检索结果-南通市图书馆

Effect of sample size on the response of DEM samples with a realistic grading

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Particuology 2014年第4期12卷 107-115页

作者： Xin Huang kevin j.Hanley Catherine O'Sullivan Fiona C.Y.Kwok Skempton Building Department of Civil and Environmental EngineeringImperial College LondonLondon SW7 2AZUnited Kingdom Haking Wong Building Department of Civil EngineeringThe University of Hong Kong

This paper shows that for DEM simulations of triaxial tests using samples with a grading that is repre- sentative of a real soil, the sample size significantly influences the observed material response. Four DEM samples with identical initial states were produced： three cylindrical samples bounded by rigid wails and one bounded by a cubical periodic cell, When subjected to triaxial loading, the samples with rigid boundaries were more dilative, stiffer and reached a higher peak stress ratio than the sample enclosed by periodic boundaries. For the rigid-wall samples, dilatancy increased and stiffness decreased with increasing sample size, The periodic sample was effectively homogeneous, The void ratio increased and the contact density decreased close to the rigid walls, This heterogeneity reduced with increasing sample size. The positions of the critical state lines （CSLs） of the overall response in e-log p＇ space were sensitive to the sample size, although no difference was observed between their slopes. The critical states of the interior regions of the rigid-wall-bounded samples approached that of the homogeneous periodic sample with increasing sample size. The ultimate strength of the material at the critical state is independent of sample size.

关键词： Discrete element method Sample size Rigid boundary Periodic boundary Critical state

Expansion properties for finite subdivision rules I Dedicated to the Memories of William P. Thurston and Lei Tan

在线全文

学校读者我要写书评

暂无评论

Science China Mathematics 2018年第12期61卷 2237-2266页

作者： William j.Floyd Walter R.Parry kevin M.Pilgrim Department of Mathematics Virginia Tech Department of Mathematics and Statistics Eastern Michigan University Department of Mathematics Indiana University

Among Thurston maps (orientation-preserving, postcritically finite branched coverings of the 2-sphere to itself), those that arise as subdivision maps of a finite subdivision rule form a special family. For such maps, we investigate relationships between various notions of expansion—combinatorial, dynamical, algebraic,and coarse-geometric.

关键词： finite subdivision rule expanding map postcritically finite Thurston map

Anodic Cyclizations, Seven-Membered Rings, and the Choice of Radical Cation *** Pathways

在线全文

学校读者我要写书评

暂无评论

Chinese journal of Chemistry 2019年第7期37卷 672-678页

作者： Robert j.Perkins Ruozhu Feng Qingquan Lu kevin D.Moeller Department of Chemistry Washington University in St.Louis St.Louis MO 63130 USA

While many steps in an oxidative cyclization reaction can be important,it is the cyclization step itself that plays the central *** this step does not proceed well,then optimization of the rest of the sequence is *** report here that the key to the cyclization is channeling the reaction down the correct *** reactions require the use of a radical pathway and some require the use of a radical cation *** example of each is provided along with a strategy for accessing both pathways using a common intermediate.

关键词： Anodic Cyclizations Seven-Membered Rings

Merits and limitations of TiO2-based photocatalytic pretreatment of soils impacted by crude oil for expediting bioremediation

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Chemical Science and Engineering 2017年第3期11卷 387-394页

作者： Yu Yang Hassan javed Danning Zhang Deyi Li Roopa Kamath kevin McVey Kanwartej Sra Pedro j.j. Alvarez Department of Civil and Environmental Engineering Rice University Houston TX 77005 USA Department of Chemistry Rice University Houston TX 77005 USA Department of Civil and Environmental Engineering Tongji University Shanghai 200092 China Chevron Energy Technology Company Houston TX 77002 USA

