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Dendritic Growth, Eutectic Features and Their Effects on Hardness of a Ternary Sn–Zn–Cu Solder Alloy

Acta Metallurgica Sinica(English Letters) 2017年第6期30卷 528-540页

作者： Bismarck Luiz Silva rodrigo Valenzuela Reyes Amauri Garcia JoséEduardo Spinelli Department of Materials Engineering Federal University of Rio Grande do Norte-UFRNNatalRN 59078-970Brazil Department of Materials Engineering Federal University of Sao Carlos-UFSCarSao CarlosSP 13565-905Brazil Department of Manufacturing and Materials Engineering University of CampinasUNICAMPCampinasSP 13083-860Brazil

The present investigation is based on the results of a directionally solidified （DS） Sn-9 wt%Zn-2 wt%Cu alloy, including primary/secondary/tertiary dendrite arm spacings of the Sn-rich matrix, the morphologies of the eutectic mixture and the corresponding interphase spacing, the nature and proportion of the Cu-Zn intermetallic compound （IMC）. The main purpose is to establish interrelations of these microstructure features with experimental solidification thermal parameters, such as cooling rates and growth rates （v）, macrosegregation and hardness. Such interrelations are interesting for both industry and academy since they represent a tool permitting the preprogramming of final properties based on the design of the microstructure. In the case of Sn-Zn-Cu alloys, hardly anything is known about the combined effects of the length scale of the microstructure and fraction and distribution of the primary IMC on hardness. The alloy microstructure is composed of a β-Sn dendritic region, surrounded by a eutectic mixture of α-Zn and β-Sn phases and the γ-Cu5Zn8 IMC. The eutectic interphase spacing varies in the range 1.2-3.6 μm, with the α-Zn phase having a globular morphology for ν 〉 0.5 mm/s and a needle-like morphology for ν 〈 0.3 mm/s. A modified Hall-Petch-type experimental expression relating hardness to the interphase spacing is proposed.

关键词： Sn-Zn-Cu solder alloy Solidification Microstructure Eutectic morphology Hardness

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Modeling egg development of the pest Clavipalpus ursinus （Coleoptera： Melolonthidae） using a temperature-dependent approach

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Insect Science 2012年第6期19卷 657-665页

作者： Andrea Escobar rodrigo Gil Carlos Ricardo Bojaca Jaime Jimenez Facultad de Ciencias Naturales e Ingenieria Departamento de Ciencias Basicas Universidad de Bogota Jorge Tadeo Lozano Bogota Direccion Tecnica de Sanidad Vegetal Instituto Colombiano Agropecuario Bogota Colombia

Predicting the population dynamics of insects in natural conditions is es- sential for their management or preservation, and temperature-dependent development models contribute to achieving this. In this research the effects of temperature and soil moisture content on egg development and hatching of Clavipalpus ursinus （Blanchard） were evaluated. The eggs were exposed to seven temperature treatments with averages of 7.2, 13.0, 15.5, 19.7, 20.6, 22.0 and 25.3~C, in combination with three soil moisture contents of 40%, 60% and 80%. A linear and two non-linear （Lactin and Briere） models were evaluated in order to determine the thermal requirements of this developmental stage. Temperature affected significantly the time of development and egg hatching, while no significant effect was observed for moisture content. Thermal requirements were set as： 7.2℃ for lower developmental threshold, 20.6℃ for optimum developmental threshold, 25.3℃ for maximum temperature and 344.83 degree-days for the thermal constant. The linear model described satisfactorily egg development at intermediate temperatures; nev- ertheless, a slightly better fit of the observed data was obtained with the Lactin model. Egg development took place inside a narrow range of temperatures. Consequently, an increment of soil temperature could generate a negative impact on the population size of this species or changes in its biological parameters.

