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Corrosion behavior of ultrafine-grained AA2024 aluminum alloy produced by cryorolling

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International Journal of Minerals,Metallurgy and Materials 2017年第11期24卷 1293-1305页

作者： P. Laxman Mani k.nta V.C. Srivastava k. Venk.teswarlu Sharma Paswan B. Mahato Goutam Das k. Sivaprasad k. Gopala k.ishna Department of Metallurgical & Materials Engineering National Institute of Technology Thiruchirappalli 620015 India National Metallurgical Laboratory Council of Scientific & Industrial Research Jamshedpur 831007 India National Aerospace Laboratories Council of Scientific & Industrial Research Bangalore 560017 India

The objectives of this study were to produce ultrafine-grained(UFG) AA2024 aluminum alloy by cryorolling followed by aging and to evaluate its corrosion behavior. Solutionized samples were cryorolled to ~85% reduction in thick.ess. Subsequent aging resulted in a UFG structure with finer precipitates of Al_2CuMg in the cryorolled alloy. The(1) solutionized and(2) solutionized and cryorolled samples were uniformly aged at 160°C/24 h and were designated as CGPA and CRPA, respectively; these samples were subsequently subjected to corrosion studies. Potentiodynamic polarization studies in 3.5 wt% NaCl solution indicated an increase in corrosion potential and a decrease in corrosion current density for CRPA compared to CGPA. In the case of CRPA, electrochemical impedance spectroscopic studies indicated the presence of two complex passive oxide layers with a higher charge transfer resistance and lower mass loss during intergranular corrosion tests. The improved corrosion resistance of CRPA was mainly attributed to its UFG structure, uniform distribution of fine precipitates, and absence of coarse grain-boundary precipitation and associated precipitate-free zones as compared with the CGPA alloy.

关键词： AA2024 alloy cryorolling ultrafine grains precipitation corrosion behavior

Characterization of a Microhollow Cathode Discharge Plasma in Helium or Air with Water Vapor

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Plasma Science and Technology 2013年第2期15卷 129-132页

作者： D. FUk.HARA S. NAMBA k. k.ZUE T. YAMASAk. k. TAk.YAMA Graduate school of Engineering Hiroshima University1-4-1 KagamiyamaHigashi-HiroshimaHiroshima 739-8527Japan

Microhollow cathode discharge （MHCD） plasmas were generated in gas mixtures containing water vapor at pressures of up to 100 k.a of He or 20 k.a of air. The cathode diameter was 1.0 mm with a length of 2.0 ram. The electricM characteristics showed an abnormal glow mode. Spectroscopic measurements were carried out to examine the plasma and radicals. An analysis of the spectral profile of Ha at 656.3 nm enabled a derivation of the electron densities, namely 2× 1014 cm-3 （at 10 k.a） and 6× 1014 cm-3 （at 4 k.a） for the helium and air atmospheres, respectively, in the negative glow region. By comparing the observed OH radical spectra with those calculated by the simulation code L[FBASE, the gas temperature was deduced to be 900 k.for 4 k.a of He at a discharge current of 50 mA.

关键词： microhollow cathode discharge atmospheric pressure plasma plasma spec-troscopy

Surfactant assisted solvothermal synthesis of ZnO nanoparticles and study of their antimicrobial and antioxidant properties

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Journal of Materials Science & Technology 2018年第6期34卷 1035-1043页

作者： Mina Zare k. Namratha k. Byrappa D.M. Surendra S. Yallappa Basavaraj Hungun Centre for Materials Science and Technology Vijnana Bhavan University of Mysore 570006 India DOS in Earth Science University of Mysore Vijnana Bhavan Manasagangotri Mysore 570 006 India Dept. of Chemistry Gokhale Centenary College Ankola 581314 Uttara Kannada India Department ofBiotechnology KLE Technological University Hubballi 580031 India

This study demonstrated a solvothermal method of growth of three different morphologies of zinc oxide nanoparticles （ZnO NPs）： i） flower-lik. nanorod and nanoflak.s, ii） assembled hierarchical structure, and iii） nano granule. Oleic acid （C18H3402）, gluconic acid （C6H1207） and tween 80 （C64H124026） were used as surfactant/capping/reducing agent for the formation of different morphologies of nanoparticles. The as-synthesized ZnO NPs were characterized by different physicochemical techniques such as UV-vis （UV-vis） spectroscopy, X-ray diffraction （XRD）, fourier transform infrared spectroscopy （FFIR）, field emission scanning electron microscopy （FE-SEM）, energy dispersive X-ray （EDX） analysis and dynamic light scattering （DLS） studies. Further, the antioxidant and antimicrobial activity of these nanostructures was evaluated. The antioxidant activity of these nanostructures was assessed via 2,2-diphenyl,1-1 picrylhydrazyl （DPPH）, 2,2＇-azino-bis （3-ethylbenzothiazoline-6-sulphonic acid）（ABTS） and H202 free radical scavenging activity. The in vitro antimicrobial activity of the obtained nanostructures was demonstrated against both gram negative （Escherichia coil） and gram positive （Staphylococcus aureus） bacterial genera. This study revealed antioxidant and antimicrobial properties of different structures ofZnO NPs suggesting their biomedical and industrial applications.

