检索结果-南通市图书馆

Endo-microscopy beyond the Abbe and Nyquist limits

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

Light(Science & Applications) 2020年第1期9卷 1246-1257页

作者： Lyubov v.Amitonova Johannes f.de Boer LaserLaB Department of Physics and AstronomyVrije Universiteit AmsterdamDe Boelelaan 10811081 HV AmsterdamThe Netherlands Advanced research Center for Nanolithography(ArCNL) Science Park 1061098 XG AmsterdamThe Netherlands

for several centuries,far-field optical microscopy has remained a key instrument in many scientific disciplines,including physical,chemical,and biomedical ***,far-field imaging has many limitations:the spatial resolution is controlled by the diffraction of light,and the imaging speed follows the Nyquist–Shannon sampling *** recent development of super-resolution techniques has pushed the limits of spatial ***,these methods typically require complicated setups and long acquisition times and are still not applicable to deeptissue ***,we report imaging through an ultra-thin fibre probe with a spatial resolution beyond the Abbe limit and a temporal resolution beyond the Nyquist limit simultaneously in a simple and compact *** use the random nature of mode coupling in a multimode fibre,the sparsity constraint and compressive sensing *** new approach of super-resolution endo-microscopy does not use any specific properties of the fluorescent label,such as depletion or stochastic activation of the molecular fluorescent state,and therefore can be used for label-free *** demonstrate a spatial resolution more than 2 times better than the diffraction limit and an imaging speed 20 times faster than the Nyquist *** proposed approach can significantly expand the realm of the application of nanoscopy for bioimaging.

关键词： beyond limit fibre

On three-dimensional stress analysis of periodic notched plates under tension

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

Science China(Physics,Mechanics & Astronomy) 2014年第9期57卷 1751-1757页

作者： AfSHAr r BErTO f University of Padova Department of Management and Engineering

By using the finite element method,three-dimensional models of a number of periodic blunt and sharp notches subjected to tension loading are *** aim of this research is to investigate the thickness effect on the location of maximum stress and notch stress intensity factor(NSIf)of corresponding blunt and sharp periodic notches *** this aim,different number of periodic notches as well as different notch opening angles are *** for two-dimensional plates weakened by periodic notches some results are available in the literature,this paper first faces the problem of three-dimensional cases.A total of about 100 geometrical configurations are *** is found that,the effect of plate thickness of periodic notched components can be characterized by the relative value with respect to the depth of the notch(H/t).for the blunt periodic notches with relatively higher values of H/t ratio,the value of the maximum tensile stress is located near the free *** the contrary for lower values of H/t,it is placed at the middle *** same behaviour is observed for sharp periodic notches in terms of notch stress intensity factors.

关键词： periodic notches three-dimensional problems notch stress intensity factor stress concentration factor

Ecological niche modeling of the main forest-forming species in the Caucasus

在线全文

学校读者我要写书评

暂无评论

forest Ecosystems 2022年第2期9卷 200-212页

作者： r.Pshegusov f.Tembotova v.Chadaeva Y.Sablirova M.Mollaeva A.Akhomgotov Tembotov Institute of Ecology of Mountain Territories of russian Academy of Science 37a I.Armand StreetNalchik360051Russia

Background:Ecological niche modeling of the main forest-forming species within the same geographic range contributes significantly to understanding the coexistence of species and the regularities of formation of their current spatial *** main abiotic and biotic environmental variables,as well as species dispersal capability,affecting the spatial distribution of the main forest-forming species in the Caucasus,have not been sufficiently ***:We conducted studies within the physiographic boundaries of the Caucasus,including the russian federation,Georgia,Armenia,and *** studies focused on ecological niche modeling of pure fir,spruce,pine,beech,hornbeam,and birch forests through species distribution modeling and the concept of BAM(Biotic-Abiotic-Movement)*** selected 648 geographic records of pure forests *** and SoilGrids databases,statistical tools in r,Maxent were used to assess the influence of abiotic,biotic,and movement factors on the spatial distribution of the forest-forming ***:Geographic expression of fundamental ecological niches of the main forest-forming species depended mainly on topographic conditions and water *** influence reduced the potential ranges of the studied species by 1.2–1.7 times to the geographic expression of their realized niches and led to differences in the distribution of species with similar requirements for abiotic *** factor significantly limited the areas suitable for pure forests(by 1.2–1.8 times compared with geographic expression of realized ecological niches),except for birch ***:Distribution maps,constructed by abiotic,biotic,and movement factors,were the models of the occupied distributional area of the forest-forming species in the *** and movement factors should be considered in modeling studies of forest ecosystems if models are to have biological meaning and reality.

