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Parametric optimisation of two Pelton turbine runner designs using CFD

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Journal of Hydrodynamics 2015年第3期27卷 403-412页

作者： IDoNIS Audrius PANAGIoToPoULoS Alexandros AGGIDIS George A. ANAGNoSToPoULoS John S. PAPANToNIS Dimitris e. Lancaster University Renewable energy Group and Fluid Machinery Group engineering Department Lancaster University School of Mechanical engineering National Technical University of Athens

This paper aims to develop a generic optimisation method for Pelton turbine runners using computational fluid dynamics （CFD）. Two different initial runners are optimised to achieve more generic results. A simple bucket geometry based on existing bibliography is parameterised and initially optimised using fast Lagrangian solver （FLS）. It is then further optimised with a more accurate method using ANSYS Fluent. The second geometry is a current commercial geometry with good initial performance and is optimised using ANSYS CFX. The analytical results provided by CFX and Fluent simulations are used to analyse the characteristics of the flow for different runner geometries.

关键词： hydropower Pelton impulse turbines numerical modelling bucket geometry parameterisation optimisation

Influence of bismuth on magnetism and magnetocaloric properties of LaFe_(11.6)Si_(1.4) intermetallic compound

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Journal of Rare earths 2015年第7期33卷 740-745页

作者： A.Boutahar K.Zehani L.Bessais H.Lassri e.K.Hlil LPMMAT Hassan II University-Casablanca Faculty of Science Ain Chock BP 5366 Maarif-Casablanca Morocco ICMPe-CMTR UMR CNRS 7182 2-8 H. Dunant St 94320 Thiais France Néel Institue CNRS and Joseph Fourier University

Crystal structure, magnetic properties and magnetocaloric effects （MCe） of La1-xBixFe1 1.4Si1.6 （x=0.0 and 0.1） compounds were investigated by X-ray diffraction and magnetization measurements. The La1-xBixFe11.4Si1.6 compounds presented a cubic NaZnx3 type structure. First, the magnetization behavior and the magnetic transition were analyzed in terms of Landau theory. Then, Bi substitution for La in La1-xBixFe11.4Si1.6 compounds led to a decrease in magnetic entropy change （-△SM^max） but an increase in Curie temperature （Tc） significantly. The significant increase of Tc by Bi substitution from 202.5 to 256 K for x=0.0 and x=0.1 respectively was attributed to an increase in the Fe-Fe exchange interactions. Moreover, magnetocaloric effect was calculated in terms of isothermal magnetic entropy change. The maximum values of （-△SM^max ） of La1-xBixFe11.4Si1.6 for x=-0.0 and 0.1 compounds were found to be, respectively, 22.56 and 4.36 J/（kg.K） under an applied magnetic field change of 5 T. For the same applied magnetic field （μ0H=5 T）, the relative cooling power （RCP） values were found to vary between 487 and 296 J/kg.

关键词： NaZn13 itinerant-electron metamagnetic transition magnetocaloric effects rare earths

Microstructural characterization and oxidation resistance of multicomponent equiatomic CoCrCuFeNi–Tio high-entropy alloy

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International Journal of Minerals,Metallurgy and Materials 2018年第11期25卷 1286-1293页

作者： Qing-dong Qin Jin-bo Qu Yong-e Hu Yu-jiao Wu Xiang-dong Su Key Laboratory of Light Metal Materials Processing Technology of Guizhou Province Guizhou Institute of TechnologyGuiyang 550003China Department of Materials&Metallurgy engineering Guizhou Institute of TechnologyGuiyang 550003China Merchant Marine college Shanghai Maritime UniversityShanghai 201306China 2011 Special Functional Materials Collaborative Innovation Center of Guizhou Province Guiyang 550003China

CoCrCuFeNi–Tio was prepared by arc melting of the pure elements and Ti_2Co powder under an Ar atmosphere. Both CoCrCuFe Ni and CoCrCuFeNi–Tio alloys are composed of a face-centered cubic(fcc) solid solution, whereas the alloys of CoCrCuFeNi–Tio are basically composed of an fcc solid solution and Tio crystals. The microstructures of CoCrCuFeNi–Tio are identified as dendrite and interdendrite structures such as CoCrCuFeNi. The morphology of Tio is identified as an equiaxed crystal with a small amount of added Ti_2Co. By increasing the amount of Ti_2Co added, the Tio content was dramatically increased and part of the equiaxed crystals changed to a dendrite structure. A test of the oxidation resistance demonstrates that the oxidation resistance of CoCrCuFeNi–Tio is better than that of CoCrCu Fe Ni. However, as the Tio content increases further, a corresponding decrease is observed in the oxidation resistance.

