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Assessment of k–ε models using tetrahedral grids to describe the turbulent flow field of a PBT impeller and validation through the PIV technique

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Chinese Journal of Chemical Engineering 2018年第5期26卷 942-956页

作者： Victor X. Mendoza-Escamilla Alejandro Alonzo-Garcia Helvio R. Mollinedo Israel Gonzalez-Neria J. Antonio Yanez-Varela Sergio A. Martinez-Delgadillo depto. electronica Universidad Autonoma Metropolitana Azcapotzalco Av. San Pablo 180 Azcapotzalco CP 07740 Mexico D.F. Mexico CONACyT-Centro de Ingenierfa y Desarrollo Industrial Av. Piaya Pie de la Cuesta 702 Desarrollo San Pablo 76125 Queretaro Qro. Mexico UPIITA Instituto Politecnico Nacional Av. IPN 2580 G.A. Madero CP 07340 Mexico D.F. Mexico depto. Ciencias Basicas Universidad Autonoma Metropolitana Azcapotzalco Av. San Pablo 180 Azcapotzalco CP 07740 Mexico D.F Mexico

In turbulence modeling, the RNG and Realizable models have important improvements in the turbulent production and dissipation terms in comparison to the Standard. The selection of the appropriate turbulence model has an impact on the convergence and solution in STRs, and they are used in mixing, multiphase modeling or as starting solution of transient models as DES and LES. Although there are several studies with the pitched blade turbine(PBT) impeller, most of them used the Standard model as representative of all k–ε models, using structured hexahedral grids composed of low number of cells, and in some cases under axial symmetry ***, in this work the assessment of the Standard, RNG and Realizable models to describe the turbulent flow field of this impeller, using the Multiple Reference Frame(MRF) and Sliding Mesh(SM) approaches with tetrahedral domains in dense grids, is presented. This kind of cell elements is especially suitable to reproduce complex geometries. Flow velocities and turbulent parameters were verified experimentally by PIV and torque measurements. The three models were capable of predicting fairly the pumping number, the power number based on torque, and velocities. Although the RNG improved the predictions of the turbulent kinetic energy and dissipation rate, the Realizable model presented better performance for both approaches. All models failed in the prediction of the total dissipation rate, and a dependence of its value on the number of cells for the MRF was found.

关键词： Tetrahedral grids PIV Turbulent flow k-ε models Stirred vessel

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Structural Peculiarities and Magnetic Properties of Nanoscale Terbium in Tb/Ti and Tb/Si Multilayers

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Chinese Physics Letters 2006年第1期23卷 196-199页

作者： A. V. Svalov V. O. Vas'kovskiy G. V. Kurlyandskaya J. M. Barandiaran I. Orue N. N. Schegoleva A. N. Sorokin Ural State University Lenin Avenue 51 620083 Ekaterinburg Russia Universidad del Pals Vasco UPV-EHU Facultad de Ciencias Depto Electricidad y ElectrOnica Apdo. 644 48080 Bilbao Spain Institute of Metal Physics Ural Branch of RAS Kovalevskaya str. 18 620219 Ekaterinburg Russia

The structure and the magnetic properties of rf-sputtered nauoscale Tb in [Tb/Ti]n and [Tb/Si] multilayers have been studied experimentally. It is found that the structure of Tb layers changes, transforming from a fine-crystalline state of Tb into an amorphous state as the magnetic layer thickness decreases. The observed displacement of a magnetic ordering temperature to the lower temperature range and the shift of magnetic hysteresis obtained in the ZFC-FC terms may be caused by the size effect and the amorphization. Both the first and the second suppress the exchange interaction and decrease the crystalline magnetic anisotropy. The type of material of nonmagnetic spacers between the Tb layers plays a certain role in these changes.