关键词： Distribution modeling Pure forests BAM diagram Maxent Environmental predictor

Protozoan colonization on artificial substrates in relation to water quality in a tropical Indian harbour

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2001年第2期13卷 143-147页

作者： v.r.Bharati r.N.Khan C.Kalavati A.v.raman Department of Zoology Andhra UniversityVisakhapatnam 530003India.

A field study was conducted to evaluate the protozoan colonization patterns on artificial substrates in relation to organic pollution within a tropical harbour. The composition of protozoans and their succession rates on artificial substrates(polyurethane foam units) were compared between two field stations(A and B), and their presence were considered with regards to the prevailing water quality conditions at the study sites. Altogether 44 genera of flagellates and ciliates were documented. The common genera of flagellates encountered included Monas, Polytoma, and Chromalina. Among the ciliates, the predominant genera were Tetrahymena, vorticella, Lagynophyra, and Heloiphyra. These groups exhibited characteristic successional patterns in relation to ambient water quality. At Station A, located close to the sewage outfall, the water quality parameters included poor Secchi disc transparency(0.48m), dissolved oxygen of 1.93 mg/ml, salinity of 18 psu, and temperature 31.3 ℃. Here, the nanoflagellates( spumella ) colonized first, followed by microcilliate( Tetrahymena ) and sessile form( vorticella ). Station B, located on the seaward side, was characterized by relatively less stressed environmental conditions with transparency 1.85m and dissolved oxygen value of 6 04 mg/ml. Salinity of 27.27 psu, and mean temperature of 30 ℃ were recorded at “B'. At this station, the nanoflagellate Polytoma was first documented to colonize on the substrates, followed by microcilliate( Lagynophrya ) and suctorid( Heliophyra ). These findings support the use of protozoans as indicator species for evaluating the hazards posed by organic pollution to natural estuarine communities.

关键词： Protozoan colonization on artificial substrates in relation to water quality in a tropical Indian harbour

Solar spectral conversion based on plastic films of lanthanide-doped ionosilicas for photovoltaics:Down-shifting layers and luminescent solar concentrators

在线全文

学校读者我要写书评

暂无评论

Journal of rare Earths 2020年第5期38卷 531-538页

作者： M.A.Cardoso S.f.H.Correia A.r.frias H.M.r.Goncalves r.f.P.Pereira S.C.Nunes M.Armand P.S.André v.de Zea Bermudez r.A.S.ferreira Department of Physics and CICECO-Aveiro Institute of Materials University of Aveiro3810-193AveiroPortugal Department of Chemistry and CQ-vr University of Tras-os-Montes e Alto Douro5000-801Vila RealPortugal Instituto de Telecomunicacoes University of Aveiro3810-193AveiroPortugal rEQUIMTE Instituto Superior de Engenharia do Porto4200-072PortoPortugal Chemistry Centre and Chemistry Department University of Minho4710-057BragaPortugal CICS-Health Sciences research Center and Chemistry Department University of Beira Interior6201-001CovilhaPortugal Electrical Energy Storage Department CIC EnergiguneParque Tecnologico de AlavaMinano01510Spain Department of Electrical and Computer Engineering Instituto de TelecomunicacoesInstituto Superior TecnicoUniversidade de Lisboa1049-001LisbonPortugal

The mismatch between the photovoltaic(Pv)cells absorption and the solar irradiance on earth is one of the major limitations towards more efficient Pv energy *** aspect was addressed by downshifting the solar irradiance on Earth through luminescent down-shifting layers based on lanthanidedoped surface-functionalized ionosilicas(ISs)embedded in poly(methyl methacrylate)(PMMA)coated on the surface of commercial Si-based Pv *** IS-PMMA hybrid materials exhibit efficient solar radiation harvesting(spectral overlap of^9.5×10^19 photons/(s·m2))and conversion(quantum yield^52%).The direct solar radiation and the down-shifted radiation are partially guided and lost through total internal reflection to the layer edges being unavailable for Pv conversion of the coated Pv *** tuning the down-shifting layer thickness,it also acts as luminescent solar concentrator enabling the collection of the guided radiation by flexible Pv cells applied on the borders of the down-shifting layer leading to an enhancement of the Pv energy conversion from^5%(in the case of the single-use of the luminescent down-shifting layer)to^13%comparing with the bare Pv *** overall electrical output of the device resulted in an absolute external quantum efficiency increase of^32%for the optimized Eu^3+-based films in the Uv spectral region(compared with the bare Pv device,which is among the best values reported so far).

