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Mechanical and corrosion behaviour of hydroxyapatite reinforced Mg-Sn alloy composite by squeeze casting for biomedical applications

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Journal of Magnesium and Alloys 2020年第2期8卷 452-460页

作者： r radha d.Sreekanth School of Mechanical and Building Sciences Vellore Institute of TechnologyChennai 600127India

Magnesium alloys have gained increasing attention for biomedical applications due to their biocompatibility and the ***(HA)is known to be a highly bioactive because of its similar chemical and crystallographic structures to ***,HA is believed to be a potential ceramic material for the fabrication of Mg based composites,to combine the advantages of both Mg and ***,in general,the composites known to be more susceptible to corrosion attack than the matrix ***,in the present work,Sn is used as an alloying element to evaluate its effect on mechanical as well as corrosion properties of Mg/HA *** with 5 wt%HA and Mg-1 wt%Sn-5 wt%HA composites were prepared separately by stir assisted squeeze casting *** phase analysis and microstructure were characterized by X-ray diffraction(Xrd)and scanning electron microscope(SEM)coupled with energy dispersive spectroscopy(EdS)*** properties were evaluated by conducting the compression and micro hardness *** properties of as-cast composites were studied by linear polarization,Tafel and electrochemical impedance spectroscopy(EIS)*** results of both Xrd and SEM-EdS revealed that the main constitutional phases of as-cast Mg/HA composites were a-Mg and HA whereas,in Mg-Sn/HA composites,the phase Mg^Sn was observed along with fine distribution of HA *** both the cases,no interfacial reactions *** yield strength,ultimate compression strength and hardness were found to be increased with the addition of Sn in Mg/HA ***,the addition of Sn also played an important role in increasing the corrosion resistance of the Mg/HA composites which was attributed the refinement of grain size and the formation of Mg2Sn phase along the grain ***,it was concluded that the addition of Sn improves both mechanical and corrosion properties of Mg/HA composites.

关键词： Magnesium Composite Biomedical Corrosion Squeeze casting

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Luminescence properties of Gd^(3+) containing glasses for ultra-violet(UV) light

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Journal of rare Earths 2014年第5期32卷 389-393页

作者： d.d.ramteke r.S.Gedam department of Applied Physics Visvesvaraya National Institute of Technology

Effect of Gd2O3 addition on optical properties of 27.5 Li2O-72.5 B2O3 glass systems was studied. density, differential thermal analysis （dTA）, optical absorption spectra and luminescence technique were used to characterize the prepared glasses. Emis- sion spectra showed two band 6p7/2→8S7/2 （311.5 nm） and 6p5/2→8S7/2 （305 nm） under the excitation of 274 nm. The intense emission at 311.5 nm suggested that these glasses could be useful as source of narrowband UV light.

关键词： glasses rare earths absorption band gap luminescence UV light

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Electrical and optical properties of lithium borate glasses doped with Nd_2O_3

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Journal of rare Earths 2012年第8期30卷 785-789页

作者： r.S. Gedam d.d. ramteke department of Applied Physics Visvesvaraya National Institute of Technology

Glass series with general formula 25Li2O-（75-x）B2O3-xNd2O3 was prepared by conventional melt quench technique. Electrical and optical characterizations of these glasses were carried out. It was observed that conductivity of glasses decreased and activation energy in- creased with the addition of Nd2O3. The density and refractive index of the glasses increased while optical band gap and radiation length de- creased due to structural changes.

关键词： conductivity density refractive index optical absorption Tauc's plot rare earths

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radiotherapy-customized head immobilization masks:from modeling and analysis to 3d printing

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Nuclear Science and Techniques 2019年第9期30卷 103-118页

作者： M.A.r.Loja d.S.Craveiro L.Vieira E.Sousa J.A.rodrigues r.J.F.Portal CIMOSM Centro de Investigacao em Modelacao e Optimizacao de Sistemas Multifuncionais ISEL IPL Instituto Superior de Engenharia de Lisboa Av. Conselheiro Emidio Navarro 1 1959-007 Lisbon Portugal LAETA IDMEC Instituto Superior Teccnico Universidade de Lisboa Av. Rovisco Pais 1 1049-001 Lisbon Portugal department of Mechanical and Industrial Engineering Faculty of Science and Technology NOVA UNIDEMI Universidade Nova de Lisboa Caparica Portugal H&TrC -Health &Technology research Center ESTeSL - Escola Superior de Tecnologia da Saude de Lisboa Av. D. Joao II Lote 4.69.01 1990-096 Lisbon Portugal Instituto de Biofisica e Engenharia Biomedica Faculdade de Ciencias da Universidade de Lisboa Lisbon Portugal

