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Methane Oxidative Coupling over Fluoride-Promoted Cerium Oxide Catalysts

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Chemical research in Chinese Universities 1993年第3期9卷 264-268页

作者： k.r.Tsai Department of Chemistry Xiamen University Xiamen 361005ince the pioneer work of Keller and Bhasin on the oxidative coupling of methane many catalyst systems mostly based on the oxides or complex oxides of alkali metals alkali earth metals and rare earth metals have been developed. In some studies halides especially chlorides and bromides have been added to these oxides in order to improve the catalvtic activitv and selectivity. howevek of

Since the pioneer work of keller and Bhasin on the oxidative coupling of methane, many catalyst systems, mostly based on the oxides or complex oxides of alkali metals, alkali earth metals and rare earth metals, have been developed. In some studies, halides, especially chlorides and bromides, have been added to these oxides in order to improve the catalvtic activitv and selectivity. howevek of

关键词： Fluoride Oxidative coupling of methane Oxygen species Cerium oxide

Determination of pile failure mechanism under pullout test in loose sand

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Journal of Central South University 2015年第4期22卷 1490-1501页

作者： k.Faizi r.kalatehjari r.Nazir A.S.A.rashid Department of Geotechnics and Transportation Universiti Teknologi Malaysia

Estimating the deformation of soil around the pile contributes to reliable design of structures under pullout force. This work presents the results of a series of small-scale physical modelling tests designed to investigate the uplift resistance of piles with diameter of 5 cm and slenderness ratios of 1, 2, 3 and 4 in loose sand. Close photogrammetric technique and particle image velocimetry(PIV) were employed to observe the failure patterns due to uplift force on piles. The results show that the shear zones curve slightly outward near the ground surface. After peak resistance, the shear strain concentrates into a pair of narrow shear bands,then a flow around mechanism is formed accompanied by a reduction in the uplift resistance. The results from the laboratory tests were verified by analytical method proposed by Chattopadhyay and PLAXIS 2D and 3D finite element method software. It is found that the depth and width of the failure surface increase with the increment of the slenderness ratio. A good agreement is observed among the measured bearing capacity and obtained failure surface of the models and the results of numerical modelling. Finally, the maximum deformation of loose and dense sand respectively with densities of 25% and 75% were compared in the stage of fully removing pile. The results shows that the deformation of the soil is related to its density, therefore it depends on its dilatancy.

关键词： pile uplift sand particle image velocimetry

Light Weight Cryptographic Address Generation(LW-CGA) Using System State Entropy Gathering for IPv6 Based MANETs

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China Communications 2017年第9期14卷 114-126页

作者： reshmi T.r Murugan k VIT University Anna University

In IPv6 based MANETs, the neighbor discovery enables nodes to self-configure and communicate with neighbor nodes through autoconfiguration. The Stateless address autoconfiguration(SLAAC) has proven to face several security issues. Even though the Secure Neighbor Discovery(SeND) uses Cryptographically Generated Addresses(CGA) to address these issues, it creates other concerns such as need for CA to authenticate hosts, exposure to CPU exhaustion attacks and high computational intensity. These issues are major concern for MANETs as it possesses limited bandwidth and processing power. The paper proposes empirically strong Light Weight Cryptographic Address Generation(LW-CGA) using entropy gathered from system states. Even the system users cannot monitor these system states; hence LW-CGA provides high security with minimal computational complexity and proves to be more suitable for MANETs. The LW-CGA and SeND are implemented and tested to study the performances. The evaluation shows that LW-CGA with good runtime throughput takes minimal address generation latency.

关键词： IPv6 SLAAC EUI-64 CGA SEND system states MANETs

Drop weight impact analysis of GFrP tubes with hollow glass particle-filled matrix

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Defence Technology（防务技术） 2023年第11期29卷 1-9页

作者： Daniel Paul r.Velmurugan N.k.Gupta Department of Aerospace Engineering Indian Institute of Technology MadrasChennaiIndia Department of Applied Mechanics Indian Institute of Technology DelhiNew DelhiIndia