关键词： egg development pests soil moisture thermal requirements

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Temporal dynamics of shallow subtidal meiobenthos from a beach in Tenerife (Canary Islands, northeast Atlantic Ocean)

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Acta Oceanologica Sinica 2013年第8期32卷 44-54页

作者： rodrigo Riera Jorge Núez María del Carmen Brito Centro de Investigaciones Medioambientales del Atlántico (CIMA SL) Arzobispo Elías Yanes 4438206 La Laguna Tenerife Canary Islands Spain Benthos Laboratory Department of Animal Biology Faculty of Biology University of La Laguna

A shallow subtidal （3 m deep） meiofaunal assemblage in Los Abrigos Bay, Tenerife, Canary Islands was sam- pled during May 2000-April 2001. The main aims were to （1） find temporal variations in meiofaunal assem- blage structure and overall abundance, as well as in the most abundant meiofaunal species throughout the study period, and （2） identify environmental variables （sedimentary composition, organic matter content, and total nitrogen） that better explain meiofaunal assemblage structure during the study year. The most abundant species were the nematodes Siphonolaimus sp. 2 and Catanema sp., which represented 46.2% of the overall meiofaunal abundances and varied significantly throughout the study duration. Overall meio- faunal abundance and the most abundant taxonomic groups （nematodes, copepods, and oligochaetes） showed significant temporal variations during the study period. Nematodes overwhelmingly dominated during the study period, ranging from 78% in May to 97.34% in February. Multivariate analyses showed seasonality in meiofaunal community structure during the study year, with the lowest abundances in May. Keywords： Meiofauna, assemblage structure, subtidal, Canary Islands, Atlantic Ocean

关键词： Meiofauna assemblage structure subtidal Canary Islands Atlantic Ocean

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Single-molecule DNA sequencing using two-dimensionalTi2C(OH)2 MXene nanopores: A first-principles investigation

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Nano Research 2022年第11期15卷 9843-9849页

作者： Jariyanee Prasongkit Sirichok Jungthawan rodrigo G.Amorim Ralph H.Scheicher Division of Physics Faculty of ScienceNakhon Phanom UniversityNakhon Phanom 48000Thailand School of Physics Institute of ScienceSuranaree University of Technology111 University AveNakhon Ratchasima 30000Thailand Center of Excellence in Advanced Functional Materials Suranaree University of TechnologyNakhon Ratchasima 30000Thailand Thailand Center of Excellence in Physics Ministry of Higher EducationScienceResearch and Innovation328 Si Ayutthaya RoadBangkok 10400Thailand Departamento de Física ICExUniversidade Federal Fluminense-UFFVolta Redonda/RJ 27213-145Brazil Division of Materials Theory Department of Physics and AstronomyUppsala UniversityUppsala SE-75120Sweden

Nanopore-based devices have provided exciting opportunities to develop affordable label-free DNA sequencing *** a decade ago,graphene has been proposed as a two-dimensional(2D)nanopore membrane in order to achieve single-base ***,it was experimentally revealed that clogging of the graphene nanopore can occur due to the hydrophobic nature of graphene,thus hindering the translocation of *** overcome this problem,the exploration of alternative 2D materials has gained considerable interest over the last *** we show that a Ti_(2)C-based MXene nanopore functionalized by hydroxyl groups(–OH)exhibits transverse conductance properties that allow for the distinction between all four naturally occurring DNA *** have used a combination of density functional theory and non-equilibrium Green’s function method to sample over multiple orientations of the nucleotides in the nanopore,as generated from molecular dynamics *** conductance variation resulting from sweeping an applied gate voltage demonstrates that the Ti_(2)C-based MXene nanopore possesses high potential to rapidly and reliably sequence *** findings open the door to further theoretical and experimental explorations of MXene nanopores as a promising 2D material for nanopore-based DNA sensing.

关键词： nanopore DNA sequencing MXenes first-principles quantum transport

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Bitcoin pricing: impact of attractiveness variables

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Financial Innovation 2020年第1期6卷 373-391页

作者： rodrigo Hakim das Neves Sao Paulo School Of Economics(FGV) Sao PauloBrazil

The research seeks to contribute to Bitcoin pricing analysis based on the dynamics between variables of attractiveness and the value of the digital *** the error correction model,the relationship between the price of the virtual currency,Bitcoin,and the number of Google searches that used the terms bitcoin,bitcoin crash and crisis between December 2012 and February 2018 is *** study also applied the same analysis to prices of Bitcoin denominated in different sovereign currencies traded during the same *** Johansen(J Econ Dyn Control 12:231-254,1988)test demonstrates that the price and number of searches on Google for the first two terms are *** research indicates that there are strong short-term and long-term dynamics among attractiveness factors,suggesting that an increase in worldwide interest in Bitcoin is usually preceded by a price *** contrast,an increase in market mistrust over a collapse of the currency,as measured by the term bitcoin crash,is followed by a fall in *** world economic crisis events appear to have a strong impact on interest in the virtual *** study demonstrates that during a worldwide crisis Bitcoin becomes an alternative investment,increasing its *** on it,bitcoin may be used as a safe haven by the financial market and its intrinsic characteristics might help the investors and governments to find new mechanisms to deal with monetary transactions.

