检索结果-南通市图书馆

Science China(Physics,Mechanics & Astronomy) 2008年第5期51卷 519-531页

作者： z.j.YANG A.j.DEEKS College of Civil Engineering and Architecture Zhejiang University School of Civil and Resource Engineering University of Western Australia

A frequency-domain approach based on the semi-analytical scaled boundary finite element method(SbFEM) was developed to calculate dynamic stress intensity factors(DSIFs) at bimaterial interface cracks subjected to transient ***-cause the stress solutions of the SbFEM in the frequency domain are analytical in the radial direction,and the complex stress singularity at the bimaterial interface crack tip is explicitly represented in the stress solutions,the mixed-mode DSIFs were calculated directly by *** complex frequency-response functions of DSIFs were then used by the fast Fourier transform(FFT) and the inverse FFT to calculate time histories of DSIFs.A benchmark example was *** re-sults were obtained by modelling the example with a small number of degrees of freedom due to the semi-analytical nature of the SbFEM.

关键词： scaled boundary finite element method bimaterial interface crack frequency domain dynamic stress intensity factors fast Fourier transform

Cu-assisted austenite reversion and enhanced TRIP effect in maraging stainless steels

在线全文

学校读者我要写书评

暂无评论

journal of Materials Science & Technology 2022年第9期104卷 52-58页

作者： M.C.Niu K.Yang j.H.Luan W.Wang z.b.j.ao School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China Shi-changxu Innovation Center for Advance Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Department of Mechanical Engineering The Hong Kong Polytechnic UniversityHong KongChina Department of Materials Science and Engineering City University of Hong KongHong KongChina The Hong Kong Polytechnic University Shenzhen Research Institute ShenzhenGuangdongChina

Control of the formation and stability of reverted austenite is critical in achieving a favorable combination of strength,ductility,and toughness in high-strength *** this work,the effects of Cu precipitation on the austenite reversion and mechanical properties of maraging stainless steels were investigated by atom probe tomography,transmission electron microscopy,and mechanical *** results indicate that Cu accelerates the austenite reversion kinetics in two manners:first,Cu,as an austenite stabilizer,increases the equilibrium austenite fraction and hence enhances the chemical driving force for the austenite formation,and second,Cu-rich nanoprecipitates promote the austenite reversion by serving as heterogeneous nucleation sites and providing Ni-enriched chemical conditions through interfacial *** addition,the Cu precipitation hardening compensates the strength drop induced by the formation of soft reverted *** tensile deformation,the metastable reverted austenite transforms to martensite,which substantially improves the ductility and toughness through a transformation-induced plasticity(TRIP)*** Cu-added maraging stainless steel exhibits a superior combination of a yield strength of~1.3 GPa,an elongation of~15%,and an impact toughness of~58 j.

关键词： Maraging stainless steel TRIP effect Austenite reversion Cu-rich nanoprecipitate

Evolution of the Microstructure and Strength in the Nugget zone of Friction Stir Welded SiCp/Al-Cu-Mg Composite

在线全文

学校读者我要写书评

暂无评论

journal of Materials Science & Technology 2014年第1期30卷 54-60页

作者： D.Wang b.L.Xiao Q.z.Wang z.Y.Ma Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences University of Science and Technology of China

A 6 mm-thick SiCp/2009AI composite plate was successfully joined by friction stir welding （FSW） using an ultrahard material tool to investigate the evolution of the microstructure and the strength in the nugget zone （Nz）. While some SiC particles were broken up during FSW, most of them rotated in the matrix. Large compound particles on the interfaces were broken off during FSW, whereas the amorphous layer and small compound particles remained on the interfaces. The dynamically recrystallized AI grains nucleated on the surface of fractured SiC particles during FSW, forming nano-sized grains around the SiC particles. The yield strength of the Nz decreased slightly due to the variation in the size, shape, and distribution of the SiC particles. The clean interfaces were beneficial to the load transfer between SiC particles and AI matrix and then increased the ultimate tensile strength of the Nz.

关键词： Metal-matrix composites Friction stir welding Microstructure Mechanical properties

Numerical investigation on the flowfield of “swallowtail” cavity for supersonic mixing enhancement

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2009年第1期25卷 37-44页

作者： C. Wang z. jiang z. Hu j. Lu Institute or Mechanics. Chinese Academy of Sciences 100190 Beijing China ReCAPT Gyeongsang National University JinjuKyeongnam 660-701 South Korea

A ＂swallowtail＂ cavity for the supersonic combustor was proposed to serve as an efficient flame holder for scramjets by enhancing the mass exchange between the cavity and the main flow. A numerical study on the ＂swallow- tail＂ cavity was conducted by solving the three-dimensional Reynolds-averaged Navier-Stokes equations implemented with a k-e turbulence model in a multi-block mesh. Turbu- lence model and numerical algorithms were validated first, and then test cases were calculated to investigate into the mechanism of cavity flows. Numerical results demonstrated that the certain mass in the supersonic main flow was sucked into the cavity and moved spirally toward the combustor walls. After that, the flow went out of the cavity at its lateral end, and finally was efficiently mixed with the main flow. The comparison between the ＂swallowtail＂ cavity and the conventional one showed that the mass exchanged between the cavity and the main flow was enhanced by the lateral flow that was induced due to the pressure gradient inside the cavity and was driven by the three-dimensional vortex ring generated from the ＂swallowtail＂ cavity structure.

