Axial Load and Bending Moment Behaviour of Square High Strength Concrete (HSC) Columns Reinforced with Steel Equal Angle (SEA) Sections

This paper presents the behaviour of square high-strength concrete (HSC) specimens reinforced longitudinally with steel equal angle (SEA) sections under different loading conditions. For the same cross-sectional area, a SEA section has a higher second moment of area than a steel bar, which results in a greater bending stiffness of the concrete member reinforced with SEA sections. Also, the area of confined concrete is greater in concrete members reinforced with SEA sections compared to members reinforced with steel bars, which results in higher strength and ductility. A total of 8 specimens of 210 mm square cross-section and 800 mm height were constructed and tested. The specimens were divided into two groups with four specimens in each group. Group R-S50 specimens serve as the reference group and were reinforced longitudinally with four N12 (12 mm diameter) deformed steel bars. Group A30-S50 specimens were reinforced longitudinally with four A30 (29.1 mm x 29.1 mm x 2.25 mm) SEA sections. All specimens were reinforced laterally with R10 (10 mm diameter) plain steel bars and spaced at 50 mm centres. The main variables considered in the study included the type of longitudinal reinforcement and the magnitude of load eccentricity. It was obtained from the experimental results that specimens reinforced longitudinally with SEA sections showed greater ductility compared to specimens reinforced longitudinally with steel bars under different loading conditions

Behavior of High-Strength Concrete Columns Reinforced with Galvanized Steel Equal-Angle Sections under Different Loading Conditions

Experimental results are presented for a new method of reinforcing concrete columns with galvanized steel equal-angle (GSEA) sections. For the same cross-sectional area, a GSEA section has a higher second moment of area than a conventional steel bar, which leads to a higher bending stiffness of the GSEA reinforced concrete member. In addition, the area of confined concrete is higher in GSEA reinforced concrete members than in steel bar reinforced members, which results in higher strength and ductility. The experimental program involved testing of 20 square, high-strength concrete (HSC) specimens under concentric axial load, eccentric axial load, and four-point loading. The specimens were reinforced longitudinally with either four N12 (12-mm-diameter deformed steel) bars or four GSEA sections and transversely with R10 (10-mm-diameter plain steel) bars. The specimens were 800 mm high with a 210 x 210 mm square cross section. Fifteen specimens were tested under either a concentric or eccentric axial load. The remaining five specimens were tested under four-point loading. Effects of the type of longitudinal reinforcement, spacing of transverse reinforcement, and loading conditions on the behavior of HSC specimens were investigated and discussed. Experimental results showed that, in general, specimens reinforced with GSEA sections had higher load-carrying capacities than the specimens reinforced with steel bars. In addition, the postpeak load-deformation behavior was observed to be more pronounced in specimens reinforced with GSEA sections than in specimens reinforced with steel bars

Introducing particle interphase model for describing the electrical behaviour of nanodielectrics

This study proposes a new model for describing the electrical behaviour of nanocomposites. Unlike other models in the literature, this model has concentrated on the role of an interphase layer within the boundaries of nanoparticles. The experimental part investigates this role by filling an epoxy matrix with two types of surface-modified silicon nitride nanofiller: (a) the particles were dried at 200 °C, and (b) the particles were calcinated at 1050 °C. Electrical characterization showed that the epoxy which was filled with the calcinated particles has considerably better dielectric performance. Given that thermal and dielectric spectroscopy results demonstrate that the matrix molecular dynamics and polar content are comparable for all the investigated samples, the variations in the dielectric performance point to the particle interphase as an essential reason. As shown by infrared spectroscopy, the complex surface chemistry of the dried particles suggests a particle interphase with a high concentration of localized electronic states, which may enhance charge transport through hopping/tunnelling conduction. On the other hand, calcinating the particles results in a particle interphase with wider band gap, which may work as an energy barrier for charge movement. Consequently, this study highlights the paramount importance of particle interphase for designing dielectric properties of nanodielectrics.</p

Who uses the internet as a source of nutrition and dietary information? An Australian population perspective