Protecting occupants or payloads in crashes and blasts is of utmost importance in both moving and immobile *** way of achieving this is by using a sacrificial energy *** tubes have been studied as potential energy absorbers due to their ability to fail progressively under axial *** this study,the energy absorption capability of these tubes is enhanced by adding hollow glass particles to the ***-weight tests are performed on composite tubes,and a digital image correlation(DIC)-based technique is used to capture their load-displacement *** eliminates the use of electronic data acquisition systems,load cells,and *** load-displacement curves of the tubes are obtained from the DIC-based technique and examined to understand their crushing *** the mean crush load shows a drop,an increase in crush length is *** specific energy absorbed by the tubes improves with an increase in GMB volume *** addition of 0.1,0.2,0.3 and 0.4 vol fractions of GMB results in the specific energy absorption increasing by6.6%,14.7%,24%and 36.6%,respectively,compared to neat glass fibre-epoxy *** examination of the tubes and comparison with tubes subject to quasi-static compression is also performed.

关键词： Composite tubes Syntactic foam Impact Axial compression Digital image correlation

A study of local amplification effect of soil layers on ground motion in the kathmandu Valley using microtremor analysis

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Earthquake Engineering and Engineering Vibration 2012年第2期11卷 257-268页

作者： Paudyal Y.r. Yatabe r. Bhandary N.P. Dahal r.k. Geo-disaster research Laboratory Graduate School of Science and EngineeringEhime UniversityEhimeMatsuyamaJapan

Past researchers have anticipated the occurrence of a great earthquake in the central Himalayas in the near *** may cause serious damage in the kathmandu Valley,which sits on an ancient lake bed zone,with lacustrine sediments of more than 500 m *** this study,the predominant frequency of ground motion is evaluated using the Horizontal-to-Vertical (H/V) spectral ratio technique and recordings of ambient *** results of the H/V ratio show two peaks in about 20 percent of the locations,which are distributed mainly in and around the center and northern part of the kathmandu *** predominant frequencies vary from 0.5 Hz to 8.9 Hz in the study area,whereas the second resonance fiequency varies from 4 Hz to 6 Hz in the center and northern part of the *** indicates that the center and northern part of the valley have a wide range of resonance frequency due to two levels of impedance contrast- one may be from the surface layer and the other may be from the layer *** two levels of resonance indicate the importance of considering the effects of surface and lower layers during the planning and designing of infrastructures in the kathmandu Valley.

关键词： microtremor predominant frequency resonance kathmandu Valley

Effect of root-Induced Chemical Changes on Dynamics and Plant Uptake of Heavy Metals in rhizosphere Soils

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Pedosphere 2010年第4期20卷 494-504页

作者： k.r.kIM G.OWENS r.NAIDU Climate Change & Agroecology Division Department of Agricultural EnvironmentNational Academy of Agricultural Science Centre for Environmental risk Assessment and remediation University of South Australia Cooperative research Centre for Contamination Assessment and remediation of the Environment

It is increasingly recognized that metal bioavailability is a better indicator of the potential for phytoremediation than the total metal concentration in soils; therefore, an understanding of the influence of phytoremediation plants on metal dynamics at the soil-root interface is increasingly vital for the successful implementation of this remediation technique. In this study, we investigated the heavy metal and soil solution chemical changes at field moisture, after growth of either Indian mustard （Brassica juncea） or sunflower （Helianthus annuus L.）, in long-term contaminated soils and the subsequent metal uptake by the selected plants. In addition, the fractions of free metal ions in soil solution were determined using the Donnan membrane technique. After plant growth soil solution pH increased by 0.2-1.4 units and dissolved organic carbon （DOC） increased by 1-99 mg L^-1 in all soils examined. Soluble Cd and Zn decreased after Indian mustard growth in all soils examined, and this was attributed to increases in soil solution pH （by 0.9 units） after plant growth. Concentrations of soluble Cu and Pb decreased in acidic soils but increased in alkaline soils. This discrepancy was likely due to a competitive effect between plant-induced pH and DOC changes on the magnitude of metal solubility. The fractions of free Cd and Zn ranged from 7.2% to 32% and 6.4% to 73%, respectively, and they generally decreased as pH and DOC increased after plant growth. Metal uptake by plants was dependant on the soil solution metal concentration, which was governed by changes in pH and DOC induced by plant exudates, rather than on the total metal concentrations. Although plant uptake also varied with metal and soil types, overall soluble metal concentrations in the rhizosphere were mainly influenced by root-induced changes in pH and DOC which subsequently affected the metal uptake by plants.

