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Experimental investigation of flow field in a laboratory-scale compressor

Chinese Journal of Aeronautics 2017年第1期30卷 31-46页

作者： Ma Hongwei Wei Wei xavier Ottavy Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics School of Energy and Power Engineering Beihang University Beijing 100083 China Collaborative Innovation Center of Advanced Aero-Engine Beijing 100083 China China Academy of Aerospace Aerodynamics (CAAA) Yungangxi Rd. Fengtai Dist. Beijing 100074 China Laboratoire de Mecanique des Fluides et d'Acoustique (LMFA) Groupe TurbomachinesEcole Centrale de Lyon 36 av. Guy de Collongue 69134 Ecully cedex France

The inner flow environment of turbomachinery presents strong three-dimensional, rotational, and unsteady characteristics. Consequently, a deep understanding of these flow phenomena will be the prerequisite to establish a state-of-the-art design system of turbomachinery. Currently the development of more accurate turbulence models and CFD tools is in urgent need for a high-quality database for validation, especially the advanced CFD tools, such as large eddy simulation（LES）. Under this circumstance, this paper presents a detailed experimental investigation on the 3D unsteady flow field inside a laboratory-scale isolated-rotor with multiple advanced measurement techniques, including traditional aerodynamic probes, hotwire probes, unsteady endwall static pressure measurement, and stereo particle image velocimetry（SPIV）. The inlet boundary layer profile is measured with both hotwire probe and aerodynamic probe. The steady and unsteady flow fields at the outlet of the rotor are measured with a mini five-hole probe and a single-slanted hotwire probe. The instantaneous flow field in the rotor tip region inside the passage is captured with SPIV,and then a statistical analysis of the spatial distribution of the instantaneous tip leakage vortex/flow is performed to understand its dynamic characteristics. Besides these, the uncertainty analysis of each measurement technique is described. This database is quite sufficient to validate the advanced numerical simulation with LES. The identification process of the tip leakage vortex core in the instantaneous frames obtained from SPIV is performed deliberately. It is concluded that the ensemble-averaged flow field could not represent the tip leakage vortex strength and the trajectory trace. The development of the tip leakage vortex could be clearly cataloged into three phasesaccording to their statistical spatial distribution. The streamwise velocity loss induced by the tip leakage flow increases until the splitting process is weak

关键词： Database Laboratory-scale compres-sor SPIV Tip leakage flow Tip leakage vortex

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Vigilance behavior of Pyrenean chamois Rupicapra pyrenaica pyrenaica:Effect of sex and position in the herd

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Current Zoology 2010年第2期56卷 232-237页

作者： Antoni DALMAU Alfred FERRET xavier MANTECA Irta Finca Camps i Armet s/n Monells Universitat Autònoma de Barcelona School of Veterinary Science Departament de Ciència Animal i dels Aliments

The Pyrenean chamois Rupicapra pyrenaica pyrenaica is a mountain-dwelling ungulate with an extensive presence in open areas. Optimal group size results from the trade off between advantages （a reduction in the risk of predation） and disadvantages （competition between members of the herd） of group living. In addition, advantages and disadvantages of group living may vary depending on the position of each individual within the herd. Our objective was to study the effect of central vs. peripheral position in the herd on feeding and vigilance behavior in male and female Pyrenean chamois and to ascertain if a group size effect existed. We used focal animal sampling and recorded social interactions when a focal animal was involved. With males, vigilance rate was higher in the central part of the group than at the periphery, probably due to a higher density of animals in the central part of the herd and a higher probability of being disturbed by conspecifics. With females, vigilance rate did not differ according to position in the herd. Females spent more time feeding than males, and males showed a higher frequency of the vigilance behavior than females. We did not observe a clear relationship between group size and vigilance behavior. The differences in vigilance behavior might be due to social interactions

关键词： Antagonistic interactions Group size Position Pyrenean chamois Sex Vigilance

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Hydrolysis of Urea to Produce Ammonia Dircio Francisco xavier Fatima Ximenes

Hydrolysis of Urea to Produce Ammonia Dircio Francisco Xavie...