Background: The Internet contains a plethora of nutrition information. Health organizations are increasingly using the Internet to deliver population-wide health information and interventions. Effective interventions identify their target population and their needs; however, little is known about use of the Internet as a source of nutrition information. Objective: The aim was to assess the change in prevalence and demographic characteristics of Western Australian adults accessing the Internet as a source of nutrition information and identify specific information needs. Methods: Data were pooled from the Western Australian Department of Health’s 3-yearly Nutrition Monitoring Survey Series telephone survey between 1995 and 2012 of 7044 participants aged 18 to 64 years. Outcome variables were the main sources of nutrition information used in the last year and yes/no responses to 4 suggestions to what would make it easier to eat a healthy diet. Sociodemographic variables were collected. Results: The proportion of respondents using the Internet for nutrition information increased from <1% in 1995-2001 to 9.1% in 2004 and 33.7% in 2012. Compared to 2004, logistic regression showed that the odds of using the Internet for this information increased significantly in 2009 (OR 2.84, 95% CI 2.07-3.88) and 2012 (OR 5.20, 95% CI 3.86-7.02, P<.001). Respondents using the Internet as a source were more likely to be female (OR 1.30, 95% CI 1.05-1.60, P=.02), live in a metropolitan area (OR 1.26, 95% CI 1.03-1.54, P=.03), born in countries other than Australia/UK/Ireland (OR 1.41, 95% CI 1.07-1.85, P=.02), more educated (university: OR 2.46, 95% CI 1.77-3.42, P<.001), and were less likely to be older (55-64 years: OR 0.38, 95% CI 0.25-0.57, P<.001). The majority of respondents agreed the following information would assist them to make healthier choices: more ways to prepare healthy foods (72.0%, 95% CI 70.7-73.3), quicker ways to prepare healthy foods (79.0%, 95% CI 77.8-80.1), how to choose healthy foods (68.8%, 95% CI 67.5-70.1), and knowing more about cooking (54.7%, 95% CI 53.3-56.1). Those using the Internet for nutrition information were more likely than nonusers to want to know quicker ways to prepare healthy foods (83.0% vs 78.1%, P=.005) and information on choosing healthy foods (76.3% vs 67.3%, P<.001)

Enhanced dielectric properties of polyethylene/hexagonal boron nitride nanocomposites

A range of nanocomposites based on a polyethylene polymer and hexagonal boron nitride (hBN) filler has been explored in this study. The dielectric properties of the nanocomposites, which consisted of 2 wt %, 5 wt %, 10 wt %, 20 wt %, and 30 wt % of hBN, have been compared to the dielectric properties of the unfilled polyethylene blend. Scanning electron microscopy (SEM) revealed that the hBN was uniformly distributed in the polyethylene matrix, although large amounts of agglomerates were present in the nanocomposites containing more than 10 wt % of hBN. The incorporation of hBN into polyethylene resulted in a highly disordered morphology in comparison to the unfilled polyethylene, in which this effect was more pronounced with increasing hBN content. This is consistent with the increasing crystallisation temperature as the hBN content increases, as shown by differential scanning calorimetry (DSC), where the hBN acted as a highly effective nucleating due to the strong interactions between the polyethylene and the hBN. This strong interaction is again reflected in the thermal decomposition temperature which similarly increases with increasing hBN content. The study demonstrates the remarkable electrical properties of the prepared nanocomposites, where the breakdown strength monotonically increased as a function of hBN content, even with a very high 30 wt % of hBN. The improvement in electrical properties, even at high hBN concentrations, is contradictory to the reported results in the literature and are mainly attributed to the hydrophobic surface of the hBN particles

Effect of Resin/Hardener Stoichiometry on Electrical Behavior of Epoxy Networks

By changing the ratio of resin to hardener, a series of epoxy resin samples has been produced with differing network structures and different retained chemical functionalities. The resulting materials were characterized by thermal analysis, dielectric spectroscopy, DC conductivity, and DC and AC breakdown strength measurements, to explore the effect of network structure and chemical composition on molecular dynamics and electrical properties. Differential scanning calorimetry showed that the glass transition temperature is primarily determined by the crosslinking density and indicates that, under the range of conditions employed here, side reactions, such as etherification or homopolarization, are negligible. Conversely, changes in DC conductivity with resin stoichiometry appear to occur as a result of changes in the chemical content of the system, rather than variations in network structure or dynamics. Specifically, we suggest that the DC conductivity is markedly affected by the residual amine group concentration in the system. While DC conductivity and DC breakdown appear broadly to be correlated, AC breakdown results indicated that this parameter does not vary with changing stoichiometry, which suggests that the AC and DC breakdown strengths are controlled by different mechanisms

The Effect of Water Absorption on the Dielectric Properties of Polyethylene Hexagonal Boron Nitride Nanocomposites