关键词： ZnO nanoparticles Solvothermal method Nanorods Nanoflak.s[k.Nano granule Antioxidant & antimicrobial studies

Adaptations of phytoplank.on in the Indian Ocean sector of the Southern Ocean during austral summer of 1998-2014

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Frontiers of Earth Science 2015年第4期9卷 742-752页

作者： R. k. MISHRA R. k. NAIk.N. ANIL k.MAR ESSO-National Centre for Antarctic and Ocean Research Ministry of Earth Sciences (MoES) Vasco-da-Gama Goa India

This study investigates the effects of light and temperature on the surface water diatoms and chloro- phytes, phytoplank.on in the Indian Ocean sector of the Southern Ocean （SO） during the austral summer of 1998- 2014. Significant longitudinal variations in hydrographic and biological parameters were observed at the Sub tropical front （STF）, Sub Antarctic front （SAF） and Polar front （PF） along 56°E-58°E. The concentrations of total surface chlorophyll a （Chl a）, diatoms, and chlorophytes measured by the National Aeronautics Space Agency （NASA） estimated by the Sea-Viewing Wide Field-of- View Sensors （SeaWiFS）, the Moderate Resolution Imaging Spectro Radiometer （MODIS）, and the NASA Ocean Biological Model （NOBM） were used in the study. Variations in the concentration of total Chl a was remark.ble amongst the fronts during the study period. The contribution of diatoms to the total concentration of surface Chl a increased towards south from the STF to the PF while it decreased in the case of chlorophytes. The maximum photosynthetically active radiation （PAR） was observed at the STF and it progressively decreased to the PF through the SAF. At the PF region the contribution of diatoms to the total Chl a biomass was ≥80%. On the other hand, the chlorophytes showed a contrary distribution pattern with ≥ 70% of the total Chl a biomass recorded at the STF which gradually decreased towards the PF, mainly attributed to the temperate adaptation. This clearly reveals that the trend of diatoms increased at the STF and decreased at the SAF and the PF. Further, the trend of chlorophytes was increased at the STF, SAF and PF with a shift in the community in the frontal system of the Indian Ocean sector of the SO.

关键词： chlorophyll a diatoms chlorophytes SST,PAR Southern Ocean

Supra-angular biopsy is more reliable for atrophy recognization:analysis of 1598 cases for gastric mucosal histological examination

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World Journal of Gastroenterology 2000年第6期6卷 893-897页

作者： Nobutak. yamada Department of Pathology First Hospital of Nippon Medical SchoolTokyoJapan

INTRODUCTIONChronic gastritis might be a disease of the highestmorbidity in the *** Warren and Marshallsuccessfully isolated and cultured Helicobacter pylori(***)from a gastric antrum biopsy,intensive researches produ... 详细信息

关键词： Helicobacter pylori gastric mucosa/pathology biopsy gastroscopy gastritis atrophic/pathology metaplasia

Effect of Post Heat Treatment on Corrosion Resistance of Phytic Acid Conversion Coated Magnesium

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Journal of Materials Science & Technology 2013年第2期29卷 180-186页

作者： R.k. Gupta k. Mensah-Dark.a D. k.mar Engineering Research Center for Revolutionizing Metallic Biomaterials (ERC-RMB) Department of Mechanical Engineering North Carolina A&T State University 1601 East Market Street Greensboro NC 27411 USA

An environment friendly chemical conversion coating for magnesium was obtained by using a phytic acid solution. The effect of post-coating 1heat treatment on the microstructures and corrosion properties of phytic acid conversion coated magnesium was investigated. It was observed that the microstructure and corrosion resistive properties were improved for the heat treated samples. The corrosion current density for bare magnesium, phytic acid conversion coated magnesium, and post-coating heat treated magnesium was calculated to be 2.48 ×10^-5, 1.18×10^-6, and 9.27 × 10^7 A/cm^2, respectively. The lowest corrosion current density for the heat treated sample indicated its highest corrosion resistive effect for the magnesium. The maximum corrosion protective nature of the heat treated sample was further confirmed by the largest value of impedance in electrochemical impedance spectroscopy studies.

