644 research outputs found
Study on martensitic transformation twinning in ductile metastable body-centered-cubic high entropy alloys
No full textMartensitic transformation twinning including {111}α’’ type I, ‘‘{351}’’< 2‾11 >α’’ type II and {021}α’’ twins, and extrinsic {111}α’’ stacking faults were investigated in a deformed body-centered-cubic (BCC) high entropy alloy (HEA). The interaction between martensitic twinning and local chemical environment variation made great contributions to strain accommodation upon straining, implying a novel route to develop ductile BCC HEAs
Influence of tantalum composition on mechanical behavior and deformation mechanisms of TiZrHfTa<sub>x</sub> high entropy alloys
No full textThe effects of metastability engineering on tuning deformation behavior and deformation mechanisms in TiZrHfTa
X (x = 1.00, 0.80, 0.60, 0.50) refractory body-centered cubic (BCC) high entropy alloys were investigated, with specific emphasis on elucidating the underlying interplay between phase stability, mechanical property, and deformation twins. It was found that in proper thermomechanical treated samples, a variation of tantalum content can effectively tune the activation of various deformation mechanisms. Detailed electron back-scattered diffraction and transmission electron microscopy analyses revealed for the first time that {332}<113̅>
BCC twinning, deformation-induced α’’ phase, {111}
α’’ type I and <2̅11>
α’’ type II twinning can be sequentially activated in TiZrHfTa
X (x = 1.00, 0.80, 0.60, 0.50) high entropy alloys with decreasing the content of tantalum. The comprehensive strengthening effect of transformation induced plasticity and twinning induced plasticity, was discussed and attributed as the pivotal factor for the improved work hardening capability and mechanical performances, especially for alloys with lower tantalum contents. Consequently, we extended the conventional bond order and d‐orbital energy level diagram that was originally developed for body-centered cubic titanium alloys for deformation mechanism evaluation to body-centered cubic high entropy alloys on the basis of current results, which sheds light on the design of ductile body-centered cubic high entropy alloys with expected deformation mechanisms and optimized mechanical performance.
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Multiscale Model Reduction and Learning
Full text linkMany engineering problems have multiscale features. These problems usually require some model reduction since the computational cost of a fine-scale solution is extremely expensive. Existing model reduction methods such as Generalized Multiscale Finite Element Method (GMsFEM) and Non-local multi-continuum approach (NLMC) have shown extensive success in solving multiscale problems especially on various flow simulation problems.
However, there are still challenges in developing effective multiscale models for flow in more complicated heterogeneous media. The geometries of domain, coexistence of multiple continuum, and lack of observation data can all give rise to the difficulty of developing the reduced-order model. In this thesis, I will concentrate on the development of novel multiscale methods following the idea of the existing model reduction methods to address such problems. Moreover, deep learning techniques are combined to overcome certain difficulties met along model construction. These proposed models are targeted to tackle specific problems, where the performance is verified both numerically and analytically.
For instance, flow simulation within a heterogeneous thin domain is one of such challenging problems. Though homogenization methods are proven to be successful when the media have clear scale separation, that���s not always the case for flow simulation within a capillary system. Using only one basis function in each coarse region can lead to large errors. We thus design a customized GMsFEM instead, which is able to automatically enrich the approximation space and significantly reduce the error.
When simulating flow in a fractured vuggy reservoir, on the other hand, I develop a coarse solver under the framework of GMsFEM by combining it with multi-continuum model and Discrete Fracture Model (DFM). Instead of treating the media as a single continuum, I treat the multiscale formation hierarchically and consider it as a coupled system of matrix, fractures and vugs. This allows us to explicitly represent the mass transfers between continuum as well as model the local effects of the discrete fractures.
We further investigate how deep learning can facilitate multiscale model construction for nonlinear flow dynamics. Utilizing a multi-layer neural network to approximate the reduced order model, the observed data can be easily incorporated to adjust the model. Deep learning techniques are also used to conduct model reduction. With a soft thresholding operator as an activation function, a novel neural network is proposed which can identify important multiscale features that are crucial in modeling the underlying flow. The forward input-output maps are thus learned in a reduced way.