关键词： multicomponent equiatomic high-entropy alloys microstructure oxidation resistance

Robust reduction of graphene fluoride using an electrostatically biased scanning probe

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Nano Research 2013年第11期6卷 767-774页

作者： Woo-Kyung Lee Stanislav Tsoi Keith e. Whitener Rory Stine Jeremy T. Robinson Jonathon S. Tobin Asanka Weerasinghe Paul e. Sheehan Sergei F. Lyuksyutov Division of Chemistry US Naval Research Laboratory Washington DC20375 USA NoVA Research Alexandria Virginia 22308 USA Division of electronic Science and Technology US Naval Research Laboratory Washington DC 20375 USA The University of Akron Department of Physics Akron OH 44325 USA

We report a novel and easily accessible method to chemically reduce graphene fluoride （GF） sheets with nanoscopic precision using high electrostatic fields generated between an atomic force microscope （AFM） tip and the GF substrate. Reduction of fluorine by the electric field produces graphene nanoribbons （GNR） with a width of 105-1,800 nm with sheet resistivity drastically decreased from 〉1 TΩ.sq.^-1 （GF） down to 46 kΩ.sq.^-1 （GNR）. Fluorine reduction also changes the topography, friction, and work function of the GF. Kelvin probe force microscopy measurements indicate that the work function of GF is 180-280 meV greater than that of graphene. The reduction process was optimized by varying the AFM probe velocity between 1.2 μm.s^-1 and 12 μm.s^-1 and the bias voltage applied to the sample between -8 and -12 V. The electrostatic field required to remove fluorine from carbon is -1.6 ***-1. Reduction of the fluorine may be due to the softening of the C-F bond in this intense field or to the accumulation and hydrolysis of adventitious water into a meniscus.

关键词： graphene fluoride graphene electrostatic lithography Kelvin force probemicroscopy atomic force microscopy-based electrostaticnanolithography(AFMeN)

Use of HPHT Autoclave to Determine Corrosion Inhibition effect of Poly(methyl methacrylate-co-N-vinyl-2-pyrrolidone) on Carbon Steels in 3.5% NaCl Solution Saturated with Co_2

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Chinese Journal of Polymer Science 2015年第2期33卷 339-348页

作者： Ambrish Singh 林元华 Chun-yang Zhu Yuan-peng Wu eno e.ebenso State Key Laboratory of oil and Gas Reservoir Geology and exploitation Southwest Petroleum University Department of Chemistry School of Civil Engineering LFTS Lovely Professional University School of Material Science and engineering (Southwest Petroleum University) Department of Chemistry School of Mathematical & Physical Sciences North-West University(Mafikeng Campus)

The influence of poly（methylmethacrylate-co-N-vinyl-2-pyrrolidone）, P（MMA-co-VP）, on corrosion of carbon steels（J55, N80, P110 SS and C110 steels） in 3.5 wt% NaCl solution saturated with Co2 was evaluated using static high pressure and high temperature（HPHT） autoclave. The surface was further evaluated by X-ray diffraction（XRD）, scanning electron microscopy（SeM） and contact angle measurements. Quantum chemical calculations have been used to evaluate the structural, electronic and reactivity parameters of the inhibitor on the steels surface. SeM, XRD and contact angle measurement studies reveal that the surface of metals are quite unaffected after use of inhibitor in 3.5% NaCl solution saturated with Co2.

关键词： Polymer NMR Autoclave SeM XRD

Inside-out ostwald ripening： A facile process towards synthesizing anatase Tio2 microspheres for high- efficiency dye-sensitized solar cells

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Nano Research 2016年第7期9卷 1891-1903页

作者： Yong Ding Xin Xia Wangchao Chen Linhua Hu Li'e Mo Yang Huang Songyuan Dai Beijing Key Laboratory of Novel Thin-Film Solar Cells North China Electric Power University Beijing 102205 China Key Laboratory of Novel Thin-film Solar Cells Institute of Applied Technology Hefei Institutes of Physical Science Chinese Academy ot Sciences Hefei 230031 China

A facile inside-out ostwald ripening route to the morphology-controlled preparation of Tio2 microspheres is developed. Here, Tio2 hollow microspheres （HM） and solid microspheres （SM） are prepared by adjusting the volume ratio of isopropanol （IPA） to acetylacetone （Acac） in the solvothermal process. During the formation process of HM, precipitation of solid cores, subsequent deposition of outer shells on the surface of cores, and simultaneous core dissolution and shell recrystallizafion are observed, which validate the inside-out ostwald ripening mechanism. Design and optimization of the properties （pore size, surface area, and trap state） of Tio2 microspheres are vital to the high performance of dye- sensitized solar cells （DSSCs）. The optimized Tio2 rnicrospheres （rHM and rSM） obtained by post-processing on recrystallization, possess large pore sizes, high surface areas and reduced trap states （Ti3~ and oxygen vacancy）, and are thus ideal materials for photovoltaic devices. The power conversion efficiency of DSSCs fabricated using rHM photoanode is 11.22%, which is significantly improved compared with the 10.54% efficiency of the rSM-based DSSC. our work provides a strategy for synthesizing Tio2 microspheres that simultaneously accommodate different physical properties, in terms of surface area, crystallinity, morphology, and mesoporosity.

