445 research outputs found
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
- …