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作者： Dircio Francisco xavier Fatima Ximenes（弗朗西斯科）华东理工大学

学位级别：硕士

氮氧化物（NOx）引起了巨大的环境问题,是目前世界上最大的环境污染物之一,随着对NOx法规的逐步收紧,世界各国都在积极开展减少NOx污染的研究。目前已开发利用了多种技术,其中选择性催化还原（SCR）和选择性非催化还原（SNCR）具有较高... 详细信息

氮氧化物（NOx）引起了巨大的环境问题,是目前世界上最大的环境污染物之一,随着对NOx法规的逐步收紧,世界各国都在积极开展减少NOx污染的研究。目前已开发利用了多种技术,其中选择性催化还原（SCR）和选择性非催化还原（SNCR）具有较高的脱硝效率。在SCR和SNCR工艺中,还原剂被注入烟气中,将NOx还原为无害氮（N2）。目前最常用的还原剂是氨（NH3）。尿素催化水解制氨在氨基脱氮过程中起着重要作用。本论文的目标有三个。首先,对尿素水解的催化剂进行筛选,其中均相催化剂表现出了良好的性能,因此本文用选择该类催化剂来进行尿素催化水解反应,然后尿素水解的转化率采用滴定法来进行分析。第二是设计了四因素,三水平Box-Behnken实验,结合响应面法对工艺条件进行优化,研究反应温度,反应时间,反应压力和催化剂用量对尿素水解制氨的影响及其交互作用。建立了尿素水解率的相关模型。第三是采用物料平衡方程,热量平衡方程,化学平衡方程及相平衡方程组成的非线性方程组来构建开口体系内尿素水解过程的热力学模型和动力学模型,并引入修正的Lewis-Randall方程和修正的Herry方程来描述水解反应器内NH3-CO2-H2O-（NH2）2CO（ACWU）四元多自由度气液平衡关系,气液两相的非理想性则分解采用PR状态方程和扩展UNIQUAC模型进行修正。结果表明,采用催化活性较好的乙酸钠（7g）催化剂对工艺条件进行优化,响应面法最优化的合成条件为;反应温度160℃,反应时间4h,反应压力0.4MPa和催化剂用量0.034wt%,在此工艺条件下尿素水解的转化率为98.620%,同时建立了尿素水解制氨的二次数学模型,该模型对实验结果有良好的预测作用。

关键词：尿素水解制氨热力学动力学

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Ionic thermoelectric materials and devices

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Journal of Energy Chemistry 2021年第10期30卷 88-103,I0003页

作者： Dan Zhao Alois Würger xavier Crispin Laboratory of Organic Electronics Linkoping UniversityNorrkoping 60247Sweden Univ.Bordeaux&CNRS LOMA(UMR 5798)F-33405 TalenceFrance Wallenberg Wood Science Center ITNLinköping UniversityNorrköpingSweden

The tremendous amount of wasted heat from solar radiation and industry dissipation has motivated the development of thermoelectric concepts that directly convert heat into *** main challenge in practical applications for thermoelectrics is the high cost from both materials and ***,breakthrough progresses in ionic thermoelectrics open up new possibilities to charge energy storage devices when submitted to a temperature *** charging voltage is internally from the ionic Seebeck effect of the electrolyte between two *** electrolytes with high thermoelectric figure of merit are classified as ionic thermoelectric *** ionic thermoelectric materials are composed of abundant elements,and they can generate hundreds of times larger thermal voltage than that of electronic *** emerging thermoelectric category brings new hope to fabricate low cost and large area heat-to-energy conversion devices,and triggers a renewed interest for ionic *** this review,we summarize the state of the art in the new field of ionic thermoelectrics,from the driving force of the ionic thermodiffusion to material and application *** present a general map of ionic thermoelectric materials,discuss the unique characters of each type of the reported electrolytes,and propose potential optimization and future topics of ionic thermoelectrics.