关键词： ostwald ripening dye-sensitized solar cell Tio2 microsphere hollow structure acetylacetone

Numerical study on polymer nanofibers with electrically charged jet of viscoelastic fluid in electrospinning process

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Journal of Central South University 2017年第10期24卷 2275-2280页

作者： P.Valipour H.Zaersabet M.Hatami Ali Zolfagharian S.e.Ghasemi Department of Textile and Apparel Qaemshahr BranchIslamic Azad UniversityQaemshahrIran Department of Mechanical engineering Esfarayen University of TechnologyEsfarayenNorth KhorasanIran School of engineering Deakin UniversityGeelongVictoria 3216Australia Young Researchers and elite Club Sari BranchIslamic Azad UniversitySariIran

electrospinning is a useful and efficient technique to produce polymeric nanofibers. Nanofibers of polymers are electrospun by creating an electrically charged jet of polymer solution. Numerical study on non-Newtonian and viscoelastic jets of polymer nanofibers in electrospinning process is presented in this work. In particular, the effect of non-Newtonian rheology on the jet profile during the electrospinning process is examined. The governing equations of the problem are solved numerically using the Keller-Box method. The effects of yield stress and power-law index on the elongation, velocity, stress and total force are presented and discussed in detail. The results show that by increasing the values of yield stress, the fluid elongation is reduced significantly.

关键词： nanofibers electrospinning electrically charged jet viscoelastic fluid synthetic polymers

Nitrogen enrichment alters carbon fluxes in a New england salt marsh

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ecosystem Health and Sustainability 2018年第11期4卷 34-44页

作者： emily K.Geoghegan Joshua S.Caplan Francine N.Leech Paige e.Weber Caitlin e.Bauer Thomas J.Mozdzer Department of Biology Bryn Mawr CollegeBryn MawrPAUSA

Introduction:Nitrogen enrichment of coastal salt marshes can induce feedbacks that alter ecosystem-level processes including primary production and carbon *** the rising interest in coastal blue carbon,the effects of chronic nutrient enrichment on blue carbon processes have rarely been measured in the context of experimental ***,we examined the ecosystem-level effects of nitrate(No3)enrichment on the green-house gas dynamics of a Spartina alterniflora-dominated salt *** measured Co2 and CH4 fluxes using static chambers through two growing seasons in a salt marsh that was nitrogen-enriched for 13 years and compared fluxes to those from a reference ***:We found that nitrogen enrichment increased gross primary productivity(GPP)by 7.7%and increased ecosystem respiration(Recd)by 20.8%.However,nitrogen enrichment had no discernible effect on net ecosystem exchange(Nee).Taken together,these results suggest that nitrogen-induced stimulation of Reco could transform this salt marsh from a carbon sink into a source of carbon to the atmos ***:our results complement prior findings of nitrogen enrichment weakening soil structure and organic matter stability in tidal salt marshes,suggesting that increased nutrient inputs have the potential to alter the carbon storage function of these ecosystems through enhanced microbial respiration of previously sequestered carbon.

关键词： Spartina alterniflora blue carbon eutrophication gross primaryproductivity net ecosystemexchange nitrogen ecosystem respiration tidalsaltmarsh

evaluation of Weed Incidence and Biomass in Coffee Intercropped with oil Palm in Avenue and Hollow Square Arrangement in Nigeria

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American Journal of Plant Sciences 2020年第2期11卷 276-284页

作者： A. o. Famaye S. A. Adeosun K. o. Ayegboyin K. B. Adejobi o. S. o. Akanbi A. F. okunade Cocoa Research Institute of Nigeria (CRIN) Ibadan Oyo State Nigeria

Weed incidence and biomass in tree crop plantations are mainly influenced by environmental, farm management practices and cropping systems. Manipulation of intercropping systems to improve weed management in coffee intercropped with oil palm requires a better understanding of spatial and temporal dynamics of weeds. To evaluate the effect of weed incidence and biomass in coffee intercropped with oil palm in avenue and hollow square arrangement, a study was carried out in Cocoa Research Institute of Nigeria (CRIN) in two locations. The locations are Idi-Ayunre (7°25'N, 3°24'e) (an alfisol) and Uhonmora (6°5'N, 5°50'e) (ultisol) in rainforest and derived savannah parts of Nigeria respectively. The experiment had three treatments comprising coffee sole (control), coffee with oil palm (Hollow square) arrangement and coffee with oil palm (Avenue) planting. Coffee was planted 3.0 m apart while oil palm was planted 9 m apart. equal size of land area was used for coffee in each treatment. The experimental design was Randomized Complete Block (RCBD) with three replicates. Data on vegetative growth of coffee, weed incidence and biomass were taken at three-monthly intervals. The result showed that coffee/oil palm (Hollow Square) had the least weed incidence and biomass closely followed by coffee/oil palm (Avenue) planting. The control had the highest weed biomass which was significantly different from Hollow square and Avenue planting at P ≤ 0.05. The morphological parameters on coffee followed the same pattern but Hollow square arrangement was significantly higher than Avenue and control at P ≤ 0.05.

关键词： evaluation Weed Incidence Biomass Coffee Intercropped oil Palm Hollow Square Avenue Arrangement