Heavy hydrocarbons （HHCs） in soils impacted by crude oil spills are generally recalcitrant to biodegrada- tion due to their low bioavailability and complex chemical structure. In this study, soils were pretreated with varying concentrations of ultraviolet radiation A （UVA） or ultraviolet radiation C （UVC） activated titanium dioxide （TiO2）（1%-5%） under varying moisture conditions （0%- 300% water holding capacity （WHC）） to enhance biodegradation of HCCs and shorten remediation time- frames. We demonstrate that pretreatment of impacted soils with UVC-activated TiO2 in soil slurries could enhance bioremediation of HHCs. Total petroleum hydrocarbon （TPH） removal after 24 h exposure to UVC （254 nm and 4.8 mW/cm2） was （19.15：1.6）% in slurries with 300% WHC and 5 wt-% TiO2. TPH removal was non-selective in the C15-C36 range and increased with moisture content and TiO2 concentration. In a 10-d bioremediation test, TPH removal in treated soil increased to （26.05：0.9）%, compared to （15.45：0.8）% for controls without photo- catalytic pre-treatment. Enhanced biodegradation was also confirmed by respirometry. This suggests that addition of UVC-activated TiO2 to soil slurries can transform recalcitrant hydrocarbons into more bioavailable and biodegradable byproducts and increase the rate of subsequent biodegradation. However, similar results were not observed for soils pretreated with UVA activated TiO2. This suggests that activation of TiO2 by sunlight and direct addition of TiO2 to unsaturated soils within landfarming setting may not be a feasible approach. Nevertheless, less than 1% of UVA （7.5 mW/cm2） or UVC （1.4 mW/cm2） penetrated beyond 0.3 cm soil depth, indicating that limited light penetration through soil would hinder the ability of TiO2 to enhance soil bioremediation under land farming conditions.

关键词： ZiO2 pretreatment bioremediation total petroleum hydrocarbons ultraviolet

Liquid-phase 3D bioprinting of gelatin alginate hydrogels:influence of printing parameters on hydrogel line width and layer height

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Bio-Design and Manufacturing 2019年第3期2卷 172-180页

作者： Maha Alruwaili jose A.Lopez kevin McCarthy Emmanuel G.Reynaud Brian j.Rodriguez Conway Institute of Biomolecular and Biomedical Research University College DublinDublinIreland School of Physics University College DublinDublinIreland School of Biomolecular and Biomedical Science University College DublinDublinIreland

Extrusion-based 3D bioprinting is a direct deposition approach used to create three-dimensional(3D)tissue scaffolds typically comprising *** are hydrated polymer networks that are chemically or physically ***,3D bioprinting is performed in air,despite the hydrated nature of hydrogels and the potential advantage of using a liquid phase to provide cross-linking and otherwise functionalize the *** this work,we print gelatin alginate hydrogels directly into a cross-linking solution of calcium chloride and investigate the influence of nozzle diameter,distance between nozzle and surface,calcium chloride concentration,and extrusion rate on the dimensions of the printed *** hydrogel layer height was generally found to increase with increasing extrusion rate and nozzle distance,according to the increased volume extruded and the available space,*** addition,the hydrogel width was generally found to increase with decreasing nozzle distance and cross-linking concentration corresponding to confinement-induced spreading and low crosslinking regimes,***/height ratios of^1 were generally achieved when the nozzle diameter and distance were comparable above a certain cross-linking *** these relationships,biocompatible 3D multilayer structures were successfully printed directly into calcium chloride cross-linking solution.

关键词： Gelatin alginate Hydrogel Additive manufacturing 3D printing 3D bioprinting Biomaterials Extrusion Bioplotting

A Comprehensive Overview of Skeletal Phenotypes Associated with Alterations in Wnt/β-catenin Signaling in Humans and Mice

在线全文

学校读者我要写书评

暂无评论

Bone Research 2013年第1期1卷 27-71页

作者： kevin A.Maupin Casey j.Droscha Bart O.Williams Program for Skeletal Pathobiology and Center for Tumor Metastasis Van Andel Research Institute333 Bostwick NEGrand RapidsMI 49503USA

The Wnt signaling pathway plays key roles in differentiation and development and alterations in this signaling pathway are causally associated with numerous human diseases. While several laboratories were examining roles for Wnt signaling in skeletal development during the 1990s, interest in the pathway rose exponentially when three key papers were published in 2001-2002. One report found that loss of the Wnt co-receptor, Low-density lipoprotein related protein-5 （LRPS）, was the underlying genetic cause of the syndrome Osteoporosis pseudoglioma （OPPG）. OPPG is characterized by early-onset osteoporosis causing increased susceptibility to debilitating fractures. Shortly thereafter, two groups reported that individuals carrying a specific point mutation in LRP5 （G171V） develop high-bone mass. Subsequent to this, the causative mechanisms for these observations heightened the need to understand the mechanisms by which Wnt signaling controlled bone development and homeostasis and encouraged significant investment from biotechnology and pharmaceutical companies to develop methods to activate Wnt signaling to increase bone mass to treat osteoporosis and other bone disease. In this review, we will briefly summarize the cellular mechanisms underlying Wnt signaling and discuss the observations related to OPPG and the high-bone mass disorders that heightened the appreciation of the role of Wnt signaling in normal bone development and homeostasis. We will then present a comprehensive overview of the core components of the pathway with an emphasis on the phenotypes associated with mice carrying genetically engineered mutations in these genes and clinical observations that further link alterations in the pathway to changes in human bone.