关键词： Electrolytes Soret effect Thermodiffusion Thermal energy conversion

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Selective and taxon-dependent effects of semi-feral cattle grazing on tree regeneration in an old-growth Mediterranean mountain forest

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Forest Ecosystems 2020年第1期7卷 128-140页

作者： xavier Fortuny Christopher Carcaillet Sandrine Chauchard Ecole Pratique des Hautes Etudes(EPHE) PSL University75014 ParisFrance Laboratoire d’ cologie des Hydrosystèmes Naturels et Anthropisés(UMR5023 CNRS UniversitéLyon 1ENTPE)69622 VilleurbanneFrance Universitéde Lorraine AgroParisTechINRAEUMR Silva54000 NancyFrance

Background:In Mediterranean mountain socio-ecosystems,both grazing by livestock and the dry season may influence tree ***,the relative contributions of these drivers are poorly known,even though present and future canopy composition might result from past and present variations in climate and herbivore *** study aims to test how semi-feral cattle presence and season affect tree ***:The study was conducted using permanent plots inside and outside a cattle exclosure in an old-growth Mediterranean *** and seedlings were counted five times per year(winter,early spring,middle spring,summer,fall)and monitored over 7 ***:Semi-feral cattle exclusion increased Acer,Fagus,Ilex,Pinus,Prunus and Quercus sapling densities and increased Acer,Fraxinus,Ilex,Quercus and Sorbus seedling ***,the dry season did not exert any noticeable effects on the sapling or seedling densities of any of the studied ***:Semi-feral cattle presence may limit tree regeneration through taxon-dependent effects,which suggests that the current decrease in grazing livestock across the Mediterranean basin will modify recruitment processes and,likely,future forest ***:Semi-feral cattle presence acts as a selective driver of tree community composition.

关键词： Cattle Climate Experiment Herbivory Forest pastoralism

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Effect of pre-and post-wildfire management practices on plant recovery after a wildfire in Northeast Iberian Peninsula

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Journal of Forestry Research 2020年第5期31卷 1647-1661页

作者： Marcos Francos Paulo Pereira xavier Ubeda GRAM(Grup de Recerca Ambiental Mediterrania) Department of GeographyUniversity of BarcelonaMontalegre608001 BarcelonaSpain Environmental Management Centre Mykolas Romeris UniversityVilniusLithuania

Fire and pre-or post-fire management practices shape the distribution and richness of plant ***,the effects of pre-and post-fire management on vegetation recovery were studied at different times,up to 18 months after a *** months after a 2015 wildfire,18 study plots were established(three 4-m^2 plots for each treatment),vegetation regrowth was monitored and vegetal species richness(S),evenness(IT),density(D),diversity(H0)and maximum diversity(HMax)after 2,10 and 18 *** treatments were(1)control,unaffected by 2015 wildfire;(2)no treatment(NT),burned in 2015 wildfire and not managed;(3)managed in 2005 and burned in 2015(M05B);(4)managed in 2015,2 months before wildfire(M15B);(5)cut and manual removal after the 2015 wildfire(CR);(6)cut and no trunk removal randomly deposited on topsoil after the 2015 wildfire(CL).All the treatments were carried out in a Pinus halepensis Miller *** 10 and 18 months after the wildfire,vegetation recovery was greater in NT,CR and CL plots than in M05B and M15B the *** 18 months after the wildfire,Brachypodium retusum(Pers.)*** Rosmarinus officinalis *** still dominant,especially in M15B,corroborating the belief that pre-fire treatment reduced ecosystem resilience and vegetal recovery compared to the NT and post-fire managed *** was significantly lower 10 months after wildfire in control plots,and IT was significantly higher in that inventory than previously in *** months after the wildfire,H0 was significantly lower in *** months post-wildfire,HMax was significantly lower in the control *** months after the wildfire,HMax,was significantly higher in CR,CL and M05B than in the control and M15B ***,pre-fire management was detrimental to post-fire vegetation recovery,while manual post-fire management proved beneficial.

