scholarly journals Numerical Simulation and Experimental Investigation of the Preparation of Aluminium Alloy 2A50 Semi-Solid Billet by Electromagnetic Stirring

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5470
Author(s):  
Yongfei Wang ◽  
Shengdun Zhao ◽  
Yi Guo
Keyword(s):  
Numerical Simulation ◽  
Aluminium Alloy ◽  
Deep Understanding ◽  
Electromagnetic Stirring ◽  
Experimental Result ◽  
Maximum Speed ◽  
Operating Parameters ◽  
Average Grain Size ◽  
Semi Solid ◽  
High Level

Electromagnetic stirring (EMS) has become one of the most important branches of the electromagnetic processing of materials. However, a deep understanding of the influence of the EMS on the thermo-fluid flow of the aluminium alloy melt, and consequently the refinement of the microstructure is still not available. This paper investigated the influence of the operating parameters of EMS on the magnetohydrodynamics, temperature field, flow field, and the vortex-shaped structure of the melt as well as the microstructure of the aluminium alloy 2A50 billet by numerical simulation and experiments. The operating parameters were categorised into three groups representing high, medium, and low levels of Lorentz forces generated by EMS. The numerical simulation matched well with the experimental result. It was found that a high level of EMS can improve the uniformity of the temperature and flow fields. The maximum speed was observed at the radius of around 25 mm under all EMS levels. Both the depth and diameter of the vortex-shaped structure generated increased with the enhancement in the EMS level. The average grain size of the edge sample of the billet was reduced by 48.3% while the average shape factor was increased by 51.0% under the medium-level EMS.

Preparation of 2A14 Aluminium Alloy Large-Sized Hollow Ingots by Electromagnetic Stirring DC Casting

2020 ◽  
Vol 993 ◽  
pp. 267-272
Author(s):  
Xiao Peng Li ◽  
Bao Li ◽  
Zhi Hua Gao ◽  
Tian Yang Guan ◽  
Ming Wei Gao ◽  
...  
Keyword(s):  
Grain Size ◽  
Aluminium Alloy ◽  
Grain Morphology ◽  
Electromagnetic Stirring ◽  
Middle Section ◽  
Negative Segregation ◽  
Fine Grain ◽  
Average Grain Size ◽  
Dc Casting ◽  
Positive Segregation

The Φ730 / Φ340 mm hollow ingots of 2A14 aluminium alloy were produced by conventional and electromagnetic stirring (EMS) DC casting with extremely fine grain morphology. The results indicate that the metallographic microstructure of the alloy was more uniform and homogeneous in the EMS hollow ingot and the finer grain size was obtained. The average grain size dramatically decreased from 115 μm to 70 μm with applying EMS. The macrosegregation patterns of Cu element in EMS and conventional hollow ingots along the radial direction were both following the similar trend that positive segregation occurred in inner subsurface and middle section. Meanwhile negative segregation occurred in section offset to inside of centerline and outer surface. The extent of macrosegregation in EMS hollow ingot was severer than that in the conventional one. The mechanism of EMS was discussed to reveal its effect on the microstructure and macrosegregation.

Microstructure Evolution of Conventional and Semi-Solid Cast of A356 Aluminium Alloy with Addition of Inoculant

2015 ◽  
Vol 819 ◽  
pp. 25-30 ◽  
Author(s):  
M.N. Laila Masrur ◽  
M. Syukron ◽  
H. Zuhailawati ◽  
A.S. Anasyida
Keyword(s):  
Aluminium Alloy ◽  
Dendritic Structure ◽  
A356 Alloy ◽  
Optical Microscope ◽  
Globular Structure ◽  
Average Grain Size ◽  
Semi Solid ◽  
Vicker’S Microhardness ◽  
Steel Mould ◽  
A356 Aluminium Alloy

This paper investigated the effect of inoculant, Al-5Ti-1B in conventional and semi-solid casting A356 aluminium alloy. A356 aluminium alloy was melted at 850 oC and poured at 680 °C directly into the steel mould and on the inclined slope into steel mould. Inoculant was added in various percentages of 1 wt.%, 2 wt.%, 3 wt.% and 3.5 wt.% in A356 aluminium alloy melt. Microstructure and microhardness were characterized using optical microscope and Vicker’s microhardness tester. The addition of master alloy up 3.5 wt.% Al-5Ti-1B in conventional casting refined dendritic structure with average grain size of 33.41 μm. The microstructures of semi-solid A356 aluminium alloy with addition of Al-5Ti-1B consist of equiaxed structure of α-Al. Further addition of Al-5Ti-1B refined the globular structure of α-Al. The higher hardness was achieved for A356 alloy prepared using semi-solid with addition of 3.5 wt.% of Al-5Ti-1B.

HALIMA KHUDAYBERDIEVA POETRY MASTERY TO USE SYMBOLS AND IMAGES

2020 ◽  
Vol 3 (3) ◽  
pp. 49-52
Author(s):  
Mehrinoz Abbosova ◽  
Keyword(s):  
Deep Understanding ◽  
Artistic Representations ◽  
High Level ◽  
Main Factor

The article deals with the skill of using symbols and emblems in the poetry of the poetess Halima Khudaiberdieva. Poetry is one of the highest forms of art, and its perception requires a high level,high taste, deep understanding from the reader. The article lists important aspects of the requirements for an original poem. It is emphasized that the main factor of mystery in the poem are symbols and allusions. Some examples from the poems of the poet are given and analyzed. Through this, an attempt was made to explore the artistic representations of the poet’s poetry

Numerical Simulation on Mold Electromagnetic Eccentric Stirring and Central Segregation of Round Bloom

2013 ◽  
Vol 652-654 ◽  
pp. 2450-2454
Author(s):  
Zhi Hong Zhang ◽  
Guo Guang Cheng
Keyword(s):  
Numerical Simulation ◽  
Mathematical Model ◽  
Electromagnetic Stirring ◽  
Center Line ◽  
Central Segregation

The paper describes multi-section round bloom casting using external MEMS, equipped with max section D600mm and min D280mm mold, the center line of D280mm mold not coincident with the axis of stirrer coils. it is exist eccentric electromagnetic stirring of mold which section less than max D600mm, a mathematical model of MEMS has been established, the index of central segregation of D280mm macrostructure had decreased less than 1.12 by optimized parameters of electromagnetic stirring and SEN immerse depth, in the end, the quality of round bloom had improved.

