Debonding failure of RC beams retrofitted with Near Surface Mounted FRP Reinforcement

Near Surface Mounted (NSM) Fibre Reinforced Polymer (FRP) reinforcement is an effective rehabilitation solution to strengthen RC structures, as it can enable higher load carrying capacity and ductility than conventional Externally Bonded Reinforcement (EBR). However, the performance of elements strengthened in flexure is still controlled by bond failure between the NSMR system and the concrete substrate. This can reduce both the effectiveness and safety of NSMR systems and should be accounted for in design. The development of high stresses due to the abrupt termination of NSMR is the main cause for the dominant end debonding failure. This type of failure is not well understood and needs to be examined in detail. The aim of this work is to achieve a comprehensive understanding of bond behaviour and debonding mechanisms of the NSMR in flexural strengthening applications both experimentally and theoretically so as to enable the development of practical and reliable design methods for RC beams strengthened in flexure with NSMR. An analytical elastic model is developed to facilitate a fundamental understanding of the distribution of bond stresses along the NSMR, especially in the region around the termination point. The model identifies differences of stress states between EBR and NSMR. However, since it is based on elastic analysis and continuum mechanics, it is unable to represent bond behaviour of NSMR at high load levels. This issue can only be examined in detail via specially developed experimental work. A total of ten RC beams, including two control beams and eight beams strengthened in flexure with CFRP and BFRP bars or strips, are tested to examine the overall structural behaviour of RC beams retrofitted with NSMR of different embedment lengths. Tested beams are heavily instrumented to examine the influence of yield penetration along the internal steel bars on the bond behaviour of the NSM reinforcement within the shear spans and the resulting debonding mechanisms. NSMR enhanced flexural capacity by up to 50% and the dominant failure mode was end debonding after yielding. The experimental results show that yielding of the steel reinforcement penetrates in the shear span much further than predicted through classic section analysis, reaching near or even beyond the termination point. The experimental evidence is used to develop a new simple, yet effective methodology to estimate the minimum embedment length. The new design method is validated against an extensive database collected from literature and is found to provide more accurate and reliable results

Policy Uncertainty and Firm Cash Holdings

This research examines the relation between government economic policy uncertainty and firm cash holdings. We find evidence that policy uncertainty is positively related to firm cash holdings due to firms’ precautionary motives and, to a lesser extent, investment delays. The relation between policy uncertainty and cash holdings is more pronounced for firms dependent on government spending and extends beyond business cyclicality. Further analysis indicates that the effects of policy uncertainty on corporate cash holdings are distinct from those of political, market, or other macroeconomic uncertainty

A Turn-On Fluorescence-Based Fibre Optic Sensor for the Detection of Mercury

The design, development, and evaluation of an optical fibre sensor for the detection of Hg2+ in aqueous media are discussed in detail in this paper. A novel fluorescent polymeric material for Hg2+ detection, based on a coumarin derivative (acting as the fluorophore) and an azathia crown ether moiety (acting as the mercury ion receptor), has been synthesized. The fluorophore was covalently immobilized onto the fibre surface by polymerisation using the ion imprinting technique and exhibited a significant increase in fluorescence intensity in response to Hg2+ via a photoinduced electron transfer (PET) mechanism. The sensor provided a response over a concentration range of 0–28 µM with an acceptable response rate of around 11 min and a recovery rate of around 30 min in a Tris-EDTA buffer solution. A detection limit of 0.15 µM was obtained with a possibility of improvement by changing the thickness of the polymer layer and using a more sensitive detector. High-quality performance is seen through a high selectivity for Hg2+ over other metal ions, excellent photo-stability and reversibility which was also demonstrated, making this type of sensor potentially well suited for in-situ monitoring of mercury in the environment

A Method for Knowledge Representation to Design Intelligent Problems Solver in Mathematics Based on Rela-Ops Model

Knowledge-base is a fundamental platform in the architecture of an intelligent system. Relations and operators are popular knowledge in practice knowledge domains. In this paper, we propose a method to represent the model by combining these kinds of knowledge, called the Rela-Ops model. This model includes foundation components consisting of concepts, relations, operators, and inference rules. It is built based on ontology and object-oriented approaches. Besides the structure, each concept of the Rela-Ops model is a class of objects which also have behaviors to solve problems on their own. The processing of algorithms for solving problems on the Rela-Ops model combines the knowledge of relations and operators in the reasoning. Furthermore, we also propose a knowledge model for multiple knowledge domains, in which each sub-domain has the form as the Rela-Ops model. These representation methods have been applied to build knowledge bases of Intelligent Problems Solver (IPS) in mathematics. The knowledge base of 2D-Analytical Geometry in a high-school is built by using the Rela-Ops model, and the knowledge base of Linear Algebra in university is designed by using the model for multiple knowledge domains. The IPS system can automatically solve basic and advanced exercises in respective courses. The reasoning of their solutions is done in a step-by-step approach. It is similar to the solving method by humans. The solutions are also pedagogical and suitable for the learner’s level and easy to be used by students studying 2D-Analytical Geometry in high-school and Linear Algebra in university.This work was supported in part by the Universiti Teknologi Malaysia (UTM) under Research University Grant Vot-20H04, in part by the Malaysia Research University Network (MRUN) Vot 4L876 and in part by the Fundamental Research Grant Scheme (FRGS) Vot 5F073 through the Ministry of Education Malaysia