关键词： Bitcoin pricing Price variables Crisis

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Thermoregulatory function and sexual dimorphism of the throat sack in Helmeted Guineafowl(Numida meleagris)across Africa

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Avian Research 2022年第3期13卷 239-248页

作者： Johann H.Van Niekerk rodrigo Megía-Palma Giovanni Forcina Department of Environmental Sciences College of Agriculture and Environmental SciencesUniversity of South AfricaP.O.Box 392Pretoria0003South Africa Universidad de Alcal a(UAH) Department of Biomedicine and BiotechnologySchool of PharmacyA-2 Highwaykm 33.60028805Alcal a de HenaresMadridSpain Universidad de Alcal a(UAH) Global Change Ecology and Evolution Research Group(GloCEE)Departamento de Ciencias de la Vida28805Alcal a de HenaresMadridSpain CIBIO Centro de Investigaç~ao em Biodiversidade e Recursos Gen eticosInBIO Laborat orio AssociadoCampus de Vair~aoUniversidade do Porto4485-661Vair~aoPortugal BIOPOLIS Program in Genomics Biodiversity and Land PlanningCIBIOCampus de Vair~ao4485-661Vair~aoPortugal

The responses of ground-dwelling birds to heat and cold stress encompass a variety of behavioural,physiological and even morphological ***,the role of glabrous skin in this respect has been marginally addressed so *** Helmeted Guineafowl(Numida meleagris)is a landfowl distributed across Sub-Saharan Africa with eight traditionally recognised extant *** the most prominent morphological traits underlying intraspecific variability are size and pigmentation of the bare throat skin(or sack),which might be related to the different habitats and environmental conditions across its wide *** order to explore the Helmeted Guineafowl range-wide sack variation and pigmentation in relation to thermoregulation and sexual signalling,we collected morphometric and environmental information for *** integrating field data with the inspection of photographic material encompassing seven subspecies and environmental information from their *** data evidenced that sack size was significantly correlated with ambient temperature,thus pointing to a likely involvement of the throat sack in *** the pictorial data from all subspecies were pooled,sack size correlated negatively with biomass,rainfall and humidity,while a positive correlation was found with annual solar *** size correlated positively with monthly temperature variation among the bluethroated subspecies from southern Africa as opposed to the black-throated subspecies ranging north to Zambia and ***,in this latter group the sack was often larger during winter months,possibly to maximise solar radiation ***,sack size was related to sex dimorphism in two *** morphology and colour in the Helmeted Guineafowl likely modulate body temperature by evaporative cooling or heating upon needs,but in some subspecies it is also seemingly related to sexual *** studies are needed to fully understand the mu

关键词： Evaporative cooling Helmeted guineafowl Sexual size dimorphism Sub-Saharan Africa Thermoregulation Throat sack

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Identifiability and Stability of an Inverse Problem Involving a Fredholm Equation

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Chinese Annals of Mathematics,Series B 2015年第5期36卷 737-762页

作者： Carlos CONCA rodrigo LECAROS Jaime H.ORTEGA Lionel ROSIER Centro de Modelamiento Matematico and Departamento de Ingenier?a Matematica Universidad de Chile (UMI CNRS 2807) Avda Beauchef 851 Edificio Norte Casilla 170-3 Correo 3 Santiago 8370459Chile Centre Automatique et Systemes MINES Paris Tech PSL Research University

The authors study a linear inverse problem with a biological interpretation,which is modelled by a Fredholm integral equation of the first kind, where the kernel is represented by step functions. Based on different as... 详细信息

关键词： Inverse problems Olfactory system Kernel determination Fredholm integral equation Partial differential equations Numerical reconstruction