关键词： Ionosilicas Lanthanides Photovoltaics Luminescent solar concentrators Down-shifting layers Silicon photovoltaic cells

Experimental and numerical characterization of 3D‑printed scaffolds under monotonic compression with the aid of micro‑CT volume reconstruction

在线全文

学校读者我要写书评

暂无评论

Bio-Design and Manufacturing 2021年第2期4卷 222-242页

作者： r.Baptista M.f.C.Pereira A.Maurício D.rechena v.Infante M.Guedes CDP2T Departamento de Engenharia MecanicaEscola Superior de Tecnologia de SetúbalInstituto Politécnico de Setúbal2910‑761 SetúbalPortugal CErENA DECivilInstituto Superior TécnicoUniversidade de LisboaAv.Rovisco Pais11049‑001 LisbonPortugal IDMEC Instituto Superior TécnicoUniversidade de LisboaAv.Rovisco Pais11049‑001 LisbonPortugal IPfN Instituto Superior TécnicoUniversidade de Lisboa1049‑001 LisbonPortugal CefEMA Instituto Superior TécnicoUniversidade de LisboaAv.Rovisco Pais11049‑001 LisbonPortugal

Even when damaged by injury or disease bone tissue has the remarkable ability to *** this process is limited by large size bone defects,tissue engineering is responsible for restoring,maintaining or improving tissue *** are support structures,designed to be implanted in the damaged site,supporting mechanical loads and protecting the regenerating bone *** this paper,3D-printed PLA scaffolds with three different porosity values and two different geometries were experimentally and numerically ***-CT analysis showed that fused filament fabrication can be used to produce scaffolds with the desired porosity and 100%of interconnected *** monotonical compression,scaffolds apparent compressive modulus increased from 89 to 918 MPa,while yield stress increased from 2.9 to 27.5 MPa as porosity decreased from 70 to 30%.Open porosity decreased up to 8%on aligned scaffolds and 14%on staggered scaffolds,after compression,while scaffold’s surface-to-volume ratio highest reduction(7.48 to 4.55 mm−1)was obtained with aligned low porosity ***-CT volume reconstruction allowed for scaffold simplified numerical models to be built and *** agreement was found when predicting scaffold’s apparent compressive ***,it can be concluded that 3D printing is a viable scaffold manufacturing technique for trabecular bone replacement.

关键词： Scaffold Pore design Mechanical behavior Micro-CT analysis finite element method

Cerium extraction by metallothermic reduction using cerium oxide powder injection

在线全文

学校读者我要写书评

暂无评论

Journal of rare Earths 2011年第1期29卷 74-76页

作者： J.S.Luna A A.flores v r.Muiz v A.f.fuentes J.Torres N.rodríguez r J.C.Ortiz P.Orozco CINvESTAv Unidad Saltillo Saltillo-Monterrey Highway Km.13.5P.O.Box 66325000SaltilloCoahuilaMéxico faculty of Engineering Autonomous Univer-sity of CoahuilaCamporedondo UnitSaltilloCoahuilaMéxico Department of Metal Mechanics Technological Institute of SaltilloV.Carranza Blvd 2400SaltilloCoahuilaZC 25280México Academic Unit of Engineering Autonomous University of CoahuilaLopez Velarde Av.ZacatecasZac.ZC 98060

This work presented the feasibility of cerium recovery by Al-Mg alloy through the metallothermic reduction of CeO2 to obtain a master alloy Al-4%Ce. The master alloy obtained in this investigation was for the grain refinement and modification of Al-Si alloys. The reagent was incorporated into a molten alloy using the submerged powder injection technique, and metallic samples were obtained during injection. Chemical and microstructural analyses （by inductively coupled plasma （ICP） and scanning electron microscopy （SEM）, respectively） confirmed the possibility of Ce uptake in the bath （0 to 4 wt.%）, as CeO2 was reduced through metallothermic reactions in the molten alloys. Based on the characterization of reaction products, the sequence of the reaction was proposed.