关键词： FERROMAGNETIC-RESONANCE FILMS TEMPERATURE DEPENDENCE THICKNESS LAYERS

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Electrohydromechanical analysis based on conductivity gradient in microchannel

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Chinese Physics B 2008年第12期17卷 4541-4546页

作者：姜洪源任玉坤敖宏瑞 Antonio Ramos School of Mechatronics Engineering Harbin Institute of Technology Department electronica y Electromagnetismo Universidad de SevillaAvda Reina Mercedes s/n Sevilla 41012 Spain

Fluid manipulation is very important in any lab-on-a-chip system. This paper analyses phenomena which use the alternating current （AC） electric field to deflect and manipulate coflowing streams of two different electrolytes （with conductivity gradient） within a microfluidic channel. The basic theory of the electrohydrodynamics and simulation of the analytical model are used to explain the phenomena. The velocity induced for different voltages and conductivity gradient are computed. The results show that when the AC electrical signal is applied on the electrodes, the fluid with higher conductivity occupies a larger region of the channel and the interface of the two fluids is deflected. It will provide some basic reference for people who want to do more study in the control of different fluids with conductivity gradient in a microfluidic channel.

关键词： electrohydrodynamics conductivity gradient theoretical analysis numerical simulation

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Force criterion of different electrolytes in microchannel

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Chinese Physics B 2009年第10期18卷 4349-4352页

作者：任玉坤闫辉姜洪源顾建忠 Antonio Ramos School of Mechatronics Engineering Harbin Institute of Technology Department electronica y Electromagnetismo Universidad de Sevilla Avda Reina Mercedes s/n Sevilla 41012 Spain

The control and handling of fluids is central to many applications of the lab-on-chip. This paper analyzes the basic theory of manipulating different electrolytes and finds the two-dimensional model. Coulomb force and dielectric force belonging to the body force of different electrolytes in the microchannel were analyzed. The force criterion at the interface was concluded, and testified by the specific example. Three basic equations were analyzed and applied to simulate the phenomenon. The force criterion was proved to be correct based on the simulation results.

关键词： force criterion basic theory specific example numerical simulation

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Transfer of Machined Patterns on an Aluminum Plate to Pyrex Glass Using Reactive Ion Etching SF_(6) Plasma without Masks

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Journal of Surface Engineered Materials and Advanced Technology 2014年第5期4卷 262-269页

作者： Carlos M.Ortiz-Lima Fernando J.Quinones-Novelo Alberto Jaramillo-Nunez Jorge Castro-Ramos Insitituto Nacional de Astrofisica Optica y ElectronicaPueblaMexico

A method for etching the surface of a Pyrex glass substrate using the Reactive Ion Etching process without the use of masks is reported. Variations in the machined surface on an auxiliary plate, manufactured in aluminum and placed below a Pyrex glass slide, were transferred to the upper surface of the substrate. SF6 as etching gas and low pressure chamber to promote the increase of mean free path of ions were used. Two etching ratios were found, general, that affects the entire surface of the substrate, and differential, which generates the relief on the surface of the glass. Differential etching depth showed a linear behavior with respect to time;the mean differential etching rate obtained was 43 nm/min. The same phase between the auxiliary plate machining and the etched pattern on the substrate is preserved. With this technique it was possible to manufacture convex and concave surfaces;some examples are given. The arithmetic mean roughness achieved with the proposed method was found to be N1 class, ideal for the development of optical corrector plates.

关键词： Reactive Ion Etching No Masking RIE SF_(6) Plasma Etching

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Accretion/jet activity and narrow [O III] kinematics in young radio galaxies

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Science China(Physics,Mechanics & Astronomy) 2010年第S1期53卷 235-239页

作者： Andrew HUMPHREY Korean Astronomy and Space Science Institute Daejeon 305348 Korea Instituto Nacional de Astrofisica Optica y Electronica(INAOE)Aptdo.Postal 51 y 21672000 PueblaPue.Mexico