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Availability-based simulation and optimization modeling framework for open-pit mine truck allocation under dynamic constraints

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International Journal of Mining Science and Technology 2013年第1期23卷 113-119页

作者： Mena rodrigo Zio Enrico Kristjanpoller Fredy Arata Adolfo European Foundation for New Energy-Electricity of France at Central School of Paris-Supelec Paris 92295 France Energy Department Polytechnic of Milan Milan 20133 Italy Department of Industrial Engineering Federico Santa Maria Technical University Valparaiso 2390123 Chile Industrial Engineering School Pontifical Catholic University of Valparaiso Valparaiso 2340025 Chile

We present a novel system productivity simulation and optimization modeling framework in which equipment availability is a variable in the expected productivity function of the system. The framework is used for allocating trucks by route according to their operating performances in a truck-shovel system of an open-pit mine, so as to maximize the overall productivity of the fleet. We implement the framework in an originally designed and specifically developed simulator-optimizer software tool. We make an application on a real open-pit mine case study taking into account the stochasticity of the equipment behavior and environment. The total system production values obtained with and without considering the equipment reliability, availability and maintainability (RAM) characteristics are compared. We show that by taking into account the truck and shovel RAM aspects, we can maximize the total production of the system and obtain specific information on the production availability and productivity of its components.

关键词： Simulation Optimization Reliability Productivity Open-pit Truck allocation

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ON THE VALIDITY OF THE LOCAL FOURIER ANALYSIS

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Journal of Computational Mathematics 2019年第3期37卷 340-348页

作者： Carmen rodrigo Francisco J.Gaspar Ludmil T.Zikatanov Departamento de Matematica Aplicada IUMAUniversidad de ZaragozaZaragozaSpain CWI Centrum Wiskunde & InformaticaScience Park 1231090 AmsterdamThe Netherlands Department of Mathematics The Pennsylvania State UniversityUniversity ParkPennsylvania 16802USAInstitute for Mathematics and InformaticsBulgarian Academy of SciencesSofia.Bulgaria

Local Fourier analysis(LFA)is a useful tool in predicting the convergence factors of geometric multigrid methods(GMG).As is well known,on rectangular domains with periodic boundary conditions this analysis gives the exact convergence factors of such met *** other boundary conditions are considered,however,this analysis was judged as been heuristic,with limited capabilities in predicting multigrid convergence *** this work,using the Fourier method,we extend these results by proving that such analysis yields the exact convergence factors for a wider class of problems,some of which can not be handled by the traditional rigorous Fourier analysis.

关键词： Local Fourier analysis Multigrid Fourier method

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Catalytic combustion of soot over ceria-zinc mixed oxides catalysts supported onto cordierite

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Journal of Environmental Sciences 2014年第3期26卷 694-701页

作者： Leandro Fontanetti Nascimento Renata Figueredo Martins rodrigo Ferreira Silva Osvaldo Antonio Serra Department of Chemistry FFCLRP University of Sao Paulo

Modified substrates as outer heterogeneous catalysts was employed to reduce the soot generated from incomplete combustion of diesel or diesel/biodiesel blends, a process that harms the environment and public health. The unique storage properties of ceria （CeO2） makes it one of the most efficient catalysts available to date. Here, we proposed that ceria-based catalysts can lower the temperature at which soot combustion occurs; more specifically, from 610℃ to values included in the diesel exhausts operation range （300-450℃）. The sol-gel method was used to synthesize mixed oxide-based catalysts （CeO2：ZnO）; the resulting catalysts were deposited onto cordierite substrates. In addition, the morphological and structural properties of the material were evaluated by XRD, BET, TPR-H2, and SEM. Thermogravimetric （TG/DTA） analysis revealed that the presence of the catalyst decreased the soot combustion temperature by 200℃ on average, indicating that the oxygen species arise at low temperatures in this situation, promoting highly reactive oxidation reactions. Comparative analysis of soot emission by diffuse reflectance spectroscopy （DRS） showed that catalyst-impregnated cordierite samples efficiently oxidized soot in a diesel/biodiesel stationary motor： soot emission decreased by more than 70%.

关键词： soot oxidation mixed oxides ceria

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