关键词： bioavailability phytoremediation speciation

Plasmonic enhancement of upconversion emission in Ag@NaYF4:Er^3+/Yb^3+phosphor

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Journal of rare Earths 2018年第9期36卷 903-910页

作者： S.k.Maurya S.r Tiwari A.kumar k.kumar Optical Materials and Bio-imaging research Laboratory Department of Applied PhysicsIndian Institute of Technology(Indian School of Mines)Dhanhad-826004India

In this article upconversion luminescence of silver nanoparticles（AgNPs） coated NaYF4：Er3＋/Yb3＋phosphor nano-particles was *** prepared samples were characterized through various *** surface plasmon band is observed for prepared AgNPs by analyzing UV-vis measurements and is used to enhance the upconversion *** the upconversion measurement the emission bands are observed at 522,546,and 656 nm corresponding to the 2 H11/2→ 4115/2,4 S3/2→4 I15/2and 4 F9/2→4 I15/2 levels,*** upconversion emission intensity of the above bands is found to enhance for sample containing 1 mmol *** time of 4 S3/2 and 4F9/2 levels is found to decrease on coating of AgNPs and hence intensity enhancement is assumed due to the surface plasmon resonance（SPr） effect.

关键词： Upconversion phosphor Surface plasmon resonance Decay time analysis CIE diagram rare earths

Spectroscopic investigations and luminescence spectra of Sm3+ doped soda lime silicate glasses

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Journal of rare Earths 2009年第5期27卷 773-780页

作者： Y.k. Sharma S.S.L. Surana r.k. Singh Department of Physics Govt. Post Graduate College Rudrapur 263153 (U S Nagar) India Department of Physics J. N. V. University Jodhpur-342001 India Department of Physics Govt. Post Graduate College Rudrapur 263153 (U S Nagar) India

Sm3+ doped soda lime silicate glasses co-doped with As2O3 were prepared and characterised by measuring their absorption spectra in UV-VIS/NIr regions and luminescence spectra in the visible region. Judd-Ofelt intensity parameters, Ωλ, were evaluated from the measured intensities of the various absorption bands. Ωλ parameters of these glasses were compared with the Ωλ parameters of other reported Sm3+ glasses to study the bonding environment surrounding the Sm3+ in the present glasses. Presence of [AsO4]3– tetrahedra in the second coordination sphere around the central Sm3+ ion made these glasses less covalent as compared to other oxide glasses but the ratio Ω4/Ω6 of the 1.83 indicated them to be fairly stable. With the help of Ωλ parameters and luminescence data for various emission lines, radiative properties for different emission lines were calculated. The values of radiative properties indicated that 4G5/2→6H7/2 and 4G5/2→6H9/2 transitions responsible for orange luminescence might be used in the development of materials for LED's and other optical devices in the visible region.

关键词： rare earth glasses Judd-Ofelt theory absorption spectroscopy luminescence

Exacerbation of Soft Tissue Lesions in Lead Exposed Virus Infected Mice

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Biomedical and Environmental Sciences 2003年第4期16卷 369-378页

作者： PrATIBHAGUPTA M.M.HUSAIN rAVISHANkErt r.k.S.DOGrA P.k.SETH r.k.MAHESHWArI PrATIBHAGUPTAt VirologyLaboratory IndustrialToxicologyResearchCentreP.O.BoxNo.80MahatmaGandhiMargLucknow226001lndia DepartmentofPathology UniformedServicesUniversityofHealthSciences4301JonesBridgeRoadBethesdaMD20814USA

Objective To investigate the effect of Lead (Pb) acetate exposure on Semliki forest virus (SFV) pathogenesis in mice. Methods Different doses (62.5, 125, 250 and 500 mg/kg body weight) of Pb dissolved in normal saline were given to mice by oral intubation in a sub-acute (28 days) and sub-chronic (90 days) regimen followed by SFV infection. Morbidity, mortality, clinical symptoms, mean survival time (MST), changes in body and organ weight, accumulation of lead in soft tissues, virus titre in brain and histopathological alterations were compared between lead exposed and infected groups. results Early appearance of virus symptoms, increased mortality, decreased MST, enhanced SFV titre and greater tissue damage were observed in lead exposed-SFV-infected mice. Conclusion Pre-exposure to lead increases the susceptibility of mice towards SFV infection. Further studies are suggested in view of the persistence of lead in the environment and the possibility of infection by microbial pathogens.

关键词： Lead acetate Exposure Sub-acute Sub-chronic SFV Pathogenicity