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A stable CS-FEM for the static and seismic stability of a single square tunnel in the soil where the shear strength increases linearly with depth

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第4期14卷 1253-1265页

作者： h.C.Nguyen l.Nguyen-Son Department of Civil and Environmental Engineering Imperial College LondonLondonUK Department of Civil Engineering and Industrial Design University of LiverpoolLiverpoolUK Faculty of Civil Engineering Ho Chi Minh City University of Technology(HUTECH)Ho Chi Minh CityViet Nam

A numerical procedure using a stable cell-based smoothed finite element method(CS-FEM)is presented for estimation of stability of a square tunnel in the soil where the shear strength increases linearly with *** kinematically admissible displacement fields are approximated by uniform quadrilateral elements in conjunction with the strain smoothing technique,eliminating volumetric locking issues and the singularity associated with the MohreCoulomb ***,a rich set of simulations was performed to compute the static stability of a square tunnel with different geometries and soil *** presented results are in excellent agreement with the upper and lower bound solutions using the standard finite element method(FEM).The stability charts and tables are given for practical use in the tunnel design,along with a newly proposed formulation for predicting the undrained stability of a single square ***,the seismic stability number was computed using the present numerical *** results reveal that the seismic stability number reduces with an increasing value of the horizontal seismic acceleration(a_(h)),for both cases of the weightless soil and the soil with unit ***,the link between the static and seismic stability numbers is described using corrective factors that represent reductions in the tunnel stability due to seismic *** is shown from the numerical results that the corrective factor becomes larger as the unit weight of soil mass increases;however,the degree of the reduction in seismic stability number tends to reduce for the case of the homogeneous ***,this advanced numerical procedure is straightforward to extend to three-dimensional(3D)limit analysis and is readily applicable for the calculation of the stability of tunnels in highly anisotropic and heterogeneous soils which are often encountered in practice.

关键词： Tunnels Stability limit analysis Cell-based smoothed finite element method (CS-FEM) Second-order cone programming(SOCP)

Axonal regeneration and sprouting as a potential therapeutic target for nervous system disorders

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Neural Regeneration Research 2021年第10期16卷 1901-1910页

作者： Katherine l.Marshall Mohamed h.Farah Department of Neurology at Johns hopkins School of Medicine BaltimoreMDUSA

Nervous system disorders are prevalent health issues that will only continue to increase in frequency as the population ***-back axonopathy is a hallmark of many neurologic diseases and leads to axonal disconnection from their targets,which in turn leads to functional *** the course of many of neurologic diseases,axons can regenerate or sprout in an attempt to reconnect with the target and restore synapse *** amyotrophic lateral sclerosis(AlS),distal motor axons retract from neuromuscular junctions early in the disease-course before significant motor neuron *** is evidence of compensatory motor axon sprouting and reinnervation of neuromuscular junctions in AlS that is usually quickly overtaken by the disease *** drugs that enhance compensatory sprouting and encourage reinnervation may slow symptom progression and retain muscle function for a longer period of time in AlS and in other diseases that exhibit dying-back *** remain many outstanding questions as to the impact of distinct disease-causing mutations on axonal outgrowth and regeneration,especially in regards to motor neurons derived from patient induced pluripotent stem *** microfluidic chambers are powerful tools for studying the distal axons of human induced pluripotent stem cells-derived motor neurons,and have recently been used to demonstrate striking regeneration defects in human motor neurons harboring AlS disease-causing *** the human neuromuscular circuit with human induced pluripotent stem cells-derived motor neurons will be critical for developing drugs that enhance axonal regeneration,sprouting,and reinnervation of neuromuscular *** this review we will discuss compensatory axonal sprouting as a potential therapeutic target for AlS,and the use of compartmentalized microfluidic devices to find drugs that enhance regeneration and axonal sprouting of motor axons.

