777 research outputs found
A Semantic Graph-Based Approach for Mining Common Topics From Multiple Asynchronous Text Streams
In the age of Web 2.0, a substantial amount of unstructured
content are distributed through multiple text streams in an
asynchronous fashion, which makes it increasingly difficult
to glean and distill useful information. An effective way to
explore the information in text streams is topic modelling,
which can further facilitate other applications such as search,
information browsing, and pattern mining. In this paper, we
propose a semantic graph based topic modelling approach
for structuring asynchronous text streams. Our model in-
tegrates topic mining and time synchronization, two core
modules for addressing the problem, into a unified model.
Specifically, for handling the lexical gap issues, we use global
semantic graphs of each timestamp for capturing the hid-
den interaction among entities from all the text streams.
For dealing with the sources asynchronism problem, local
semantic graphs are employed to discover similar topics of
different entities that can be potentially separated by time
gaps. Our experiment on two real-world datasets shows that
the proposed model significantly outperforms the existing
ones
Development of a Respirable Dust Mitigation System for a High Longwall Face at Sihe Colliery in China â a Case Study
Dust is a major hazard in underground coal mines that threatens the work health and safety of coal miners. The dust issue becomes increasingly significant with the development of highly mechanized coal mining. This issue is particularly serious at the high longwall faces of the Sihe colliery in China as the concentration of dust, in particular respirable dust, at these faces far exceeds the regulatory dust limits. Field testing and computational fluid dynamics (CFD) simulations were conducted to understand the sources of dust generation and its dynamic movement in the #5301 longwall face of high-cutting height at the colliery. The investigation results showed that shearer generated dust was minimal during the coal cutting operation; that face spalling and chock movement were the main dust generating sources, causing significant contamination to the walkway; and that the majority of dust particles from the face (regardless of source) eventually disperse into the main gate, where the dust concentration was greater than 500 mg/m3. These findings were used to develop an effective coal dust mitigation system involving the installation of dust scrubbers, curtains, and venture and crescent sprays. The results of CFD modeling indicate that the dust concentration could be significantly reduced by adopting the new dust mitigation system
A holistic review on fatigue properties of additively manufactured metals
Additive manufacturing (AM) technology is undergoing rapid development and
emerging as an advanced technique that can fabricate complex near-net shaped
and light-weight metallic parts with acceptable strength and fatigue
performance. A number of studies have indicated that the strength or other
mechanical properties of AM metals are comparable or even superior to that of
conventionally manufactured metals, but the fatigue performance is still a
thorny problem that may hinder the replacement of currently used metallic
components by AM counterparts when the cyclic loading and thus fatigue failure
dominates. This article reviews the state-of-art published data on the fatigue
properties of AM metals, principally including -- data and fatigue crack
growth data. The AM techniques utilized to generate samples in this review
include powder bed fusion (e.g., EBM, SLM, DMLS) and directed energy deposition
(e.g., LENS, WAAM). Further, the fatigue properties of AM metallic materials
that involve titanium alloys, aluminum alloys, stainless steel, nickel-based
alloys, magnesium alloys, and high entropy alloys, are systematically
overviewed. In addition, summary figures or tables for the published data on
fatigue properties are presented for the above metals, the AM techniques, and
the influencing factors (manufacturing parameters, e.g., built orientation,
processing parameter, and post-processing). The effects of build direction,
particle, geometry, manufacturing parameters, post-processing, and
heat-treatment on fatigue properties, when available, are provided and
discussed. The fatigue performance and main factors affecting the fatigue
behavior of AM metals are finally compared and critically analyzed, thus
potentially providing valuable guidance for improving the fatigue performance
of AM metals.Comment: 201 pages, 154 figure
Driving Risk Detection Model of Deceleration Zone in Expressway Based on Generalized Regression Neural Network
Drivers’ mistakes may cause some traffic accidents, and such accidents can be avoided if prompt advice could be given to drivers. So, how to detect driving risk is the key factor. Firstly, the selected parameters of vehicle movement are reaction time, acceleration, initial speed, final speed, and velocity difference. The ANOVA results show that the velocity difference is not significant in different driving states, and the other four parameters can be used as input variables of neural network models in deceleration zone of expressway, which have fifteen different combinations. Then, the detection model results indicate that the prediction accuracy rate of testing set is up to 86.4%. An interesting finding is that the number of input variables is positively correlated with the prediction accuracy rate. By applying the method, the dangerous state of vehicles could be released through mobile internet as well as drivers' start of risky behaviors, such as fatigue driving, drunk driving, speeding driving, and distracted driving. Numerical analyses have been conducted to determine the conditions required for implementing this detection method. Furthermore, the empirical results of the present study have important implications for the reduction of crashes.