关键词： Forest management Vegetation recovery Diversity Richness Evenness

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Long-term forest management after wildfire(Catalonia,NE Iberian Peninsula)

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Journal of Forestry Research 2020年第1期31卷 269-278页

作者： Marcos Francos xavier Ubeda Paulo Pereira GRAM(Grup de Recerca Ambiental Mediterrania) Department of GeographyUniversity of BarcelonaMontalegre608001 BarcelonaSpain Environmental Management Centre Mykolas Romeris UniversityVilniusLithuania

Studies of post-fire soil status in Mediterranean ecosystems are common;however,few have examined the effects of long-term forest management after a wildfire on physicochemical soil ***,we analyzed differences in soil properties attributable to long-term postfire management and assessed the sustainability of these management practices in relation to the soil *** study area is located in Odena in the northeast region of the Iberian Peninsula consisted of the control forest(burned more than 30 years ago),low density forest(LD;burned in a wildfire in 1986 and managed in 2005)and high density forest(HD;burned in a wildfire in 1986 and no managed).For soils from each plot,we measured soil water repellency,aggregate stability,total nitrogen(TN),soil organic matter(SOM),inorganic carbon(IC),pH,electrical conductivity,extractable calcium,magnesium,sodium,potassium(K),phosphorus,aluminum(Al),manganese(Mn),iron(Fe),zinc,copper,boron,chrome,silicon and sulfur and calculated the ratios of C/N,Ca+Mg/(Na+K)^1/2,Ca/Al and Ca/*** differences were found in TN,IC,SOM,pH,K,Al,Mn,Fe and C/N ratio(p<0.05).All soil properties were found to have largely recovered their pre-fire *** were affected by the post-fire management practices implemented 20 years after the fire,as reflected in their respective physicochemical properties,so that soil properties at the control and LD sites are more similar today than those at the control and HD ***,sustainable forest management can overcome soil degradation in areas affected by wildfire in the medium-and long-term by improving soil properties.

关键词： Soil chemical properties Aggregate stability Post-fire management Wildfire risk Vegetal density

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Understanding leukemic hematopoiesis as a complex adaptive system

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World Journal of Stem Cells 2015年第9期7卷 1145-1149页

作者： xavier Thomas Department of Hematology Lyon-Sud Hospital

Normal and abnormal hematopoiesis is working as a complex adaptive system. From this perspective, the development and the behavior of hematopoietic cell lineages appear as a balance between normal and abnormal hematopoiesis in the setting of a functioning or malfunctioning microenvironment under the control of the immune system and the influence of hereditary and environmental events.

关键词： Acute leukemia Complex adaptive system Stem cells

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Building the World Wide Hypermap(WWH)with a RESTful architecture

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International Journal of Digital Earth 2014年第3期7卷 175-193页

作者： Joan Maso xavier Pons Alaitz Zabala Center for Ecological Research and Forestry Applications(CREAF) Universitat Autònoma de BarcelonaBarcelonaSpain Department of Geography Universitat Autònoma de BarcelonaBarcelonaSpain

The hypermap concept was introduced in 1992 as a way to hyperlink geospatial features to text,multimedia or other geospatial *** then,the concept has been used in several applications,although it has been found to have some *** the other hand,Spatial Data Infrastructures(SDIs)adopt diverse and heterogeneous service oriented architectures(SOAs).They are developed by different standard bodies and are generally disconnected from mass market web *** work expands the hypermap concept to overcome its limitations and harmonise it with geospatial resource oriented architecture(ROA),connecting it to the semantic web and generalising it to the World Wide Hypermap(WWH)as a tool for building a single‘Digital Earth’.Global identifiers,dynamic links,link purposes and resource management capabilities are introduced as a solution that orchestrates data,metadata and data access services in a homogeneous *** is achieved by providing a set of rules using the current Internet paradigm formalised in the REpresentational State Transfer(REST)architecture and combining it with existing Open Geospatial Consortium(OGC)and International Organization for Standardization(ISO)standards.A reference implementation is also presented and the strategies needed to implement the WWH,which mainly consist in a set of additions to current Geographic Information System(GIS)products and a RESTful server that mediates between the Internet and the local GIS applications.

关键词： SDI URI standards hypermap RESTful

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A hot future for cool materials

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Frontiers in Energy 2023年第4期17卷 447-449页

作者： xavier MOYA Neil D.MATHUR Department of Materials Science University of CambridgeCambridge CB3 0FSUK

The ewidespreadneed to pump heat necessitates simprovements that will increase energy efficiency and,more generally,reduce eenvironmental *** discussed at the recent Calorics 2022 Conference,heat-pump devices based on... 详细信息

关键词： magnetocaloric electrocaloric mechanoca-loric elastocaloric barocaloric

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