关键词： amyotrophic lateral sclerosis axonal regeneration dying-back axonopathy in vitro neuromuscular junction iPSC-derived motor neurons microfluidic device motor axon sprouting

Spalling characteristics of high-temperature treated granitic rock at different strain rates

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第4期16卷 1280-1288页

作者： l.F.Fan Q.h.Yang X.l.Du The Key laboratory of Urban Security and Disaster Engineering of Ministry of Education Beijing University of TechnologyBeijing100124China

The dynamic spalling characteristics of rock are important for stability analysis in rock *** paper presented an experimental investigation on the dynamic spalling characteristics of granite with different temperatures and strain rates.A series of dynamic spalling tests with different impact velocities were conducted on thermally treated granite at different *** dynamic spalling strengths of granite with different temperatures and strain rates were determined.A model was proposed to correlate the dynamic spalling strength of granite,high temperature and strain *** results show that the spalling strength of granite decreases with increasing ***,the spalling strength of granite with a higher strain rate is larger than that with a lower strain *** proposed model can describe the relationship among dynamic spalling strength of granite,high temperature and strain rate.

关键词： Dynamic spalling characteristics high temperature Strain rate Dynamic loading Granite

Rapid Growth of TiNi intermetallic compound within undercooled Ti_(50)Ni_(50)alloy under electrostatic levitation condition

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Journal of Materials Science & Technology 2021年第18期77卷 82-89页

作者： P.F.Zou C.h.Zheng l.hu h.P.Wang School of Physical Science and Technology Northwestern Polytechnical University.Xi'an710072China

The undercooling dependence of the solidification mechanism was systematically explored by the electrostatic levitation(ESl)*** the experiments,the maximum undercooling reached up to 406 K(0.26 T_l)and the growth velocity of the primary TiNi phase was in-situ determined at various *** the initial increase of alloy undercooling,the value of growth velocity sluggishly rose followed by a power *** this case,the primary TiNi phase preferentially developed as the equiaxed dendrite,then the remnant liquid participated as Ti_(2)Ni andα-Ti phases on the grain *** the undercooling exceeded the critical value of 350 K,the growth velocity of the primary phase displayed a sharply increase ***,the TEM results demonstrated that the precipitation of the intermetallic Ti_(2)Ni compound was gradually restrained during the rapid solidification and the R-phase existing in the TiNi matrix at large undercooling implied that the martensitic transformation was incomplete.

关键词： Undercooling Ti-Ni alloy Solidification Growth kinetics

Effect of interlayer addition on microstructure and mechanical properties of NiTi/stainless steel joint by electron beam welding

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Journal of Materials Science & Technology 2021年第2期61卷 16-24页

作者： h.Niu h.C.Jiang M.J.Zhao l.J.Rong CAS Key laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of ScienceShenyang110016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei230026China

NiTi/Stainless Steel(SS) sheets have been welded via a vacuum electron beam welding process, with three methods(offsetting electron beam to SS side without interlayer, adding Ni interlayer and adding Fe Ni interlayer), to promote mechanical properties of the Ni Ti/SS joints. The joints with different interlayers are all fractured in the weld zone near the Ni Ti side, which is attributed to the enrichment of intermetallic compounds including Fe2 Ti and Ni3 Ti. The fracture mechanisms of different joints are strongly dependent on the types of interlayers, and the joints without interlayer, adding Ni interlayer and adding Fe Ni interlayer exhibit cleavage fracture, intergranular fracture and mixed fracture composed of cleavage and tearing ridge, respectively. Compared with the brittle laves phase Fe2 Ti, Ni3 Ti phase can exhibit certain plasticity, block the crack propagation and change the direction of crack propagation. The composite structure of Ni3 Ti and Fe2 Ti will be formed when the Fe Ni alloy is taken as the interlayer, which provides the joint excellent mechanical properties, with rupture strength of 343 MPa.

