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Understanding the mechanisms of friction stir welding based on computer simulation using particles

Defence Technology（防务技术） 2018年第6期14卷 643-656页

作者： A.Yu.smolin E.v.shilko s.v.Astafurov E.A.Kolubaev G.M.Eremina s.G.Psakhie Institute of strength Physics and Materials science sB ras Tomsk634055Russia Tomsk state University Tomsk634050Russia skolkovo Institute of science and Technology Skolkovo143025Russia

Friction stir welding(FsW) is a novel technique for joining different materials without melting. In FsW the welded components are joined by stirring the plasticized material of the welded edges with a special rotating pin plunged into the material and moving along the joint line. From the scientific point of view,the key role of the FsW processes belongs to formation of the special plasticized conditions and activation of physical mechanisms of mixing the materials in such conditions to produce the strong homogeneous weld. But it is still a lack of complete understanding of what are these conditions and *** paper is devoted to understanding the mechanisms of material mixing in conditions of FsW based on a computer simulation using particles. The movable cellular automaton method(MCA), which is a representative of the particle methods in mechanics of materials, was used to perform all ***, material flow including material stirring in FsW is simulated using computational fluid mechanics or smoothed particle hydrodynamics, which assume that the material is a continuum and does not take into account the material structure. MCA considers a material as an ensemble of bonded particles. Breaking of inter-particle bonds and formation of new bonds enables simulation of crack nucleation and healing, as well as mass mixing and *** paper consists of two main parts. In the first part, the simulations in 2 D statements are performed to study the dynamics of friction stir welding of duralumin plates and influence of different welding regimes on the features of the material stirring and temperature distribution in the forming welded joints. It is shown that the ratio of the rotational speed to the advancing velocity of the tool has a dramatic effect on the joint quality. A suitable choice of these parameters combined with additional ultrasonic impact could considerably reduce the number of pores and microcracks in the weld without significa

关键词： Friction stir welding Plastic flow Deformation mechanisms simulation Particle method

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The sytykanskaya kimberlite pipe:Evidence from deep-seated xenoliths and xenocrysts for the evolution of the mantle beneath Alakit,Yakutia,Russia

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Geoscience Frontiers 2015年第5期6卷 687-714页

作者： I.v.Ashchepkov A.M.Logvinova L.F.Reimers T.Ntaflos Z.v.spetsius N.v.vladykin H.Downes D.s.Yudin A.v.Travin L.v.Makovchuk v.s.Palesskiy O.s.Khmel'nikova Institute of Geology and Mineralogy sB ras vienna University Alrosa stock Company Institute of Geochemistry sB ras Birkbeck College University of LondonUKMalet Street

Mantle xenoliths（>150） and concentrates from late autolithic breccia and porphyritic kimberlite from the sytykanskaya pipe of the Alakit field（Yakutia） were analyzed by EPMA and LAM ICP *** P-TX-f（O2） diagrams minerals from xenoliths show widest variations,the trends P-Fe#-CaO,f（O2）for minerals from porphyric kimberlites are more stepped than for xenocrysts from *** PTX points mark moving for protokimberlites from the lithosphere base（7.5 GPa） to pyroxenite lens（5-3.5 GPa） accompanied by Cr increase by AFC and creation of two trends P-Fe#OI10-12%and13-15%.The Opx-Gar-based mantle geotherm in Alakit field is close to 35 mW/m2 at 65 GPa and 600 C near Moho was *** oxidation state for the megacrystalline ilmenites is lower for the metasomatic associations due to reduction of protokimberlites on peridotites than for uncontaminated varieties at the lithosphere *** inclined linear REE patterns with deep HFsE troughs for the parental melts of clinopyroxene and garnet xenocrysts from breccia were influenced by differentiated *** for metasomatic xenoliths reveal less inclined slopes without deep troughs in spider *** reveal s-shaped REE *** clinopyroxenes from graphite bearing Cr-websterites show inclined and inflected in Gd spectrums with LREE variations due to AFC *** for garnets display less inclined patterns and Ba-sr troughs but enrichment in ***40Ar/39Ar ages for micas from the Alakit mantle xenoliths for disseminated phlogopites reveal Proterozoic（1154 Ma） age of metasomatism in early Rodinia *** glimmerites with richterite- like amphiboles mark1015 Ma plume event in Rodinia ***600-550 Ma stage manifests final Rodinia *** last 385 Ma metasomatism is protokimberlite-related.

