concrete (SCC). The main purpose of this work is to evaluate the marble filler effects on the rheology in the fresh state and on the hardened properties of SCCs compared to those of limestone filler. To this end, two SCCs, SCCM and SCCL, manufactured using marble powder and limestone filler, respectively, were prepared and tested. The fresh properties of the two SCCs' mixtures were determined by slump flow, L-box, V-funnel, sieve stability, bulk density, and air content. Tests on hardened SCCs included compressive strength, homogeneity, and quality in terms of ultrasonic pulse velocity and durability against carbonation and water penetration. In addition, scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to analyze the specimens. [ABSTRACT FROM AUTHOR]

In this article, we focus on cement-binded Ba0.85Sr0.15Zr0.1Ti0.9O3 ceramics for pyroelectric applications. It was prepared with the Ba0.85Sr0.15Zr0.1Ti0.9O3-to-cement ratios of 85%:15% and 80%:20% by weight. In order to improve the effectiveness of thermal-to-electric energy conversion, the synchronized switch harvesting on inductor technique is experimentally tested on cement composites. Our experimental findings reveal that this concept based on synchronized switch harvesting on inductor can significantly increase the amount of power extracted from pyroelectric materials. Furthermore, the optimized power across 15% and 20% cement composites were found to be 7.2 and 6 nW, respectively, in series synchronized switch harvesting on inductor and 8.5 and 7 nW, respectively, in parallel synchronized switch harvesting on inductor. These values are significantly higher when compared with non-switched circuit for pyroelectric applications. Although, from the obtained results for the prepared composites, the power output is less when compared with pure Ba0.85Sr0.15Zr0.1Ti0.9O3, they have some advantages: these composites can be made without any sintering process and are compatible for structural applications. [ABSTRACT FROM AUTHOR]

Abstract The present contribution investigates the use of air quotes in English academic presentations held by and addressed to scholars of various disciplines and from different cultural and language backgrounds. The first part of the paper provides a detailed formal description of the air quotes identified based on gesture realization and gesture-speech coordination. A close analysis of the former confirms the existence of a conventional gesture format to which alternative realizations approximate, while the analysis of gesture-speech coordination highlights strong regularities in terms of type of air quotes' recognizable referent and gesture placement with respect to such referent. In the second part of the paper a functional analysis is presented, in which it is argued that air quotes have two key pragmatic functions: a) they "manage the match" between linguistic representations and propositional content by signaling the relative vagueness/preciseness of the terms used, and b) they "manage attributions" by indexing the speaker's commitment to the truth of the proposition, and hence maintain her/his epistemic authority and credibility as a scholar. The analysis provides insights into how air quotes relate metapragmatically to a specific discourse genre situated in an international and multidisciplinary academic discourse community. Highlights • Air quotes have a standard realization that includes a specific gesture space • Air quotes tend to be performed on top of the lexicalizations of their referents • Air quotes tend to co-occur with metapragmatic comments • Air quotes have predication functions • Air quotes may signal the vagueness/preciseness of a lexical representation • Air quotes may index the speaker's commitment to a propositional content [ABSTRACT FROM AUTHOR]

Abstract In this paper, an innovative method was proposed to synthesize an alite-ye'elimite clinker by adopting a secondary heat treatment step in a different sintering atmosphere after a traditional Portland cement (PC) clinker has been heated up at 1450 °C. It was found that a pure gaseous SO 2 or mixed gas containing the gaseous SO 2 used facilitated the decomposition of C 3 S and the consumption of C 3 A in the PC clinker. Simultaneously, anhydrite (CaSO 4), ye'elimite (3CaO·3Al 2 O 3 ·CaSO 4 , C 4 A 3 $) and ternesite (4CaO·2SiO 2 ·CaSO 4 , C 5 S 2 $) coexisted in the alite-ye'elimite clinker, resulting from gas-solid reactions during sintering. The experimental results also showed that the compressive strength of the synthesized alite-ye'elimite cement was higher than that of PC. Moreover, its setting times were shorter than that of PC. [ABSTRACT FROM AUTHOR]

In the present study, compressive strength results of geopolymers produced by ordinary Portland cement (OPC) as aluminosilicate source have been modeled by artificial neural networks. Six main factors including NaOH concentration, water glass to NaOH weight ratio, alkali activator to cement weight ratio, oven curing temperature, oven curing time and water curing regime each at 4 levels were considered for designing. A total of 32 experiments were conducted according to the L32 array proposed by the method. The neural network models were constructed by 10 input parameters including NaOH concentration, water glass to NaOH weight ratio, alkali activator to cement weight ratio, oven curing temperature, oven curing time, water curing regime, water glass content, NaOH content, Portland cement content and test trial number. The value for the output layer was the compressive strength. According to the input parameters in feed-forward back-propagation algorithm, the constructed networks were trained, validated and tested. The results indicate that artificial neural networks model is a powerful tool for predicting the compressive strength of the geopolymers in the considered range. [ABSTRACT FROM AUTHOR]