Immobilization devices may be a valuable aid to ensure the improved effectiveness of radiotherapy treatments where constraining the movements of specific anatomical segments is crucial. This need is also present in other situations, specifically when the superposition of various medical images is required for fine identification and characterization of some pathologies. Because of their structural characteristics, existing head immobilization systems may be claustrophobic and very uncomfortable for patients, during both the modeling and usage stages. Because of this, it is important to minimize all the discomforts related to the mask to alleviate patients’ distress and to simultaneously guarantee and maximize the restraint effectiveness of the mask. In the present work, various head immobilization mask models are proposed based on geometrical information extracted from computerized tomography images and from 3d laser scanning point clouds. These models also consider the corresponding connection to a radiotherapy table, as this connection is easily altered to accommodate various manufacturers’ solutions. A set of materials used in the radiotherapy field is considered to allow the assessment of the stiffness and strength of the masks when submitted to typical loadings.

关键词： Computed tomography 3d laser scanning Geometric modeling Head immobilization devices Stiffness and strength analyses 3d printing

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Effects of Nano-Y_2O_3 and Sintering Parameters on the Fabrication of PM duplex and Ferritic Stainless Steels

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Acta Metallurgica Sinica(English Letters) 2016年第1期29卷 58-71页

作者： r.Shashanka d.Chaira department of Metallurgical and Materials Engineering National Institute of Technology

Here we report the effects of nano-Y203 addition, sintering atmosphere and time during on the fabrication of PM duplex and ferritic stainless steels composites by dual-drive planetary milling of elemental Fe, Cr and Ni powders followed by conventional pressureless sintering. Yttria-free and yttria-dispersed duplex and ferritic stainless steels are fabricated by conventional sintering at 1000, 1200 and 1400 ℃ temperatures under argon atmosphere. In another set of experiment, yttria-free and yttria-dispersed duplex and ferritic stainless steels are consolidated at 1000 ℃ for l h under nitrogen atmosphere to study the effect of sintering atmosphere. It has been found that densities of duplex and yttria- dispersed duplex stainless steel increase from 71% to 91% and 78% to 94%, respectively, with the increase in sintering temperature. Similarly, hardness value increases from 257 to 567 HV25 in case of duplex, and from 332 to 576 HV25 in yttria-dispersed duplex stainless steel. X-ray diffraction analysis shows the domination of more intense austenite phase than ferrite at higher sintering temperature and also in nitrogen atmosphere. It is also evident that addition of yttria enhances phase transformation from a-Fe to 7-Fe. duplex and yttria-dispersed duplex stainless steels exhibit the maximum com- pressive yield strength of 360 and 312 MPa, respectively.

关键词： Nano-Y2O3 Composites Stainless steel Powder metallurgy (PM) Mechanical properties Microstructure Phase transitions

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Magnetic susceptibility measurements on metakaolin admixtured cement hydrated with ground water and sea water

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International Journal of Minerals,Metallurgy and Materials 2009年第3期16卷 349-354页

作者： d. Govindarajan r. Gopalakrishnan department of Physics Annamalai University Annamalai Nagar608002 Tamilnadu India

The role of metakaolin in the properties of Portland cement hydrated with ground water and sea water was described by magnetic susceptibility study. Cement pastes containing 0wt%, 10wt%, 20wt% and 30wt% replacement of metakaolin and in a water/cement （W/C） ratio of 0.4 were prepared. The susceptibility at different hydration periods was determined by Faraday Curie balance and it was related to the changes in setting time and compressive strength of admixtured cement. Compared with sea water-treated cement paste, the magnetic susceptibility of ground water-treated cement paste is higher in value. The observed result shows that, irrespective of water, the magnetic susceptibility increases with increasing metakaolin percentage replacement level in cement.