关键词： Kimberlites Mantle lithosphere Mantle xenoliths Th

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Amur Gold-Bearing Belt: Geotectonic Position and Perspectives for Revealing New Deposits of Precious Metals

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Global Geology 1999年第2期4卷 179-186页

作者： Khomich v.G. and Utkin v.P. (Far East Geological Institute of FEB ras vladivostok, 690022, Russia )

The ore-bearing belts, specialized for precious metals, are substantia ted to exist in the south Far East of Russia. The longest of which is the Amursk y gold-bearing belt extended from the Amur River mouth to the Ussuri River lowe r course and further to the southwest on China territory, probably, to the sungar i River head. The fact that we have distinguished the Amursky and other gold-be a ring belts, make it possible to reevaluate the perspectives of the south Far Eas t of Russia and North-East China for new deposits of precious metals.

关键词： gold-bearing belt geotectonic position perspective Am ur

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variable retention harvesting: conceptual analysis according to different environmental ethics and forest valuation

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Ecological Processes 2019年第1期8卷 485-491页

作者： Leonardo Galetto Carolina Torres Guillermo J.Martínez Pastur Departamento de Diversidad Biológica y Ecología FCEFyNUniversidad Nacional de Córdoba(UNC)Vélez Sarsfield 16115000 CórdobaArgentina Instituto Multidisciplinario de Biología vegetal(IMBIv) Consejo Nacional de Investigaciones Científicas y Técnicas(CONICET)Vélez Sarsfield 16115000 CórdobaArgentina Centro Austral de Investigaciones Científicas(CADIC) Consejo Nacional de Investigaciones Científicas y Técnicas(CONICET)Houssay 2009410 UshuaiaTierra del FuegoArgentina.

Background:Conceptual clarity is important to attain precise communication of scientific knowledge and to implement appropriate technological and policy *** concepts referring to forest management are widely used by decision-makers,regardless of their *** the scientific and methodological issues of forestry practices are frequently discussed in the literature,their normative dimensions are rarely ***,linguistic uncertainty increases when different environmentally ethical perspectives and ways of valuing forests are *** objective was to compare different conceptualizations on the silvicultural systems suggested for forest management and the implications they have for *** have conceptually contrasted highintensity forestry practices with variable retention harvesting,considering different environmentally ethical perspectives and forest valuation ***:Clear boundaries between clear-cutting,selective logging,and variable retention harvesting can be evidenced when different ethical points of view and alternatives in the human-nature relationships are *** have found a variety of definitions of variable retention harvesting that can be analyzed under different ethical *** contrasting views on variable retention harvesting can be evidenced if nature is considered to be purely at human’s service or if it is conceptualized as humans co-inhabiting with *** latter position implies that the maintenance of ecological,evolutionary,and historical processes supported by unmanaged forest stands is a crucial step for forest management proposals based on variable retention ***:Forestry practices that are focused on forest yields and that misinterpret functional uncertainty of forest functioning would be ***,forestry with variable retention harvesting could imply good yields with reasonable conservation management in some contexts,while it could be unacce

关键词： Environmental ethical perspectives Consequentialism Deontological ethics virtue ethics Policy options for forest and biocultural conservation

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sintering kinetics of Ni_2Fesb powder alloys produced by mechanical milling

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Transactions of Nonferrous Metals society of China 2016年第8期26卷 2126-2135页