Abstract An analytical model for predicting the relative chloride diffusion coefficient in cementitious materials at different degrees of water saturation is presented in this paper. The model is developed based on the Nernst-Einstein equation and conductivity of cementitious electrolyte, as well as on moisture distribution in the pore structure. Good agreement is found between the model and the experimental data. With the help of the model, the chloride diffusion coefficient of cementitious material at unsaturated state can be determined according to the chloride diffusion coefficient at saturated state, the degree of water saturation and the average pore diameter of the material. A detailed discussion about the inputs and outputs of the model is given in order to facilitate its application for engineering practice. [ABSTRACT FROM AUTHOR]

Abstract Clinkers with alite-belite-ye'elimite (ABY) are considered as eco-friendly cements. Clinkering (2 Kg) of two types of ABY clinkers was optimized: standard-ABY, with CaF 2 and ZnO as dopants (32.6 wt% alite, 30.4 wt% β-C 2 S and 15.6 wt% ye'elimite) and αABY, with CaF 2 , ZnO, B 2 O 3 , Na 2 O (14.4 wt% alite, 37.1 wt% β-C 2 S, 18.5 wt% α′ H -C 2 S and 7.5 wt% ye'elimite). Zn and F were mainly incorporated in alite and ferrite as dopants determined by EDS semi-quantitative analysis. The effect of dopants on the hydration of the cement mortars has been tested. Thus, standard-ABY develops 29.9 MPa compressive strengths at 1 day while αABY does 16.8 MPa, mainly due to the higher amount of alite of the former. The presence of α′ H -C 2 S in αABY increases mechanical strengths at 28 days of hydration from 44.7 MPa of standard-ABY to 74.9 MPa. [ABSTRACT FROM AUTHOR]

Abstract In this study, the C-A-S-H composition, morphology and density are characterized for Limestone Calcined Clay Cement (LC3-50) blends containing clays with various kaolinite contents. Significant incorporation of aluminium is observed for LC3-50 blends compared with reference Portland cement (PC), and this incorporation increases with the kaolinite content of the calcined clay. No change of C-A-S-H morphology was observed by Transmission Electron Microscopy (TEM) between reference PC and LC3-50 blends, with a "fibrillar" morphology for all samples. The determination of the density of C-A-S-H measured by 1H NMR also shows very similar results with a bulk density close to 2.0 g·cm−3 and a solid density of around 2.8 g·cm−3 for all systems. [ABSTRACT FROM AUTHOR]

Abstract Concrete as the most common building material of our time is responsible for about 6% of total anthropogenic CO 2 emission. Reduction of Portland cement clinker and replacement with ground limestone was identified as an efficient solution to reduce the environmental impacts of concrete. Preliminary studies showed that drying shrinkage of concretes made of limestone-rich cements is significantly affected by the content and the chemical-mineralogical characteristics of ground limestone. Meanwhile, it was concluded that available prediction models are unable to predict the drying shrinkage of concrete with high limestone contents precisely, especially for limestones with different chemical-mineralogical properties. In this paper, an analytical model is proposed based on the mechanics of porous materials and thermodynamic laws to predict the drying shrinkage of concrete made with cements containing limestone up to 70 wt.‐%. Specifically, this model considers the influence of content and chemical-mineralogical properties of limestone on the drying shrinkage. [ABSTRACT FROM AUTHOR]

Abstract As a first step toward characterising structural build-up of high-strength, printable concrete mixes, the structural build-up of cement pastes of varying compositions and rheological properties is investigated. It is demonstrated that applying low shear rates over short measurement periods does not always result in the achievement of flow-onset in stiffer cementitious materials, commonly used in digital construction. For such materials, a characteristic delay exists before the effective shear rate reaches the applied shear rate. This leads to effective strains in the materials tested and consequently to the erroneous characterisation of structural build-up. A strain-based approach is suggested here as a more appropriate method for characterising structural build-up in the case of stiff materials. Maintaining a low, constant shear rate among various measurements is not necessary if the total effective strain is kept constant. Investigations on pastes with different compositions show that pastes in which a portion of the cement was replaced with micro-silica and fly ash exhibited high structuration rate. The use of secondary cementitious materials (SCM) appears to be similarly appropriate measure to make cementitious materials 'printable' when compared to using set-accelerators, in the absence of inline mixing of accelerators in the printhead. Highlights With regard to the structural build-up of cementitious materials: • The approach of stress growth tests with a constant shear rate applied for a fixed duration is critically analysed. • A strain-based approach is suggested as an appropriate method in case of materials for digital construction. • Maintaining a low, constant shear rate among measurements is not necessary if the total effective strain is kept constant. • Partial replacement of cement with secondary cementitious materials results in a high structuration rate. • Effective strain is about 1.5 units in all cases where static yield stress can be measured, i.e., flow onset is reached. [ABSTRACT FROM AUTHOR]