The effect of water absorption on the dielectric response of polyethylene/hexagonal boron nitride nanocomposites has been studied by dielectric spectroscopy. The nanocomposites have been prepared with hBN concentrations ranging from 2 wt% to 30 wt%. Fourier transform infrared spectroscopy and thermogravimetric analysis revealed a very small amount of hydroxyl groups on the surface of hBN. Mass loss measurements showed that the nanocomposites did not absorb any water under ambient and dry conditions while there was some water absorption under wet conditions. The dielectric spectroscopy results showed a broad relaxation peak, indicative of different states of water with water shells of different thickness, which moved to higher frequencies with increasing water content. However, the dielectric losses were significantly lower than the losses reported in the literature of nanocomposites under wet conditions. In addition, all the absorbed water was successfully removed under vacuum conditions which demonstrated that the interactions between the water and the nanocomposites were very weak, due to the hydrophobic nature of the hBN surface. This is a highly useful property, when considering these materials for applications in electrical insulation

Enhanced dielectric properties of polyethylene/hexagonal boron nitride nanocomposites

A range of nanocomposites based on a polyethylene polymer and hexagonal boron nitride (hBN) filler has been explored in this study. The dielectric properties of the nanocomposites, which consisted of 2 wt %, 5 wt %, 10 wt %, 20 wt %, and 30 wt % of hBN, have been compared to the dielectric properties of the unfilled polyethylene blend. Scanning electron microscopy (SEM) revealed that the hBN was uniformly distributed in the polyethylene matrix, although large amounts of agglomerates were present in the nanocomposites containing more than 10 wt % of hBN. The incorporation of hBN into polyethylene resulted in a highly disordered morphology in comparison to the unfilled polyethylene, in which this effect was more pronounced with increasing hBN content. This is consistent with the increasing crystallisation temperature as the hBN content increases, as shown by differential scanning calorimetry (DSC), where the hBN acted as a highly effective nucleating due to the strong interactions between the polyethylene and the hBN. This strong interaction is again reflected in the thermal decomposition temperature which similarly increases with increasing hBN content. The study demonstrates the remarkable electrical properties of the prepared nanocomposites, where the breakdown strength monotonically increased as a function of hBN content, even with a very high 30 wt % of hBN. The improvement in electrical properties, even at high hBN concentrations, is contradictory to the reported results in the literature and are mainly attributed to the hydrophobic surface of the hBN particles

Reclaiming the political : emancipation and critique in security studies

The critical security studies literature has been marked by a shared commitment towards the politicization of security – that is, the analysis of its assumptions, implications and the practices through which it is (re)produced. In recent years, however, politicization has been accompanied by a tendency to conceive security as connected with a logic of exclusion, totalization and even violence. This has resulted in an imbalanced politicization that weakens critique. Seeking to tackle this situation, the present article engages with contributions that have advanced emancipatory versions of security. Starting with, but going beyond, the so-called Aberystwyth School of security studies, the argument reconsiders the meaning of security as emancipation by making the case for a systematic engagement with the notions of reality and power. This revised version of security as emancipation strengthens critique by addressing political dimensions that have been underplayed in the critical security literature

Retrograde semaphorin-plexin signalling drives homeostatic synaptic plasticity.

Homeostatic signalling systems ensure stable but flexible neural activity and animal behaviour. Presynaptic homeostatic plasticity is a conserved form of neuronal homeostatic signalling that is observed in organisms ranging from Drosophila to human. Defining the underlying molecular mechanisms of neuronal homeostatic signalling will be essential in order to establish clear connections to the causes and progression of neurological disease. During neural development, semaphorin-plexin signalling instructs axon guidance and neuronal morphogenesis. However, semaphorins and plexins are also expressed in the adult brain. Here we show that semaphorin 2b (Sema2b) is a target-derived signal that acts upon presynaptic plexin B (PlexB) receptors to mediate the retrograde, homeostatic control of presynaptic neurotransmitter release at the neuromuscular junction in Drosophila. Further, we show that Sema2b-PlexB signalling regulates presynaptic homeostatic plasticity through the cytoplasmic protein Mical and the oxoreductase-dependent control of presynaptic actin. We propose that semaphorin-plexin signalling is an essential platform for the stabilization of synaptic transmission throughout the developing and mature nervous system. These findings may be relevant to the aetiology and treatment of diverse neurological and psychiatric diseases that are characterized by altered or inappropriate neural function and behaviour