Extensive applications to engineering problems and numerical analysis are presented in supplement of the proposed approaches. It is shown that our proposed methods can significantly advance the computational efficiency and accuracy for multiscale flow simulation in various heterogeneous media
The population vicariance of Stentor coeruleus in Lake Donghu, Wuhan
No full textRandom amplified polymorphic DNA( RAPD) markers were applied to analyze genetic relationships of Stentor coeruleus that were sampled from four water areas including Lake Donghu (D. Lake), Lake Nanhu (N. Lake), Lake Yuehu (Y. Lake) and Pond Guanqiao (G. Pond). Their Genomes were amplified with 12 random primers. Distinctly different banding patterns were obtained, with which the genetic relationship of organisms treated was deduced: the genetic distance among the sample was 0.076-0.416. The phylogenetic tree was constructed by Rapdistance 1.04. The results showed that three samples from N. Lake clustered into one branch which indicated S. coeruleus in the lake belong to one population, but 3 samples from D. Lake were separated by the sample from G. Pond which showed that S. coeruleus in it belong to different populations. This discovery supported the hypothesis of vicariance in geographic. It will promote the researches on the population ecology of micro-hydrobiont, and the development of phylogeography and vicariance biogeography
Misdiagnosis of Systemic Lupus Erythematosus Combined with Urinary Tuberculosis Leading to Tuberculous Meningitis: A Case Report and Literature Review
No full textHonglei Ma,1 Yuqun Wang,1 Junhong Liu,1 Linping Du,1 Xiaodong Wang,2 Yingliang Wang2 1Affiliated Hospital of Weifang Medical University, School of Clinical Medicine, Weifang Medical University, Weifang, Shandong Province, People’s Republic of China; 2Rheumatology and Immunology, Affiliated Hospital of Weifang Medical University, Weifang, Shandong Province, People’s Republic of ChinaCorrespondence: Yingliang Wang, Affiliated Hospital of Weifang University, No. 2428, Yuhe Road, Kuiwen District, Weifang, Shandong Province, People’s Republic of China, Tel +86 13869663571, Fax +86 5363081201, Email [email protected]: To explore the lessons learned from the misdiagnosis of systemic lupus erythematosus (SLE) combined with urinary tuberculosis leading to tuberculous meningitis (TBM) and the diagnosis and treatment of TBM through case reports and review of the literature.Methods: We report a case of an SLE patient presenting with urinary tuberculosis infection misdiagnosed as interstitial cystitis and complex urinary tract infection, who developed neurological infection after a cystocentesis biopsy and was eventually diagnosed with TBM. In addition, all cases of SLE combined with TBM from January 1975 to February 2022 were summarised and reviewed to compare current diagnostic and treatment strategies for the disease.Results: The patient suddenly developed neurological symptoms after cystocentesis biopsy, and we detected Mycobacterium tuberculosis in the macrogenomic next-generation sequence (mNGS) of the cerebrospinal fluid. We therefore excluded interstitial cystitis and neuropsychiatric lupus to confirm the diagnosis of Mycobacterium tuberculosis infection leading to urinary tract tuberculosis and TBM.Conclusion: SLE is complicated by urological tuberculosis, surgery triggering hematogenous dissemination leading to tuberculous meningitis. At the same time, the lack of specificity in the clinical presentation of patients makes it easy to misdiagnose neuropsychiatric lupus and delay treatment, so timely and accurate diagnosis and effective anti-tuberculosis treatment are essential.Keywords: tuberculosis, meningeal, urinary tuberculosis, lupus erythematosus, systemic, lupus vasculitis, central nervous syste
The Application of Bourdieu’s Theory: Challenges faced by Master Chinese International Students during the Capital Conversion
No full textThis essay is divided into five sections. The first section is a brief introduction about this essay. It points out the theory employed by the author and introduces the research background, the research significance and the essay’s structure. In the second part, the author provides a description about what Master Chinese international students face in the British university. The third part gives a literature review about Bourdieu’s Theory: capital, habitus and field. In the next section, the previous mentioned theory will be applied to the Master Chinese student in the UK university, and the author will analyse it. At last, the conclusion will be presented
Isolation of Native-Like Lignin
No full textThe isolation of lignin with a native-like structure plays an essential role in studying the structure and chemistry of lignin leading to an enhanced understanding of the fate of lignin during the processing of lignocellulosic biomass. In this chapter, we provide a practical overview of methodologies to extract lignin with a native-like structure. This overview starts from more traditional methods such as Braun's lignin and proceeds to more recently developed methods using alternative solvents and flow-through setups. Step-by-step procedures are provided as well as critical steps within these are discussed. Also, more recent extraction methods that modify the lignin β-O-4 structure and protect it from degradation yielding lignin with high C—O linkage content are included.<br/
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