A Reflexive Approach to Teaching Writing: Enablements and Constraints in Primary School Classrooms

2021 ◽  
pp. 074108832110055
Author(s):  
Mary Ryan ◽  
Maryam Khosronejad ◽  
Georgina Barton ◽  
Lisa Kervin ◽  
Debra Myhill
Keyword(s):  
Time Management ◽  
Deep Understanding ◽  
Writing Pedagogy ◽  
Teacher Talk ◽  
Teaching Writing ◽  
Writing Teachers ◽  
Teacher Interview ◽  
Approach To Teaching ◽  
High Level ◽  
Teaching Of Writing

Writing requires a high level of nuanced decision-making related to language, purpose, audience, and medium. Writing teachers thus need a deep understanding of language, process, and pedagogy, and of the interface between them. This article draws on reflexivity theory to interrogate the pedagogical priorities and perspectives of 19 writing teachers in primary classrooms across Australia. Data are composed of teacher interview transcripts and nuanced time analyses of classroom observation videos. Findings show that teachers experience both enabling and constraining conditions that emerge in different ways in different contexts. Enablements include high motivations to teach writing and a reflective and collaborative approach to practice. However, constraints were evident in areas of time management, dominance of teacher talk, teachers’ scope and confidence in their knowledge and practice, and a perceived lack of professional support for writing pedagogy. The article concludes with recommendations for a reflexive approach to managing these emergences in the teaching of writing.

Semantic Relation Model and Dataset for Remote Sensing Scene Understanding

2021 ◽  
Vol 10 (7) ◽  
pp. 488
Author(s):  
Peng Li ◽  
Dezheng Zhang ◽  
Aziguli Wulamu ◽  
Xin Liu ◽  
Peng Chen
Keyword(s):  
Remote Sensing ◽  
Scene Understanding ◽  
Deep Understanding ◽  
Remote Sensing Images ◽  
Convolutional Network ◽  
Scene Graph ◽  
Multi Scale ◽  
Relationship Extraction ◽  
High Level ◽  
Graph Generation

A deep understanding of our visual world is more than an isolated perception on a series of objects, and the relationships between them also contain rich semantic information. Especially for those satellite remote sensing images, the span is so large that the various objects are always of different sizes and complex spatial compositions. Therefore, the recognition of semantic relations is conducive to strengthen the understanding of remote sensing scenes. In this paper, we propose a novel multi-scale semantic fusion network (MSFN). In this framework, dilated convolution is introduced into a graph convolutional network (GCN) based on an attentional mechanism to fuse and refine multi-scale semantic context, which is crucial to strengthen the cognitive ability of our model Besides, based on the mapping between visual features and semantic embeddings, we design a sparse relationship extraction module to remove meaningless connections among entities and improve the efficiency of scene graph generation. Meanwhile, to further promote the research of scene understanding in remote sensing field, this paper also proposes a remote sensing scene graph dataset (RSSGD). We carry out extensive experiments and the results show that our model significantly outperforms previous methods on scene graph generation. In addition, RSSGD effectively bridges the huge semantic gap between low-level perception and high-level cognition of remote sensing images.

Countering Threats

2014 ◽  
Vol 4 (2) ◽  
pp. 35-45
Author(s):  
Margarita Jaitner
Keyword(s):  
Social Media ◽  
Law Enforcement ◽  
Ad Hoc ◽  
Physical Violence ◽  
Deep Understanding ◽  
Current Status ◽  
Mobile Web ◽  
Use Of Social Media ◽  
Legal Frameworks ◽  
High Level

The increased adoption of social media has presented security and law enforcement authorities with significant new challenges. For example, the Swedish Security Service (SÄPO) asserts that a large proportion of radicalization takes place in open fora online. Still, approaches to contain social media-driven challenges to security, particularly in democratic societies, remain little explored. Nonetheless, this type of knowledge may become relevant in European countries in the near future: Amongst other factors, the challenging economic situation has resulted in increased public discontent leading to emergence or manifestation of groups that seek to challenge the existing policies by almost any means. Use of social media multiplies the number of vectors that need law enforcement attention. First, a high level of social media adaption allows groups to reach and attract a wider audience. Unlike previously, many groups today consist of a large but very loosely connected network. This lack of cohesion can present a challenge for authorities, to identify emerging key actors and assess threat levels. Second, a high level of mobile web penetration has allowed groups to ad-hoc organize, amend plans and redirect physical activities. Third, the tool social media is as not exclusive to potential perpetrators of unlawful action, but is as well available to law enforcement authorities. Yet, efficient utilization of social media requires a deep understanding of its nature and a well-crafted, comprehensive approach. Acknowledging the broad functionality of social media, as well as its current status in the society, this article describes a model process for security authorities and law enforcement work with social media in general and security services work in particular. The process is cyclic and largely modular. It provides a set of goals and tasks for each stage of a potential event, rather than fixed activities. This allows authorities to adapt the process to individual legal frameworks and organization setups. The approach behind the process is holistic where social media is regarded as both source and destination of information. Ultimately, the process aims at efficiently and effectively mitigating the risk of virtual and physical violence.

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