作者： F.ALvARADO-HERNáNDEZ O.jim.nez G.GONZALEZ-CAsTANEDA v.BALTAZAR-HERNáNDEZ J.CABEZAs-vILLA M.ALBITER H.vERGARA-HERNáNDEZ L.OLMOs Unidad Académica de Ingeniería I Universidad Autónoma de ZacatecasJardín Juárez 147 Centro Histórico Zacatecas Zacatecas C. P. 98000 México Departamento de Ingeniería de Proyectos CUCEI Universidad de GuadalajaraBlvd. Marcelino García Barragán 1421 Olímpica Guadalajara Jalisco C. P. 44430 Mexico INICIT Universidad Michoacana de San Nicolás de HidalgoFco. J. Mujica S/N C.U. Morelia Michoacán C. P. 58060 México División de Estudios de Posgrado e Investigación TecNM/Instituto Tecnológico de MoreliaAv. Tecnológico # 1500 Colonia Lomas de Santiaguito Morelia Michoacán C. P. 58120 México

A ternary Ni2Fesb shape memory alloy was fabricated by powder metallurgy route. sintering kinetics was estimated from dilatometry tests; whereas the microstructure and morphology of the powder and consolidated bulk samples were evaluated by XRD and sEM, respectively. Microhardness tests were performed on the surface of sintered samples. The results indicated that milling time has an effect on the shape and particle size as well as the homogeneity of the crystalline structures of the powders. samples with longer milling time presented higher relative densities, better distribution of the elements on the alloy as well as the L21 and martensite phases, which will give the shape memory effect. The estimated activation energy values ranged from 109 to 282 kJ/mol at temperatures between 750 and 1273 K, indicating that sintering is controlled mainly by volume diffusion. Microhardness was improved by increasing the milling time and the heating rate.

关键词： Ni-based shape memory alloy mechanical milling solid state sintering microhardness

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Model based current mode control design and experimental validation for a 3φ rectifier under unbalanced grid voltage conditions

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Journal of Modern Power systems and Clean Energy 2018年第4期6卷 777-790页

作者： P.R.MARTínez-RODRIGEZ Jose M.sOsA samuel ITURRIAGA-MEDINA Gerardo EsCOBAR Gerardo váZQUEZ-GUZMáN Andres A.vALDEZ-FERNáNDEZ school of sciencies UASLP Laboratory of Electrical and Power Electronics ITESI school of Engineering Universidad Modelo

This paper addresses the control design and the experimental validation of a current mode control for a three phase voltage source rectifier. The proposed control law is able to fulfill the voltage regulation and the current tracking control objectives despite of unbalanced and distorted grid voltages. The proposed control law consists of two loops, which are referred as inner tracking loop and the outer voltage regulation loop. The inner loop is designed to provide damping to the system, which also includes and adaptive mechanism. The construction of the current reference is based on the positive component detection of thegrid voltage. Therefore, the current produced by the power rectifier is proportional to the fundamental component of the grid voltage, despite of the presence of unbalanced grid voltages. The voltage regulation loop is designed as a proportional-integral controller, which is aimed to regulate the DC output voltage to a desired level. Finally, experimental results are obtained in an experimental prototype of2 kW to evaluate the performance of the proposed controller.

关键词： Pulse-width modulation rectifier Power factor correction Positive-component Current mode control

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Induced Dipoles in Electromagnetic Media in Motion

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Journal of Electromagnetic Analysis and Applications 2018年第11期10卷 185-192页

作者： José-Antonio-Eduardo Roa-Neri José-Luis jim.nez-Ramírez Ignacio Campos-Flores área de Física Teórica y Materia Condensada División de Ciencias Básicas e Ingeniería Universidad Autónoma Metropolitana Unidad Azcapotzalco México D. F. México Departamento de Física Facultad de Ciencias Universidad Nacional Autónoma de México México D. F. México

We present a non-relativistic approach to the equivalent polarization Peq=(1/c2)v×Meq, that appears in a magnetized medium in motion. We apply an analogous method to that used by Panofsky and Phillips to calculate the symmetric effect, the equivalent magnetization that appears in a polarized dielectric in motion, Meq=P×v,?This method is based on a particular expression of Maxwell’s equations and the application of the convective derivative. These authors argue, however, that the equivalent polarization can be obtained only with a relativistic approach. We show that with the same method, but with a different and equivalent expression of Maxwell’s equations, this effect can also be calculated. In this way both effects can be considered relativistic effects to first order in v/c.