关键词： Supersonic mixing - Flame holder "Swallowtail" cavity - Combustion ignition Numerical simulation

Synthesis of Single-Crystal TiO_2 Nanowire Using Titanium Monoxide Powder by Thermal Evaporation

在线全文

学校读者我要写书评

暂无评论

journal of Materials Science & Technology 2012年第5期28卷 385-390页

作者： z.G.Shang z.Q.Liu P.j.Shang j.K.Shang Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China

TiO 2 nanowires were synthesized successfully in a large quantity by thermal evaporation using titanium monoxide powder as precursor. X-ray diffraction results showed that all the products were pure rutile phase of TiO 2 . According to microstructural observations, the nanowires have two typical morphologies, a long straight type and a short tortuous type. The straight nanowires were obtained at a wide temperature range of 900–1050 ℃, while the tortuous ones were formed below 900 ℃. Transmission electron microscopy characterization revealed that both the straight and the tortuous nanowires are single-crystal rutile TiO 2 . The preferential growth direction of the nanowires was determined as [110] orientation according to electron diffraction and high-resolution image analyses. The morphological change of TiO 2 nanowires was discussed by considering the different atomic diffusion rates of Ti atoms caused by the phase transformation in Ti substrate at around 900 ℃.

关键词： Rutile-TiO 2 Alloy nanowires Transmission electron microscopy (TEM) characterization Crystal structure identification Growth mechanism Thermal evaporation

Relation Reconstructive binarization of word embeddings

在线全文

学校读者我要写书评

暂无评论

Frontiers of Computer Science 2022年第2期16卷 47-54页

作者： Feiyang PAN Shuokai LI Xiang ao Qing HE Key Lab of Intelligent Information Processing of Chinese Academy of Sciences(CAS) Institute of Computing TechnologyCASBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

Word-embedding acts as one of the backbones of modern natural language processing(NLP).Recently,with the need for deploying NLP models to low-resource devices,there has been a surge of interest to compress word embeddings into hash codes or binary vectors so as to save the storage and memory ***,existing work learns to encode an embedding into a compressed representation from which the original embedding can be *** these methods aim to preserve most information of every individual word,they often fail to retain the relation between words,thus can yield large loss on certain *** this end,this paper presents Relation Reconstructive binarization(R2b)to transform word embeddings into binary codes that can preserve the relation between *** its heart,R2b trains an auto-encoder to generate binary codes that allow reconstructing the wordby-word relations in the original embedding *** showed that our method achieved significant improvements over previous methods on a number of tasks along with a space-saving of up to 98.4%.Specifically,our method reached even better results on word similarity evaluation than the uncompressed pre-trained embeddings,and was significantly better than previous compression methods that do not consider word relations.

关键词： embedding compression variational auto-encoder binary word embedding

Effect of extrusion temperature on microstructure and mechanical properties of a low-alloying and ultra-high strength Mg-zn-Ca-Mn matrix composite containing trace TiC nanoparticles

在线全文

学校读者我要写书评

暂无评论

journal of Magnesium and Alloys 2020年第3期8卷 676-691页

作者： K.b.Nie z.H.zhu K.K.Deng j.G.Han College of Materials Science and Engineering Taiyuan University of TechnologyTaiyuan 030024PR China Sharvci key laboratory of advanced magnesium-based materials Taiyuan University of TechnologyTaiyuan 030024PR China

Mechanical properties of microalloying Mg-2.2zn-1.8Ca-0.5Mn(wt%)matrix composites reinforced by 0.5 wt%TiC nanoparticles before and after extrusion were investigated based on the detailed microstructural analysis.A uniform distribution of TiC nanoparticles was realized in the nanocomposite by the method of ultrasonic-assisted semisolid *** morphology of eutectic Ca2Mg6zn3 phases changed from plate-like in the free TiC nanoparticles region to lamellar in the dense TiC nanoparticles region for the as-cast *** the grain structure and precipitates were obviously refined as the extrusion temperature decreased from 350 to 270℃.The nanocomposite exhibited excellent tensile yield strength(352-428 MPa)which was governed by the extrusion *** grain refinement strengthening with the contribution ratio of^80%to this strength increment was much higher relative to thermal expansion effect,Orowan strengthening and dislocation *** recrystallized grain structure with a substantial of ne precipitates appeared in the nanocomposite extruded at 270℃.The refined grain structure was not only due to dynamic recrystallization,but also the synergistic pinning effect of nano-TiCp,precipitated Mgzn2 and α-Mn *** tensile toughness value of nanocomposite after extrusion improved with increasing the extrusion *** micro-cracks formed along the remnant coarse Ca2Mg6zn3 led to the structural failure during tension.