Document type: Articl
Development of a Respirable Dust Mitigation System for a High Longwall Face at Sihe Colliery in China – a Case Study
Dust is a major hazard in underground coal mines that threatens the work health and safety of coal miners. The dust issue becomes increasingly significant with the development of highly mechanized coal mining. This issue is particularly serious at the high longwall faces of the Sihe colliery in China as the concentration of dust, in particular respirable dust, at these faces far exceeds the regulatory dust limits. Field testing and computational fluid dynamics (CFD) simulations were conducted to understand the sources of dust generation and its dynamic movement in the #5301 longwall face of high-cutting height at the colliery. The investigation results showed that shearer generated dust was minimal during the coal cutting operation; that face spalling and chock movement were the main dust generating sources, causing significant contamination to the walkway; and that the majority of dust particles from the face (regardless of source) eventually disperse into the main gate, where the dust concentration was greater than 500 mg/m3. These findings were used to develop an effective coal dust mitigation system involving the installation of dust scrubbers, curtains, and venture and crescent sprays. The results of CFD modeling indicate that the dust concentration could be significantly reduced by adopting the new dust mitigation system
Baicalein mediates inhibition of migration and invasiveness of skin carcinoma through Ezrin in A431 cells
<p>Abstract</p> <p>Background</p> <p>Ezrin is highly expressed in skin cancer and promotes tumor metastasis. Ezrin serves as a promising target for anti-metastasis therapy. The aim of this study is to determine if the flavonoid bacailein inhibits the metastasis of skin cancer cells through Ezrin.</p> <p>Methods</p> <p>Cells from a cutaneous squamous carcinoma cell line, A431, were treated with baicalein at 0-60 μM to establish the non-cytotoxic concentration (NCC) range for baicalein. Following treatment with baicalein within this range, total Ezrin protein (both phosphorylated and unphosphorylated forms) and phosphorylated-Ezrin (phos-Ezrin) were detected by western blotting, and Ezrin RNA was detected in A431 cells using reverse transcription-polymerase chain reaction (RT-PCR). Thereafter, the motility and invasiveness of A431 cells following baicalein treatment were determined using wound-healing and Boyden chamber invasion assays. Short-interfering RNA (si-RNA) specifically targeting Ezrin was transfected into A431 cells, and a si-RNA Ezrin-A431 cell line was established by G418 selection. This stable cell line was transiently transfected with Ezrin and mutant Ezrin plasmids, and its motilityand invasiveness was subsequently determined to clarify whether bacailein inhibits these processes through Ezrin.</p> <p>Results</p> <p>We determined the range of NCCs for baicalein to be 2.5-40 μM in A431 cells. Baicalein displayed a dose- and time-dependent inhibition of expressions of total Ezrin and phos-Ezrin within this range NCCs. In addition, it exerted this inhibitory effect through the reduction of Ezrin RNA transcript. Baicalein also inhibited the motility and invasiveness of A431 skin carcinoma cells within the range of NCCs, in a dose- and time-dependent manner. A431 cell motility and invasiveness were inhibited by 73% and 80% respectively when cells were treated with 20 μM baicalein. However, the motility and invasiveness of A431 cells containing the Ezrin mutant were not effectively inhibited by baicalein.</p> <p>Conclusions</p> <p>Baicalein reduces the migration and invasiveness of A431 cells through the inhibition of Ezrin expression, which leads to the suppression of tumor metastasis.</p
A new flywheel energy storage system for distributed generation
ABSTRACT It is necessary to install flywheel energy storage (FES) system in distributed generation, which can improve the quality and the reliability of electric power. The proposed system is composed of four parts: flywheel, magnetic bearing, motor/generator, and power converter. A permanent magnet motor-generator is incorporated in a composite flywheel, running at high speed in a vacuum containment to minimize air friction losses. The flywheel is to be suspended on magnet bearings. A 3-phase, switch mode bridge inverter, driven by a pulse width modulation board, achieves the variable speed control for the motor/generator and the control for the DC bus voltage. The presentation will explain the schematics of the flywheel battery, control diagram, power electronics and motor/generator. The overall operation will be described
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