关键词： Wnt signaling mouse models Lrp5/Lrp6 -catenin skeletal phenotypes

Friction characteristics of confined inflatable structures

在线全文

学校读者我要写书评

暂无评论

Friction 2014年第4期2卷 365-390页

作者： Eduardo M.SOSA Gregory j.THOMPSON Ever j.BARBERO Subhadeep GHOSH kevin L.PEIL Department of Civil and Environmental Engineering West Virginia UniversityMorgantownWV 26506-6103USA Department of Mechanical and Aerospace Engineering West Virginia UniversityMorgantownWV 26506-6106USA

The availability of high‐strength fabrics and progress in the development of large‐scale inflatable technology made possible the creation of temporary and quickly deployable structures for protection of underground *** structures are relatively lightweight and portable,and can maintain the required rigidity while in *** benefits have prompted the development of inflatable structures for use in confined spaces,such as tunnels and large‐diameter pipes to act as barriers for containing flooding with minimal infrastructure *** work presents experimental results obtained from the evaluation of frictional characteristics of the fabric material that constitute the structural membrane of confined inflatable structures developed for protection of underground transportation tunnels and other large *** tests at coupon level and slippage tests in a reduced‐scale inflatable structure were performed in order to evaluate the frictional characteristics of Vectran *** at coupon level were performed to determine the friction coefficient for different surface types and *** with the reduced‐scale inflatable structure contributed to the understanding of the friction characteristics at system level when subjected to different pressurization or depressurization sequences designed to induce *** results indicate that friction coefficient values at coupon level are about 29 percent higher than values derived from reduced‐scale tests.

关键词： friction fabric materials inflatable structures slippage Vectran

Frontier orbitals and quasiparticle energy levels in ionic liquids

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

npj Computational Materials 2020年第1期6卷 441-447页

作者： juhan Matthias Kahk Ivar Kuusik Vambola Kisand kevin R.j.Lovelock johannes Lischner Department of Materials Imperial College LondonSouth KensingtonLondon SW72AZUK Institute of Physics University of TartuW.Ostwaldi 150411 TartuEstonia School of Chemistry Food and PharmacyUniversity of ReadingReading RG66DXUK Department of Physics and Department of Materials and the Thomas Young Centre for Theory and Simulation of Materials Imperial College LondonLondon SW72AZUK

Ionic liquids play an important role in many technological applications and a detailed understanding of their frontier molecular orbitals is required to optimize interfacial barriers,reactivity and stability with respect to electron injection and *** this work,we calculate quasiparticle energy levels of ionic liquids using first-principles many-body perturbation theory within the GW approximation and compare our results to various mean-field approaches,including semilocal and hybrid density-functional theory and *** find that the mean-field results depend qualitatively and quantitatively on the treatment of exchange-correlation effects,while GW calculations produce results that are in excellent agreement with experimental photoelectron spectra of gas phase ion pairs and ionic *** results establish the GW approach as a valuable tool for understanding the electronic structures of ionic liquids.

关键词： liquids ionic quasi

The parallel-plate resonator:An RF probe for MR and MRI studies over a wide frequency range

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Magnetic Resonance Letters 2023年第4期3卷 306-318页

作者： Andres Ramírez Aguilera kevin j.Sanders Gillian R.Goward Bruce *** UNB MRI Centre Department of PhysicsUniversity of New BrunswickFrederictonNew BrunswickE3B 5A3Canada Department of Chemistry McMaster UniversityHamiltonOntarioL8S 4L8Canada

We explore the use of the parallel-plate resonator for the study of thin cuboid samples over a wide range of magnetic resonance *** parallel-plate resonator functions at frequencies from tens to hundreds of *** parallel-plate resonators are presented and discussed in a frequency range from 8 to 500 *** resonance experiments were performed on both horizontal and vertical bore magnet systems with lithium and hydrogen ***-plate radiofrequency(RF)probes are easy to build and easy to *** and simulations showed good sensitivity of the parallel-plate RF probe geometry with a small decrease in sensitivity at higher frequencies.

关键词： Parallel-plate resonator Optimization Magnetic resonance/magnetic resonance imaging(MR/MRI) Batteries