关键词： Magnesium matrix nanocomposite Microstructure Mechanical properties:Strengthening mechanism Extrusion

Non-alcoholic fatty liver disease: What has changed in the treatment since the beginning?

在线全文

学校读者我要写书评

暂无评论

World journal of Gastroenterology 2014年第39期20卷 14219-14229页

作者： bülent baran Filiz Akyüz Division of Gastroenterohepatology Department of Internal Medicine Istanbul University Istanbul Faculty of Medicine Capa 34093 Istanbul Turkey

Non-alcoholic fatty liver disease(NAFLD) is an umbrella term to describe the entire spectrum of this common liver disease. In patients with NAFLD, especially those with non-alcoholic steatohepatitis(NASH), most often have one or more components of the metabolic syndrome, but this is not universal. Although most patients with NAFLD share many clinical features, only a subset of patients develops significant liver inflammation and progressive fibrosis. On the other hand, not all patients with NASH exhibit insulin resistance. NASH can be seen in patients who are lean and have no identifiable risk factors. Many clinical studies have tried numerous drugs and alternative medicine, however, investigators have failed to identify a safe and effective therapy for patients with NASH. As summarized, the heterogeneity of pathogenic pathways in individual patients with NASH may warrant the development of an individualized treatment according to the underlying pathogenic pathway. The differentiation of pathogenetic targets may require the development of diagnostic and prognostic biomarkers, and the identification of genetic susceptibilities. At present, evidence-based medicine provides only a few options including life-style modifications targeting weight loss, pioglitazone and vitamin E in non-diabetic patients with biopsy-proven NASH.

关键词： Non-alcoholic steatohepatitis Pathogenesis Inflammation Fibrosis Life-style changes Pharmacologic treatment

Small extrachromosomal circular DNA in amyotrophic lateral sclerosis matter

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Neural Regeneration Research 2025年第5期20卷 1411-1413页

作者： Marcos j.Arauzo-bravo Daniela Gerovska Matthias Schwab Alexandra Kretz Computational biology and Systems biomedicine Biodonostia Health Research InstituteSan SebastianSpain basque Foundation for Science IKERBASQUEBilbaoSpainMax Planck Institute for Molecular BiomedicineComputational Biology and Bioinformatics GroupMünsterNorth Rhine-WestphaliaGermany Department of Cell biology and Histology Faculty of Medicine and NursingUniversity of Basque Country(UPV/EHU)LeioaSpain Department of Neurology Jena University HospitalJenaThuringiaGermany

Comprehensive studies identify motor neuron spectrum disorders including amyotrophic lateral sclerosis(ALS)as globally rising fatal disorders with the highest prevalence in aging populations,influenced by ethnicity and ancestry(GbD 2016 Motor Neuron Disease Colla borators,2018).While~10% of diagnoses involve a family history(fALS),most cases are considered sporadic(sALS).However,population-based studies suggest that even cases without a common index mutation impart heritability(Ryan et al.,2019),indicating a crucial role of rare and as yet unknown genetic denominators.

关键词： amyotrophic sclerosis

A Parallel boundary Element Formulation for Tracking Multiple Particle Trajectories in Stoke’s Flow for Microfluidic Applications

在线全文

学校读者我要写书评

暂无评论

Computer Modeling in Engineering & Sciences 2015年第3期104卷 227-249页

作者： z.Karakaya b.baranoglu b.Çetin A.Yazici Computer Engng.Dept. Atilim UniversityTurkey Manufacturing Engng.Dept. Atilim UniversityTurkey Microfluidics & Lab-on-a-chip Research Group Mech.Engng.Dept.Bilkent UniversityTurkey Software Engng.Dept. Atilim UniversityTurkey

A new formulation for tracking multiple particles in slow viscous flow for microfluidic applications is *** method employs the manipulation of the boundary element matrices so that finally a system of equations is obtained relating the rigid body velocities of the particle to the forces applied on the *** formulation is specially designed for particle trajectory tracking and involves successive matrix multiplications for which SMP(Symmetric multiprocessing)parallelisation is *** is observed that present formulation offers an efficient numerical model to be used for particle tracking and can easily be extended for multiphysics simulations in which several physics involved.

关键词： boundary Element Method particle tracking Stoke's flow parallel computing