关键词： cerium recovery metallothermic reduction reaction products rare earths

Modelling ballistic impact on military helmets:The relevance of projectile plasticity

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2021年第5期17卷 1699-1711页

作者： A.Caçoilo r.Mourao f.Teixeira-Dias A.Azevedo f.Coghe r.A.f.valente School of Engineering The University of EdinburghEdinburghEH93FGUK Dept.Weapon Systems and Ballistics Royal Military AcademyBrusselsBelgium Centre for Mechanical Technology and Automation Department of Mechanical EngineeringUniversity of AveiroPortugal

The need to develop armour systems to protect against attacks from various sources is increasingly a matter of personal,social and national *** develop innovative armour systems it is necessary to monitor developments being made on the type,technology and performance of the threats(weapons,projectiles,explosives,etc.) Specifically,the use of high protection level helmets on the battlefield is *** development of evaluation methods that can predict injuries and trauma is therefore of major ***,the risk of injuries or trauma that can arise from induced accelerations is an additional *** develop new materials and layouts for helmets it is necessary to study the effects caused by ballistic impacts in the human head on various *** use of numerical simulation is a fundamental tool in this *** work here presented focuses on the use of numerical simulation(finite elements analysis) to predict the consequences of bullet impacts on military helmets on human *** main objectives are to assess the level and probability of head trauma using the Head Injury Criterion,caused by the impact of a 9 mm NATO projectile on a PASGT helmet and to quantify the relevance of projectile plasticity on the whole modelling *** accelerations derived from the impact phenomenon and the deformations caused on the helmet are evaluated using fully three-dimensional models of the helmet,head,neck and *** studies are done at impact angles ranging from 0 to 75°.results are presented and discussed in terms of HIC and probability of acceleration induced trauma *** comparison analyses are done using a rigid and a deformable projectile and it is observed that plastic deformation of the projectile is a significant energy dissipation mechanism in the whole impact process.

关键词： Ballistic impact Helmet impact Plasticity finite element analysis Injury Trauma HIC

Numerical Modelling of the Aeroelastic Behaviour and variable Loads for the Turbine Stage in 3D Transonic flow

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2005年第3期14卷 236-241页

作者： v.I. GNESIN L.v. KOLODYAZHNAYA r. rZADKOWSKI Department of Aerohydromechanics Institute of Mechanical Engineering Problems National Academy of Sciences of Ukraine 2/10 Pozharsky st. Kharkov 61046 Ukraine ProfessorDepartment of Aerohydromechanics Institute of Mechanical Engineering Problems National Academy of Sciences of Ukraine 2/10 Pozharsky st. Kharkov 61046 UkraineDepartment of Dynamics of Machines Institute of Fluid Flow Machinery Polish Academy of Sciences J. Fiszera st. 14 Gdansk 80 952 Poland

In this study presented the algorithm proposed involves the coupled solution of 3-D unsteady flow through a turbine stage and the dynamics problem for rotor-blade motion by the action of aerodynamic forces, without separating the outer and inner flow fluctuations. The partially integrated method involves the solution of the fluid and structural equations separately, but information is exchanged at each time step, so that solution from one domain is used as a boundary condition for the other domain. 3-D transonic gas flow through the stator and rotor blades in relative motion with periodicity on the whole annulus is described by the unsteady Euler conservation equations, which are integrated using the explicit monotonous finite-volume difference scheme of Godunov-Kolgan. The structural analysis uses the modal approach and a 3-D finite element model of a blade. A calculation has been done for the last stage of the steam turbine, under design and off-design regimes. It is shown that the amplitude-frequency spectrum of blade oscillations contains the high frequency harmonics, corresponding to the rotor moving past one stator blade pitch, and low frequency harmonics caused by blade oscillations and flow nonuniformity downstream from the blade row; moreover, the spectrum involves the harmonics which are not multiples of the rotation frequency.

关键词： turbine stage 3D unsteady flow blade oscillations