Fire responses and resistance of concrete-filled steel tubular frame structures

This paper presents the results of dynamic responses and fire resistance of concretefilled steel tubular (CFST) frame structures in fire conditions by using non-linear finite element method. Both strength and stability criteria are considered in the collapse analysis. The frame structures are constructed with circular CFST columns and steel beams of I-sections. In order to validate the finite element solutions, the numerical results are compared with those from a fire resistance test on CFST columns. The finite element model is then adopted to simulate the behaviour of frame structures in fire. The structural responses of the frames, including critical temperature and fire-resisting limit time, are obtained for the ISO-834 standard fire. Parametric studies are carried out to show their influence on the load capacity of the frame structures in fire. Suggestions and recommendations are presented for possible adoption in future construction and design of these structures

A unified formulation for circle and polygon concrete-filled steel tube columns under axial compression

Current design practice of concrete-filled steel tube (CFST) columns uses different formulas for different section profiles to predict the axial load bearing capacity. It has always been a challenge and practically important issue for researchers and design engineers who want to find a unified formula that can be used in the design of the columns with various sections, including solid, hollow, circular and polygonal sections. This has been driven by modern design requirements for continuous optimization of structures in terms of not only the use of materials, but also the topology of structural components. This paper extends the authors’ previous work [1] on a unified formulation of the axial load bearing capacity for circular hollow and solid CFST columns to, now, including hollow and solid CFST columns with regular polygonal sections. This is done by taking a circular section as a special case of a polygonal one. Finally, a unified formula is proposed for calculating the axial load bearing capacity of solid and hollow CFST columns with either circular or polygonal sections. In addition, laboratory tests on hollow circular and square CFST long columns are reported. These results are useful addition to the very limited open literature on testing these columns, and are also as a part of the validation process of the proposed analytical formulas

Improved mechanical and electrical properties in electrospun polyimide/multiwalled carbon nanotubes nanofibrous composites

Highly aligned polyimide (PI) and PI/multi-walled carbon nanotubes (PI/MWCNTs) nanofibrous composites by incorporating poly(ethylene oxide) as the dispersing medium were fabricated using electrospinning technique. The morphology, mechanical, and electrical properties of the electrospun nanofibrous composites were investigated. Scanning electron microscope showed that the functionalized MWCNTs (f-MWCNTs) were well dispersed and oriented along the nanofiber axis. Analysis of electrical properties indicated a remarkable improvement on the alternating current conductivity by introduction of the aligned f-MWCNTs. Besides, with addition of 3 vol.% f-MWCNTs, the obvious enhancement of tensile modulus and strength was achieved. Thus, the electrospun PI/MWCNTs nanofibrous composites have great potential applications in multifunctional engineering materials

A genuine four-partite entangled state

In a recent paper, a genuine four-partite entangled state is proposed [Y. Yeo and W. K. Chua, Phys. Rev. Lett. 96, 060502 (2006)], which has been found to have many interesting entanglement properties. We show this state is locally equivalent to some graph states.Comment: submitte

Cytotoxic and genotoxic effects of perfluorododecanoic acid (PFDoA) in Japanese medaka

This study investigated the cytotoxic and genotoxic potential of perfluorododecanoic acid (PFDoA), a perfluorinated carboxylic chemical (PFC) that has broad applications and distribution in the environment in Japanese medaka, Oryzias latipes. Micronucleus (MN) test and Comet assay were used for the toxicity study. Three groups of fish were exposed to 0.1 mg/L, 0.5mg/L and 2.5mg/L concentration of the chemical for 28 days.Another group served as control. Sampling of the fish blood and liverwere done after days 1, 4, 7, 14, 21 and 28 for analysis of different erythrocyte abnormalities and damage to DNA using the MN test and Comet assay respectively. Results showed that there was a significant time and concentration dependent increase (p<0.05) in percent tail length of DNA and frequency of erythrocyte abnormalities. Nuclear abnormalities observed include micronucleus, fragmented apoptotic cells, lobed nuclei, and bean-shaped cells. Increase in induction of erythrocyte abnormalities and percent tail length of DNA peaked at days 14 and 7,respectively, after which there was a gradual decline. The results indicate that sub-chronic exposure of PFDoA to Japanese medaka caused DNA damage with a simultaneous induction of different erythrocyte abnormalities

The influence of joints and composite floor slabs on effective tying of steel structures in preventing progressive collapse

The event of the terrorist attack at 11th September 2001 in the USA has attracted increasing attention of researchers and engineers on progressive collapse of structures. It has gradually become a general practice for engineers to consider progressive collapse resistance in their design. In this paper, progressive collapse of steel frames with composite floor slabs is simulated by the finite element method. The numerical results are compared with test results. The influence of the joints and the concrete slabs on the effective tying of steel beams is investigated through parametric studies. From the analysis, methods of preventing progressive collapse that can be considered in design and when retrofitting existing structures are proposed. The results show that retrofitting a structure with pre-stressed steel cables and an increase of crack resistance in the concrete near joints can effectively improve effective tying of a structure, which results in an enhanced structural capacity in preventing progressive collapse

A Two-Stream Mutual Attention Network for Semi-supervised Biomedical Segmentation with Noisy Labels

\begin{abstract} Learning-based methods suffer from a deficiency of clean annotations, especially in biomedical segmentation. Although many semi-supervised methods have been proposed to provide extra training data, automatically generated labels are usually too noisy to retrain models effectively. In this paper, we propose a Two-Stream Mutual Attention Network (TSMAN) that weakens the influence of back-propagated gradients caused by incorrect labels, thereby rendering the network robust to unclean data. The proposed TSMAN consists of two sub-networks that are connected by three types of attention models in different layers. The target of each attention model is to indicate potentially incorrect gradients in a certain layer for both sub-networks by analyzing their inferred features using the same input. In order to achieve this purpose, the attention models are designed based on the propagation analysis of noisy gradients at different layers. This allows the attention models to effectively discover incorrect labels and weaken their influence during the parameter updating process. By exchanging multi-level features within the two-stream architecture, the effects of noisy labels in each sub-network are reduced by decreasing the updating gradients. Furthermore, a hierarchical distillation is developed to provide more reliable pseudo labels for unlabelded data, which further boosts the performance of our retrained TSMAN. The experiments using both the HVSMR 2016 and BRATS 2015 benchmarks demonstrate that our semi-supervised learning framework surpasses the state-of-the-art fully-supervised results