关键词： magnetic susceptibility admixtured cement hydration pozzolanic activity sea water

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Landslide inventory validation and susceptibility mapping in the Gerecse Hills, Hungary

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Geo-Spatial Information Science 2021年第3期24卷 498-508页

作者： dávid Gerzsenyi Gáspár Albert department of Cartography and Geoinformatics Eötvös Loránd UniversityBudapestHungary

Landslides pose a threat to property both in the populated and cultivated areas of the Gerecse Hills (Hungary). The currently available landslide inventory database holds the records from many sites in the area, but the database is out-of-date. Here we address the problem of revising the National Landslides Cadastre landslide inventory database by creating a landslide suscept-ibility map with a multivariate model based on likelihood ratio functions. The model is applied to the TandEM-X dEM (0.4″ res.), the current landslide inventory of the area, and data acquired from geological maps. By comparing the distributions of four variables in the landslide and non-landslide area with grid computation methods, the model yields landslide susceptibility estimates for the study area. The estimations show to what extent a certain area is similar to the sample areas, therefore, its likelihood to be affected by landslides in the future. The accuracy of the model predictions was checked in the field and compared to the results of our previous study using the SrTM-1 dEM for a similar analysis. The model gave accurate estimates when certain correction measures were applied to the input datasets. The limitations of the model, the input datasets, and the suggested correction measures are also discussed.

关键词： Landslide susceptibility landslide inventory TandEM-X Gerecse Hills landslides geomorphometry

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Machine learning enabled autonomous microstructural characterization in 3d samples

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npj Computational Materials 2020年第1期6卷 1654-1662页

作者： Henry Chan Mathew Cherukara Troy d.Loeffler Badri Narayanan Subramanian K.r.S.Sankaranarayanan Center for Nanoscale Materials Argonne National LaboratoryArgonneILUSA department of Mechanical Engineering University of LouisvilleLouisvilleKYUSA department of Mechanical and Industrial Engineering University of Illinois at ChicagoChicagoILUSA

We introduce an unsupervised machine learning(ML)based technique for the identification and characterization of microstructures in three-dimensional(3d)samples obtained from molecular dynamics simulations,particle tracking data,or *** technique combines topology classification,image processing,and clustering algorithms,and can handle a wide range of microstructure types including grains in polycrystalline materials,voids in porous systems,and structures from self/directed assembly in soft-matter complex *** technique does not require a priori microstructure description of the target system and is insensitive to disorder such as extended defects in polycrystals arising from line and plane *** demonstrate quantitively that our technique provides unbiased microstructural information such as precise quantification of grains and their size distributions in 3d polycrystalline samples,characterizes features such as voids and porosity in 3d polymeric samples and micellar size distribution in 3d complex *** demonstrate the efficacy of our ML approach,we benchmark it against a diverse set of synthetic data samples representing nanocrystalline metals,polymers and complex fluids as well as experimentally published characterization *** technique is computationally efficient and provides a way to quickly identify,track,and quantify complex microstructural features that impact the observed material behavior.

关键词： microstructure polycrystalline porosity

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Characterization of water-in-crude oil emulsions in oil spill response

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Journal of Environmental Sciences 2003年第4期15卷 506-509页

作者： MATHEr r.r. FOTHErINGHAM A.F. YANG r.d. HeriotWattUniversityScottishBordersCampus HeriotWattUniversityScottishBordersCampusHeriotWattUniversityScottishBordersCampus GalashielsUKGalashielsUKGalashielsUK

The formation of water in crude oil emulsions occurs when crude oils are spilled into sea. The water in crude oil emulsions significantly change the properties of the spilled crude oils and in turn influence the choices made relating to oil spill countermeasures. The water in crude oil emulsions were characterized using various techniques in this study. The environmental scanning electron microscopy observation of water droplets in the emulsions is also presented. It is a powerful tool in emulsion observations.

关键词： oil spill water in oil emulsions oil spill response dSC ESEM

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Universality of a Critical Magnetic Field in a Holographic Superconductor

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Chinese Physics Letters 2015年第4期32卷 113-117页

作者： d.Momeni r.Myrzakulov Eurasian International Center for Theoretical Physics and department of General and Theoretical Physics Eurasian National University

We study aspects of holographic superconductors analytically in the presence of a constant external magnetic field. It is shown that the critical temperature and the critical magnetic field can be calculated at nonzero temperature. We detect the Meissner effect in such superconductors. A universal relation between black hole mass and critical magnetic field Hc is proposed to be Hc/M2/3≤0.687365. We also discuss some aspects of phase transition in terms of black hole entropy and Bekenstein＇s entropy to the energy upper bound.

关键词： Entropy

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