关键词： NiTi Stainless steel Electron beam welding Interlayer Mechanical property

Effect of cold-working on corrosion induced damage in lug joints

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Defence Technology（防务技术） 2024年第6期36卷 175-182页

作者： Ramanath M.N Chikmath l. Murthy h. Department of Aerospace Engineering Indian Institute of Technology-MadrasChennai 600036India Department of Aeronautical Engineering KLS Gogte Institute of TechnologyBelagavi 590008India

lug joints are preferred joineries for transferring heavy loads to parent components in aerospace *** experience corrosion due to environmental conditions,improper surface finishes and rubbing displacement between the pin and *** causes damage of different sizes and shapes near the *** degradation due to corrosion-induced damage is modelled as a through-pit at one of the identified critical locations through stress *** effect of this pit on fatigue crack initiation life is ***-hole is pre-stressed by cold-working and the benefits of inducing plastic wake on the intended performance of the lug joint during the damages due to corrosion are brought out and compared with non-cold-worked *** analysis is performed on this lug joint with *** results obtained highlight the benefits of cold-working and the methodology can be extended to damage growth and analyse the effect of surface treatments for better structural integrity of components of aerospace vehicles.

关键词： lug joint Corrosion Crack initiation Cold-working Structural integrity

Methane Dry Reforming over Alumina Supported Co Catalysts

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Chemical Research in Chinese Universities 2004年第4期20卷 457-461页

作者： Sergio l. González Cortés Malcolm l. h. Green Inorganic Chemistry laboratory University of OxfordInorganic Chemistry Laboratory University of Oxford South Parks Road OX1 3QR UKSouth Parks Road OX1 3QR UK

A series of Co/γ-Al_2O_3 catalysts were prepared with the impregnation method and characterized by means of the BET specific surface area, X-ray diffraction(XRD), thermogravimetric analysis(TGA) and laser Raman spectroscopy. The Co/γ-Al_2O_3 catalysts were activated by using h_2, 20%Ch_4/h_2 or Ch_4, respectively. There was no obvious difference between the activities of the Co/γ-Al_2O_3 catalyst activated by using the different activation methods for methane dry reforming. The catalytic properties of the Co/γ-Al_2O_3 catalysts with different Co loadings were also investigated. The optimized Co loading for the Co/γ-Al_2O_3 catalyst pretreated with 20% Ch_4/h_2 is around 12%(mass fraction).

关键词： Methane dry reforming Alumina supported cobalt catalysts Catalytic deactivation

Influence of austenization temperature on the erosion behavior of austempered ductile irons

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Journal of University of Science and Technology Beijing 2008年第1期15卷 29-33页

作者： l.C. Chang l C. hsui l.h. Chen S.T. lui Department of Mechanical Engineering Technology and Science Institute of Northern Taiwan Taipei 112 China Talpei Department of Materials Science and Engineering Cheng-Kung University Talnan 800 China Taipei

The erosion behavior of austempered ductile irons austenized at different temperatures was studied. The results indicate that the erosion rate well correlates with the mechanical properties. At high impact angles, increasing ductility and mechanical energy density results in decreasing erosion rate, whereas increasing hardness reduces the erosion rate at low impact angles. 2008 University of Science and Technology Beijing. All rights reserved.

关键词： austempered ductile iron erosion mechanical properties austenization

STRUCTURE AND SURFACE STUDIES OF Mg_xZn_(1-x)O FIlMS GROWN BY PUlSED lASER DEPOSITION

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Acta Metallurgica Sinica(English letters) 2005年第3期18卷 237-241页

作者： l.Zhuang K.h.Wong DepartmentofAppliedPhysics TheHongKongPolytechnicUniversityKowloonHongKongChina

The structural and surface properties of high-quality epitaxial cubic MgxZn1-xO films deposited by pulsed laser deposition (PlD) were studied by X-ray diffracti on and atomic force microscopy respectively. For films of about 500nm thick, sca ns over a 30μm × 30μm area revealed a surface roughness Ra of about 100nm. Th is relatively large surface roughness is primarily attributed to the particulate and outgrowth during the PlD process. A good epitaxial growth on laAlO3 (lAO ) (100) substrates, however has been obtained for composition x = 0.9, 0.7 and 0 .5 with the heteroepitaxial relationship of (100)■∥(100)lAO (out-of-plane) and (011)■∥(010)lAO (in-plane). These structural qualities suggest that cubic Mgx Zn1-xO alloys films have good potential in a variety of optoelectronic device ap plications.

关键词： pulsed laser deposition thin film XRD MgxZn1-xO