关键词： Moving Media Polarized Dielectric Macroscopic Maxwell Equations Induction of Magnetic Dipoles

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Optical clearing mechanisms characterization in muscle

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Journal of Innovative Optical Health sciences 2016年第5期9卷 82-100页

作者： Luís Oliveira M.Inês Carvalho Elisabete Nogueira valery v.Tuchin Physics Department–Polytechnic Institute of Porto school of Engineering Rua Dr.Antonio Bernardino de Almeida 4314200-072 PortoPortugal FEUP–University of Porto Rua Dr.Roberto Frias 4200-465 PortoPortugal CIETI–Centre of Innovation in Engineering and Industrial Technology ISEP Rua Dr.Antonio Bernardino de Almeida4314200-072 PortoPortugal DEEC/FEUP and INEsC TEC University of Porto Rua Dr.Roberto Frias 4200-465 PortoPortugal Research-Education Institute of Optics and Biophotonics saratov National Research state University 83 Astrakhanskaya street Saratov 410012Russia Laboratory of Laser Diagnostics of Technical and Living systems Institute of Precision Mechanics and Control ras 24 Rabochaya street Saratov 410028Russia Interdisciplinary Laboratory of Biophotonics Tomsk National Research state University 36 Lenin's avenue Tomsk 634050Russia

Optical immersion clearing is a technique that has been widely studied for more than two decades and that is used to originate a temporary transparency effect in biological *** applied in cooperation with clinical methods it provides optimization of diagnosis and treatment *** technique turns biological tissues more transparent through two main mechanisms-tissue dehydration and refractive index(RI)matching between tissue *** matching is obtained by partial replacement of interstit ial water by a biocompat ible agent that presents higher RI and it can be completely rever sible by natural rehydration in vrivo or by assisted rehydration in ex vivo *** data to characterize and discriminate between the two mechanisms and to find new ones are *** a simple method,based on collimated transmittance and thickness measurements made from muscle samples under treatment,we have estimated the diffusion properties of glucose,ethylene glycol(EG)and water that were used to perform such char acterization and *** these properties with data from literature that characterize their diffusion in water we have observed that musde cell membrane permeability limits agent and water diffusion in the *** same experi-mental data has allowed to calculate the optical dearing(OC)eficiency and make an inter-pretation of the internal changes that occurred in muscle during the *** same methodology can now be used to perform similar studies with other agents and in other tissues in order to solve engineering problems at design of inexpensive and robust technologies for a *** improvement of optical tomogr aphic techmiques with better contrast and in depth imaging.

关键词： Collimated transmittance agent diffusivity tissue dehydration thickness variation refractive index matching glucose ethylene glycol

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Heat transfer in a tapered fluidized bed of biomass particles with pulsed gas flow

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Particuology 2019年第1期17卷 2-14页

作者： Dening Jia Xiaotao Bi C. jim Lim shahab sokhansanj Atsushi Tsutsumi Department of Chemical and Biological Engineering The University of British Columbia2360 East MallVancouverBCV6T 1Z3Canada Environmental sciences Division Oak Ridge National LaboratoryOak RidgeTN 37831USA Collaborative Research Center for Energy Engineering Institute of Industrial ScienceThe University of Tokyo4-6-1 KomabaMeguro-kuTokyo 153-8505Japan