We estimate black hole masses and Edenton ratios for a sample of 81 young radio galaxies,which includes 42 compact steep-spectrum(CSS) and 39 gigahertz-peaked spectrum(GPS) *** find that the average black hole(BH) mass of these young radio galaxies is〈log Mbh〉-8.3,which is less than that of radio loud QSOs and low redshift radio galaxies(〈 log Mbh〉-9.0).The CSS/GPS sources have relatively high Eddington ratios,with an average value of〈log Lbol/LEdd〉=-0.75,which are similar to those of narrow line Seyfert 1 galaxies(NLS1s).This suggests that young radio galaxies may not only be in the early stages of their radio activity,but also in the early stage of their accretion *** find that the young radio galaxies,as a class,systematically deviate from the Mbh-σ relation defined by nearby inactive galaxies,when using σ[O III] as a surrogate for stellar velocity dispersion σ.We also find that the deviation of the [O III] line width,Δσ =σ[O III]-σ[pred],is correlated with the Eddington ratio;sources with Lbol/LEdd-1 have the largest deviations,which are similar to those of radio quiet QSOs/NLS1s(i.e.,sources in which the radio jets are absent or weak),and where σ[pred] is calculated from the Tremaine et *** using our estimated BH masses.A similar result has been obtained for 9 linear radio Seyfert *** the basis of these results,we suggest that,in addition to the possible jet-gas interactions,accretion activities may also play an important role in shaping the kinematics of the narrow [O III] line in young radio galaxies.

关键词： accretion accretion discs-ISM:jets and outflows-radio continuum:galaxies-quasars:emission lines

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Analysis and parameter extraction of memristive structures based on Strukov's non-linear model

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Journal of Semiconductors 2018年第12期39卷 106-113页

作者： A.Avila Garcia L.Ortega Reyes Centro de Investigacion y de Estudios Avanzados del Instituto Polit6cnico Nacional Departamento de Ingenieria ElectricaSeccion de Electronica del Estado SolidoMexico 07360Mexico

Diverse models have been proposed for explaining the electrical performance of memristive devices. In principle, the behavior of internal variables associated to each one could be extracted from experimental results. In a former work, thermally grown TiOmemristive structures were built and characterized to obtain the constitutive relationship(magnetic flux versus charge). The aim of this work is to continue that analysis by determining the microscopic parameters within the frame of a simple model. We use the already obtained memristance dependence of time and the basic expressions from the non-linear model proposed by Strukov et al. to compute the state-variable,the mobility of the doping species, the speed of the boundary between the doped and the undoped regions, the voltages and the electric fields on the distinct regions. The power dissipation and its time evolution are also presented. Moreover, a quite different window function from those formerly proposed, which was estimated from experimental data, is also determined. This information provides a straightforward picture of the ionic transport during one cycle of a square voltage waveform within the framework of this simple model. Finally, a quality factor is proposed as the key parameter for actual memristors viewed under the same model.

关键词： memristors parameter extraction non-linear model experimental window function

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Time-expanded phase-sensitive optical time-domain reflectometry

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Light(Science & Applications) 2021年第3期10卷 443-454页

作者： Miguel Soriano-Amat Hugo F.Martins Vicente Duran Luis Costa Sonia Martin-Lopez Miguel Gonzalez-Herraez Maria R.Fernandez-Ruiz Departamento de electronica Universidad de AlcalaEscuela Politecnica Superior28805 MadridSpain Instituto deóptica"Daza de Valdes" IO-CSICC/Serrano 12128006 MadridSpain GROC-UJI Institute of New Imaging TechnologiesUniversity Jaume112071 CastellonSpain

