264 research outputs found
Fire Performance of Steel Reinforced Concrete (SRC) Structures
AbstractThis paper summarizes some of the recent research published on steel reinforced concrete (SRC) structures under or after exposure to fire. The contents include: 1) Fire resistance and post-fire behavior of SRC columns; 2) Fire performance of SRC column to beam joints, by adopting a loading sequence including initial loading, heating, cooling and post-fire loading; 3) Fire resistance and post-fire behavior of SRC composite frames
Analysis of concrete-filled stainless steel tubular columns under combined fire and loading
[EN] In fire scenarios, concrete-filled stainless steel tubular (CFSST) columns undergo initial loading at ambient temperature, loading during the heating phase as the fire develops, loading during the cooling phase as the fire dies out and continual loading after the fire. CFSST columns may fail some points during this process under combined fire and loading. In this paper, the failure modes and corresponding working mechanism of CFSST columns subjected to an entire loading and fire history are investigated. Sequentially coupled thermal-stress analyses in ABAQUS are employed to establish the temperature field and structural response of the CFSST column. To improve the precision of the finite element (FE) model, the influence of moisture on the thermal conductivity and specific heat of concrete during both the heating and cooling phases is considered using subroutines. Existing fire and post-fire test data of CFSST columns are used to validate the FE models. Comparisons between predicted and test results confirm that the accuracy of the FE models is acceptable; the FE models are then extended to simulate a typical CFSST column subjected to the entire loading and fire history. The behaviour of the CFSST column is explained by analysis of the temperature distribution, load versus axial deformation curves and failure response.The research reported in the paper is part of the Project 51308539 supported by the National
Natural Science Foundation of China. The financial support is highly appreciated.Tan, Q.; Gardner, L.; Han, L.; Song, D. (2018). Analysis of concrete-filled stainless steel tubular columns under combined fire and loading. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 825-833. https://doi.org/10.4995/ASCCS2018.2018.7206OCS82583
Differences in diversity and community assembly processes between planktonic and benthic diatoms in the upper reach of the Jinsha River, China
Comparing spatio-temporal patterns between planktonic and benthic algae is helpful for understanding their associations and differences. However, such studies are still rare especially in large rivers. We used a dataset collected in the upper reach of the Jinsha River in different seasons to explore biodiversity and assembly processes of planktonic and benthic diatom assemblages. We found that planktonic and benthic diatoms presented different seasonal variation in species richness and community compositions. We also found evidence that planktonic and benthic diatoms were coupled in the summer. Planktonic diatom assemblages were mainly affected by spatial processes via directional spatial dispersal, especially in the summer. By comparison, benthic diatom assemblages were more affected by environmental processes. Our findings suggest that mass effect and species sorting paradigms explain the assembly processes of planktonic and benthic diatom assemblages, respectively, but the explanatory powers of these two paradigms vary seasonally. To effectively monitor and assess ecological conditions of large rivers, we recommend using benthic algae as a biotic indicator group as they had stronger correlations with environmental factors.Peer reviewe
HOFA: Twitter Bot Detection with Homophily-Oriented Augmentation and Frequency Adaptive Attention
Twitter bot detection has become an increasingly important and challenging
task to combat online misinformation, facilitate social content moderation, and
safeguard the integrity of social platforms. Though existing graph-based
Twitter bot detection methods achieved state-of-the-art performance, they are
all based on the homophily assumption, which assumes users with the same label
are more likely to be connected, making it easy for Twitter bots to disguise
themselves by following a large number of genuine users. To address this issue,
we proposed HOFA, a novel graph-based Twitter bot detection framework that
combats the heterophilous disguise challenge with a homophily-oriented graph
augmentation module (Homo-Aug) and a frequency adaptive attention module
(FaAt). Specifically, the Homo-Aug extracts user representations and computes a
k-NN graph using an MLP and improves Twitter's homophily by injecting the k-NN
graph. For the FaAt, we propose an attention mechanism that adaptively serves