Bed-to-surface heat transfer of pure biomass particles in a pulsed fluidized bed with a tapered bottom section was investigated. Three biomass species — Douglas fir, pine, and switchgrass — were studied under various operating conditions. Their heat transfer coefficients were found to be closely associated with hydrodynamics dominated by gas pulsations. A higher superficial gas velocity generally yielded better gas–solid contact and higher heat transfer rates. A moderately increasing pulsation frequency promoted convective heat transfer of particles but also reduced pulsation intensity, leading to undesired flow behaviours such as channelling and partial defluidization. The study of the pulsation duty cycle revealed that, for cohesive particles, a smaller duty cycle was preferred to generate powerful pulsations to break up inter-particle forces. Moreover, a duty cycle increase allowed higher gas throughput as long as a suitable fluidization was maintained. The addition of finer particles to a coarse fraction increased particle mobility, and subsequently heat transfer, which also explained the higher heat transfer coefficients of switchgrass as it contained more fines compared with fir and pine. Experimental results in the tapered bed were also compared with those of non-tapered geometry where a 10%–20% increase in heat transfer was observed.

关键词： Fluidized bed Gas pulsations Tapered column Heat transfer Biomass

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African Dust storms Reaching Puerto Rican Coast stimulate the secretion of IL-6 and IL-8 and Cause Cytotoxicity to Human Bronchial Epithelial Cells (BEAs-2B)

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Health 2013年第10期5卷 14-28页

作者： Rosa I. Rodríguez-Cotto Mario G. Ortiz-Martínez Evasomary Rivera-Ramírez Loyda B. Méndez Julio C. Dávila Braulio D. jim.nez-vélez Department of Biochemistry University of Puerto Rico-Medical Sciences Campus San Juan Puerto Rico Center for Environmental and Toxicological Research San Juan Puerto Rico Department of Biochemistry University of Puerto Rico-Medical Sciences Campus San Juan Puerto Rico Center for Environmental and Toxicological Research San Juan Puerto Rico Science and Technology School Eastern University Carolina Puerto Rico Department of Biochemistry University of Puerto Rico-Medical Sciences Campus San Juan Puerto Rico Center for Environmental and Toxicological Research San Juan Puerto Rico

African dust storm events (ADE) travel across theAtlantic Ocean(ADEAO) and reach the Puerto Rican coast (ADEPRC), potentially impacting air quality and human health. To what extent seasonal variations in atmospheric particulate matter (PM) size fractions, composition and sources trigger respiratory-adverse effects to Puerto Ricans is still unclear. In the present study, we investigated the pro-inflammatory and cytotoxic effects of PM samples harvested during ADEAO (PM10), ADEPRC (PM2.5 and PM10) and Non-ADE (Pre-and Post-ADEAO and Non-ADEPRC), using BEAs-2B cells. Endotoxins (ENX) in PM2.5 and PM10 extracts and traces of metals (TMET) in PM2.5 extracts were also examined. IL-6 and IL-8 secretion and cytotoxicity were used as endpoints. ADEAO and ADEPRC extracts were found to be more cytotoxic than Non-ADE and ADEAO were more toxic than ADEPRC extracts. PM10 extracts from ADEAO and Post-ADEAO caused significant secretion of IL-8. IL-6 and IL-8 secretion was higher following treatment with PM10 and PM2.5 ADEPRC than with Non-ADEPRC extracts. ENX levels were found to be higher in PM10 ADEAO than in the rest of the samples tested. TMET levels were higher in PM2.5 ADEPRC than in Non-ADEPRC extracts. Deferoxamine significantly reduced cytotoxicity and IL-6 and IL-8 secretion whereas Polymyxin B did not. TMET in PM2.5 fractions is a major determinant in ADEPRC-induced toxicity and work in conjunction with ENX to cause toxicity to lung cells in vitro. ENX and TMET may be responsible, in part, for triggering PM-respiratory adverse responses in susceptible and predisposed individuals.

关键词： Dust storm Particulate Matter Endotoxins Metals BEAs-2B Cells

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