Abstract The purpose of this paper is to develop a model for predicting water vapour sorption hysteresis of cement-based materials. The sorption hysteresis was modelled based on the pore size distribution (PSD) and the pore network. The PSD of gel and capillary pores was predicted from the adsorption isotherm. The results indicated that the distribution had two peaks at 3.8 nm and 11 nm of the pore diameters, referring to gel and small capillary pores, respectively. The predicted ratio of gel water to evaporable interlayer water was not a constant, but decreased with an increasing hydration degree. When RH was below 0.25, the predicted sorption hysteresis was solely influenced by the hysteresis of water in interlayer spaces and minor hydrates. The hysteresis in gel pores, small and large capillary pores influenced the shape of desorption isotherms within the RH ranges of 0.25–0.85, 0.35–0.98 and 0.4–1, respectively. Highlights • Pore size distribution of concrete was predicted from adsorption isotherms. • The water in gel pores and interlayer spaces within the C-S-H gel was decoupled. • The ratio of gel water to evaporable interlayer water decreased with hydration. • Contributions of different types of water to hysteresis were analysed. • Gel and capillary pores influenced the hysteresis in different RH ranges. [ABSTRACT FROM AUTHOR]

Abstract Experimental evidence of a new acid degradation mechanism in alkali-activated cements (AACs) micro-doped with copper (Cu) and cobalt (Co) is presented in this work. Cu and Co incorporation into binary metakaolin and basic oxygen furnace (BOF) slag-based AACs reduced bulk permeable porosity and acid penetration and retarded the formation of calcium sulfate phases upon exposure to acid. Analysis of microstructural evolution and elemental mobility using X-ray diffraction and electron microprobe analysis (EMPA) showed that Cu and Co doping was associated with major differences in AAC leaching patterns when exposed to sulfuric acid. Converging lines of evidence suggest that acid resistance is improved by the preferential mobilization of Cu and Co, along with other multivalent cations (i.e., magnesium), at the acid degradation front(s), stabilizing the AAC binder and inhibiting further deterioration. [ABSTRACT FROM AUTHOR]

Abstract: The effect of hydroxyapatite (HA) addition on the in vitro bioactivity of calcium aluminate cement (CA) was studied. Nano-particles of pure single-phase calcium aluminate were prepared via solid state reaction at high temperature. An ultra-pure nano-sized hydroxyapatite prepared by the sol-gel method was used to formulate a composite of 1:1 CA:HA. In vitro bioactivity of CA and its composite was evaluated by soaking in stimulated body fluid (SBF). Physico-mechanical properties, pH and concentration of calcium and phosphorous ions were estimated. The structure of samples was investigated using X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) coupled with energy dispersive spectroscopy (EDS). Antimicrobial activity of both materials formulated was studied. The results showed that the composite CA/HA has better mechanical and bio-compatibility properties when compared to the pure material. The antimicrobial activity showed that, both CA and CA/HA have a moderate antimicrobial effect on all the microorganisms tested; the inhibition zone range was 13.0-16.0 mm. [ABSTRACT FROM AUTHOR]

Abstract: For this work calcium aluminate cement (CAC) was prepared with Al2O3 content ≥ 70 mass-% and a nanographene oxide solution (GOS) additive. SEM, XRD, calorimetry, and electrical conductivity (EC) measurements were carried out. Studies have shown that the addition of GOS has an effect on the hydration of CAC compared to the cement paste only with water. It was determined that nanographene oxide affected the formation of crystal hydrates: in a cement stone with a nanographene oxide additive, the intensities of CAH10 hydrates were shown to be higher. It was determined that nanographene oxide affects CAC at a temperature of 20 °C as follows: the heat flow maximum in a cement paste with the nanographene oxide suspension is fixed after 18.5 h, i.e., 2.5 h earlier than cement paste mixed with water. Electrical conductivity examination showed that the addition of GOS in the CAC suspension accelerated ion release. [ABSTRACT FROM AUTHOR]

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Highlights • A method is proposed for improvement of distribution network resilience. • Using Monte Carlo simulation and fragility curves, failure samples are generated. • A forward dynamic programming algorithm is used to obtain the path of repair teams. • The objective function considers the importance of loads and the cost of outages. • The numerical results proved that the proposed model is accurate and efficient. Abstract Predictive planning for restoration and emergency reaction before occurrence of hurricane is an effective action in reducing time and cost of electricity interruption and improving resilience in overhead distribution networks. Traditionally, approaches in load and system recovery are constructed based on reliability studies, with the consideration of equipment failure. However, widespread outages due to the extreme natural events with low probability and high destruction intensity have different properties in comparing the interruptions due to the failures in equipment. Therefore, this paper proposes a new method for restoration and emergency reaction planning. The purpose of this method is resilience improvement of distribution network against hurricane. In the proposed pre-hurricane repair team placement model (PHRTPM), using Monte Carlo simulation method and fragility curves, different failure samples of poles and conductors of medium voltage distribution network are generated according to the predicted speed of hurricane. Furthermore, the forward dynamic programming algorithm is used to determine the path of the repair teams. In this method, using a square grid topology, the optimum locations of utility teams are achieved. The objective function of problem considers the importance of loads and the cost of outages. In the numerical studies, the proposed model is implemented on a modified and real distribution network in Iran which consisted of 81 buses. The results are discussed and the sensitivity analysis is performed for various parameters. [ABSTRACT FROM AUTHOR]