关键词： Magnesium Phytic acid Corrosion Impedance spectroscopy Scanning electron microscopy

A survey on sensor localization

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控制理论与应用（英文版） 2010年第1期8卷 2-11页

作者： Jing WANG R. k. GHOSH Sajal k. DAS Center for Research in Wireless Mobility and Network.ng (CReWMaN) Department of Computer Science and Engineering University of Texas at Arlington Arlington TX 76019 USA Department of Computer Science and Engineering Indian Institute of Technology Kanpur India 208016

Localization is one of the fundamental problems in wireless sensor network. （WSNs）, since locations of the sensor nodes are critical to both network.operations and most application level task.. Although the GPS based localization schemes can be used to determine node locations within a few meters, the cost of GPS devices and non-availability of GPS signals in confined environments prevent their use in large scale sensor network.. There exists an extensive body of research that aims at obtaining locations as well as spatial relations of nodes in WSNs without requiring specialized hardware and/or employing only a limited number of anchors that are aware of their own locations. In this paper, we present a comprehensive survey on sensor localization in WSNs covering motivations, problem formulations, solution approaches and performance summary. Future research issues will also be discussed.

关键词： Sensor localization Wireless sensor network. Range measurements Anchors Mobile sensor Proba-bilistic localization

Standardization of harvesting age of bamboo shoots with respect to nutritional and anti-nutritional components

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Journal of Forestry Research 2013年第1期24卷 83-90页

作者： Ashok.k. Pandey Vijayalak.hmi Ojha Tropical Forest Research Institute Indian Council of Forestry Research and EducationP.O. RFRCMandla RoadJabalpur- 482 021India.

Bamboo shoots can be harvested at different ages but the data on the changes in nutritional composition with age are scanty. We standardized harvesting age of bamboo shoots in central India to obtain best quality produce with respect to nutritional composition. The shoots harvested on different days （2–20 days after emergence from ground） were analyzed for their nutritional （dietary fibres, carbohydrates, proteins, total phenols, ascorbic acid, sodium, potassium, phosphorus, calcium, magnesium and phenolic acids） and anti nutritional （cyanogen） constituents. A significant variation （at p ≤ 0.5） was observed in the nutritional composition of shoots of Dendrocalamus asper, D. strictus and Bambusa tulda harvested at different days. An overall decrease was observed in proteins and total phenols while dietary fibres and carbohydrates increased with ages. Significant variation （at p ≤ 0.5） was also observed in phenolic acids while minerals did not vary significantly. Results revealed that the optimum harvesting age for D. asper, D. strictus and B. tulda was on 10–14 days, 6–10 days and 10–16 days （after emergence from the ground） respectively. These results can be used to obtain quality bamboo shoots.

关键词： Bamboo shoots harvesting nutritional status central India phenolic acids anti-nutrient

Toward managing mixed-species stands： from parametrization to prescription

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Forest Ecosystems 2017年第4期4卷 286-302页

作者： Hans Pretzsch Eric k. Zenner Chair for Forest Growth and Yield Science Center of Life and Food Sciences Weihenstephan Technical University of Munich Hans-Carl-von Carlowitz-Platz 2 85354 Freising Germany

A better understanding and a more quantitative design of mixed-species stands will contribute to more integrative and goal-oriented research in mixed-species forests. Much recent work.has indicated that the structure and growth of mixed species forests may fundamentally differ from monocultures. Here we suggest how to progress from the present accumulation of phenomenological findings to a design of mixed-species stands and advanced silvicultural prescriptions by means of modelling. First, the k.owledge of mixing effects on the structure and growth at the stand, species, and individual tree level is reviewed, with a focus on those findings that are most essential for suitable modelling and silvicultural designs and the regulation of mixed stands as opposed to monocultures. Then, the k.y role of growth models, stand simulators, and scenario assessments for designing mixed species stands is discussed The next section illustrates that existing forest stand growth models require some fundamental modifications to become suitable for both monocultures and mixed-species stands. We then explore how silvicultural prescriptions derived from scenario runs would need to be both quantified and simplified for transfer to forest management and demonstrated in training plots. Finally, we address the main remaining k.owledge gaps that could be remedied through empirical research.

关键词： Multiplicative mixing effects Overyielding Overdensity Modelling mixing effects Scenario analysis,Silvicultural prescriptions Practical guidelines