Phase-sensitive optical time-domain reflectometry(CDOTDR)is a well-established technique that provides spatiotemporal measurements of an environmental variable in real *** unique capability is being leveraged in an everincreasing number of applications,from energy transportation or civil security to *** date,a wide number of different approaches have been implemented,providing a plethora of options in terms of performance(resolution,acquisition bandwidth,sensitivity or range).However,to achieve high spatial resolutions,detection bandwidths in the GHz range are typically required,substantially increasing the system cost and ***,we present a novel OOTDR approach that allows a customized time expansion of the received optical ***,the presented technique reaches cm-scale spatial resolutions over t km while requiring a remarkably low detection bandwidth in the MHz *** approach relies on the use of dual-comb spectrometry to interrogate the fibre and sample the backscattered *** phase-spectral coding is applied to the employed combs to maximize the signal-to-noise ratio of the sensing scheme.A comparison of the proposed method with alternative approaches aimed at similar operation features is provided,along with a thorough analysis of the new *** results demonstrate a radically novel high-resolution OOTDR scheme,which could promote new applications in metrology,borehole monitoring or aerospace.

关键词： optical phase expanded

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Fabrication of cost-effective, highly reproducible large area arrays of nanotriangular pillars for surface enhanced Raman scattering substrates

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Nano Research 2016年第10期9卷 3075-3083页

作者： Kudilatt Hasna Aldrin Antony Joaquim Puigdollers Kumaran Rajeev Kumar Madambi Kunjukuttan Jayaraj Nanophotonic & Optoelectronic Devices Laboratory Department of Physics Cochin University of Science & Technology Kochi 682 022 India Department of Instrumentation Cochin University of Science & Technology Kochi 682 022 India Department of Energy Science and Engineering Indian Institute of Technology Bombay Maharashtra 400 076 India Department of Enginyeria electronica Universitat Politecnica Catalunya C/Jordi Girona 31 Modul C4 Barcelona 08034 Spain

Development of cost-effective, highly reproducible non-conventional fabrication techniques for anisotropic metal nanostructures is essential to realizing potential applications of plasmonic devices, photonic devices, and surface enhanced Raman scattering （SERS） phenomenon based sensors. This report highlights the fabrication of nanotriangle arrays via nanoimprinting to overcome difficulties in creating large-area SERS active substrates with uniform, reproducible Raman signals. Electron beam lithography of anisotropic nanostructures, formation of arrays of nanotriangles in silicon and the transfer of triangular shapes to polymethylmethacrylate （PMMA） sheets via nanoimprinting have not been reported elsewhere. The reuse of silicon masters offers potential for production of low cost SERS substrates. The SERS activity and reproducibility of nanotriangles are illustrated and a consistent average enhancement factor of up to -2.9 × 1011, which is the highest value reported for a patterned SERS substrate, is achieved.

关键词： metal nanostructures localized surface plasmon resonance (LSPR) surface enhanced Ramanscattering (SERS) substrate enhancement factor

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Interlayer Coupling in Co/Ti/（Gd-Co）/Ti Artificial Layered Ferrimagnet

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Chinese Physics Letters 2005年第12期22卷 3169-3172页

作者： A. V. Svalov A. Fernández V. O. Vas'kovskiy M. Tejedor R. Lopez Anton J. M. Barandiarán G. V. Kurlyandskaya Institute of Physics and Applied Mathematics Ural State University Lenin Avenue 51 620083 Ekaterinburg Russia Departamento de Fisica Universidad de Oviedo Avenida Calvo Sotelo s/n 33007 Oviedo Asturias Spain Departamento de Electricidad y electronica Facultad de Ciencia y Tecnologia Universidad del Pais Vasco UPV/EHU PO Box 644 48080 Bilbao Spain

The magnetic properties and the structure of [Co/Ti/Gd0.36 Co0.64/Ti]4/Co multilayers are investigated by means of torque magnetometer, vibrating sample magnetometer and transverse magneto-optic Kerr effect （TMOKE） measurements and the atomic force microscopy. Due to interlayer exchange interaction, Co and Gd-Co layers form a macroscopic ferrimagnetic system. The change in the sign of the TMOKE hysteresis loops near the compensation temperature and field induced magnetic phase transitions are found. The latter can be characterized by a critical field which shows a linear variation with the temperature. The magnetic properties of these multilayers from many points of view are similar to those of bulk ferrimagnets.

关键词： THIN-FILMS MULTILAYERS

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