Encouraging Dialogue around Social Issues with Latinx Students Through Literature Discussion and Culturally Relevant Literature

This teacher research study examines literature discussions with fourth and fifth grade Latinx students about books that reflect Latinx experiences. For this study, the following questions are explored (1) What social issues do students discuss in literature groups? (2) How do literary response strategies influence student dialogue? And (3) How does my theoretical frame influence my decision making as a teacher? Theories that informed the construction of the literature discussions and the decision making occurring throughout the study are examined closely. The theories intertwine and bridge education and students’ experiences as a resource in learning more about the educational setting. In this study, the discussions of students and the literature response strategies are explored as the data is analyzed to examine the student discussions around issues of immigration, family separation, borders, and so much more. The findings in this study indicate that the experiences of Latinx students are integral to the educational setting and an education that invites who they are enhances their learning experiences. Latinx students are eager for learning opportunities that invite their voices and stories. It is through the construction and assessment of the educational setting that educators can promote culturally responsive, relevant, and sustaining teaching experiences that go beyond the classroom setting. Latinx students build relationships with each other and their teachers as they engage in discussions that allow them to share and learn with each other. This study is a reminder of the crucial role teachers play in creating such powerful spaces and the value that Latinx students bring into the classroom when invited to discuss, engage, and create powerful learning experiences

Intensified Antituberculosis Therapy in Adults with Tuberculous Meningitis

BACKGROUND Tuberculous meningitis is often lethal. Early antituberculosis treatment and adjunctive treatment with glucocorticoids improve survival, but nearly one third of patients with the condition still die. We hypothesized that intensified antituberculosis treatment would enhance the killing of intracerebral Mycobacterium tuberculosis organisms and decrease the rate of death among patients. METHODS We performed a randomized, double-blind, placebo-controlled trial involving human immunodeficiency virus (HIV)-infected adults and HIV-uninfected adults with a clinical diagnosis of tuberculous meningitis who were admitted to one of two Vietnamese hospitals. We compared a standard, 9-month antituberculosis regimen (which included 10 mg of rifampin per kilogram of body weight per day) with an intensified regimen that included higher-dose rifampin (15 mg per kilogram per day) and levofloxacin (20 mg per kilogram per day) for the first 8 weeks of treatment. The primary outcome was death by 9 months after randomization. RESULTS A total of 817 patients (349 of whom were HIV-infected) were enrolled; 409 were randomly assigned to receive the standard regimen, and 408 were assigned to receive intensified treatment. During the 9 months of follow-up, 113 patients in the intensified-treatment group and 114 patients in the standard-treatment group died (hazard ratio, 0.94; 95% confidence interval, 0.73 to 1.22; P=0.66). There was no evidence of a significant differential effect of intensified treatment in the overall population or in any of the subgroups, with the possible exception of patients infected with isoniazid-resistant M. tuberculosis. There were also no significant differences in secondary outcomes between the treatment groups. The overall number of adverse events leading to treatment interruption did not differ significantly between the treatment groups (64 events in the standard-treatment group and 95 events in the intensified-treatment group, P=0.08). CONCLUSIONS Intensified antituberculosis treatment was not associated with a higher rate of survival among patients with tuberculous meningitis than standard treatment. (Funded by the Wellcome Trust and the Li Ka Shing Foundation; Current Controlled Trials number, ISRCTN61649292.)

Preparation and Foliar Application of Oligochitosan - Nanosilica on the Enhancement of Soybean Seed Yield

Oligochitosan with weight average molecu-lar weight (Mw) of 5000 g/mol was prepared by gamma Co-60 radiation degradation of 4% chitosan solution containing 0.5% H2O2 at 21 kGy. Nanosilica with size of 10 – 30 nm was synthesized by calcination of acid treated rice husk at 700o C for 2 h. The mixture of 2% oligo-chitosan-2% nanosilica was prepared by dispersion of nanosilica in oligochitosan solution. Oligochitosan, nanosilica and their mixture were characterized by gel permeation chromatography (GPC), transmission electr-on microscopy (TEM), X-ray diffraction (XRD), energy dispersive x-ray spectroscopy (EDX), Ultraviolet-visible spectroscopy (UV-Vis), and Furrier transform infrared spectroscopy (FT-IR). Effect of foliar application of oli-gochitosan and oligochitosan-nanosilica on soybean seed yield was conducted in experimental field. Results indi-cated that soybean seed yield increased 10.5 and 17.0% for oligochitosan and oligochitosan-nanosilica, respect-tively for the control. Radiation degraded oligo-chitosan and its mixture with nanosilica can be potentially used for cultivation of soybean with enhanced seed yield