as a low-pass filter along a homophilic edge and a high-pass filter along a
heterophilic edge, preventing user features from being over-smoothed by their
neighborhood. We also introduce a weight guidance loss to guide the frequency
adaptive attention module. Our experiments demonstrate that HOFA achieves
state-of-the-art performance on three widely-acknowledged Twitter bot detection
benchmarks, which significantly outperforms vanilla graph-based bot detection
techniques and strong heterophilic baselines. Furthermore, extensive studies
confirm the effectiveness of our Homo-Aug and FaAt module, and HOFA's ability
to demystify the heterophilous disguise challenge.Comment: 11 pages, 7 figure
Three new shuttle vectors for heterologous expression in Zymomonas mobilis
Background: Zymomonas mobilis , as a novel platform for bio-ethanol
production, has been attractedmore attention and it is very important
to construct vectors for the efficient expression of foreign genes in
this bacterium. Results: Three shuttle vectors (pSUZM1, pSUZM2 and
pSUZM3)were first constructedwith the origins of replication from the
chromosome and two native plasmids (pZZM401 and pZZM402) of Z. mobilis
ZM4, respectively. The three shuttle vectorswere stable in Z. mobilis
ZM4 and have 3, 32 and 27 copies, respectively. The promoter Ppdc (a),
from the pyruvate decarboxylase gene,was cloned into the shuttle
vectors, generating the expression vectors pSUZM1(2, 3)a. The
codon-optimized glucoamylase gene from Aspergillus awamori combined
with the signal peptide sequence from the alkaline phosphatase gene of
Z. mobilis was cloned into pSUZM1(2, 3)a, resulting in the plasmids
pSUZM1a-GA, pSUZM2a-GA and pSUZM3a-GA, respectively. After transforming
these plasmids into Z. mobilis ZM4, the host was endowed with
glucoamylase activity for starch hydrolysis. Both pSUZM2a-GA and
pSUZM3a-GA were more efficient at producing glucoamylase than
pSUZM1a-GA. Conclusions: These results indicated that these
expression vectors are useful tools for gene expression in Z. mobilis
and this could provide a solid foundation for further studies of
heterologous gene expression in Z. mobilis
CO-CHANGES I: IRAM 30m CO Observations of Molecular Gas in the Sombrero Galaxy
Molecular gas plays a critical role in explaining the quiescence of star
formation (SF) in massive isolated spiral galaxies, which could be a result of
either the low molecular gas content and/or the low SF efficiency. We present
IRAM 30m observations of the CO lines in the Sombrero galaxy (NGC~4594), the
most massive spiral at . We detect at least one of the
three CO lines covered by our observations in all 13 observed positions located
at the galactic nucleus and along a -diameter dusty ring. The
total extrapolated molecular gas mass of the galaxy is . The measured maximum CO gas rotation
velocity of suggests that NGC~4594 locates in a dark
matter halo with a mass . Comparing to
other galaxy samples, NGC~4594 is extremely gas poor and SF inactive, but the
SF efficiency is apparently not inconsistent with that predicted by the
Kennicutt-Schmidt law, so there is no evidence of enhanced SF quenching in this
extremely massive spiral with a huge bulge. We also calculate the predicted gas
supply rate from various sources to replenish the cold gas consumed in SF, and
find that the galaxy must experienced a starburst stage at high redshift, then
the leftover or recycled gas provides SF fuels to maintain the gradual growth
of the galactic disk at a gentle rate.Comment: 21 pages, 13 figures, accepted for publication in MNRA
Excited state biexcitons in atomically thin MoSe2
The tightly bound biexcitons found in atomically thin semiconductors have very promising applications for optoelectronic and quantum devices. However, there is a discrepancy between theory and experiment regarding the fundamental structure of these biexcitons. Therefore, the exploration of a biexciton formation mechanism by further experiments is of great importance. Here, we successfully triggered the emission of biexcitons in atomically thin MoSe2, via the engineering of three critical parameters: dielectric screening, density of trions, and excitation power. The observed binding energy and formation dynamics of these biexcitons strongly support the model that the biexciton consists of a charge attached to a trion (excited state biexciton) instead of four spatially symmetric particles (ground state biexciton). More importantly, we found that the excited state biexcitons not only can exist at cryogenic temperatures but also can be triggered at room temperature in a freestanding bilayer MoSe2. The demonstrated capability of biexciton engineering in atomically thin MoSe2 provides a route for exploring fundamental many-body interactions and enabling device applications, such as bright entangled photon sources operating at room temperature
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