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Application of fractal theory in assessing soil aggregates in Indian tropical ecosystems

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Journal of Forestry Research 2012年第3期23卷 355-364页

作者： S.k.Tripathi C.P.kushwaha S.k.basu Computer Science Department Banaras Hindu UniversityVaranasi-221005India Department of Forestry Mizoram UniversityAi-zawl-796009India Centre for Env.Sci.&Tech. Banaras Hindu UniversityVaranasi-221005India

Soil aggregation varies according to climatic and manage- ment factors, and is difficult to measure because of irregular shapes and sizes of soil aggregates. We applied fractal theory to assess soil aggrega- tion as affected by （1） land use change from forest to savanna, （2） nutri- ent additions in forest, ecotone, and savanna ecosystems, and （3） tillage practice and residue treatments in an agro-ecosystem. We used fractal dimensions nonlinear （D,o,-lin） and linear （Dlin） based on number of ag- gregates （N） and mass of aggregates （M）（the range of values were 2.6-2.89 and 2.694.41, respectively） to capture the variations in the sizes of soil aggregates due to land use and treatments/management in these ecosystems. The variation in the values of non-linear fractal dimension based on mass （DMnon-lin） was smaller in forest and savanna ecosystems with and without nutrient additions, while the variation was wider in agro-ecosystems with different management practices. Linear fractal dimensions based on number （Dr^i,） and mass （DMlin） of aggregates var- ied marginally in these ecosystems and did not capture the variations in soil aggregates well. The variations in non-linear fractal dimension indi- cate that continued nitrogen loading in forest accelerates the formation of macro-aggregates, whereas in savanna the situation was reversed. The values of non-linear fractal dimensions did not show significant change after 6 years of nutrient additions in the ecotone; reflecting a buffering mechanism of this system in soil aggregate formation. On the basis of non-linear fractal dimension values, we conclude that residue retention and minimum tillage are appropriate for proper maintenance of soil ag- gregate stability for sustained crop production in the Indian dry land agro-ecosystems

关键词： soil aggregates fractal tillage practice ecosystem Indian dry tropics

Effects of nano-voids and nano-cracks on the elastic properties of a host medium: xfem modeling with level-set function and free surface energy

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Acta Mechanica Sinica 2019年第4期35卷 799-811页

作者： b.E. Hachi D. Hachi M. Haboussi Laboratoire de Développement en Mécanique et Matériaux (LDMM) Université de Djelfa PB 3117 Djelfa Algérie Laboratoire d’Automatique Appliquée et Diagnostics Industriels (LAADI) Université de Djelfa PB 3117 Djelfa Algérie Laboratoire des Sciences des Procédés et des Matériaux (LSPM) Université Paris 13 UPR 3407 CNRS Paris France

This work deals with the influences of nano-heterogeneities in the form of voids/cavities or cracks on the elastic (please confirm which word is correct. effective or elastic? According to the title of paper, I choose elastic.) properties of a host medium. With a relatively large ratio of apparent-surface to volume and particularly strong physical interactions with the surrounding medium at nano-scale, nano-heterogeneities can potentially affect the elastic(effective or elastic?) properties of the parent medium (matrix) containing them in a significant manner. This has been reported by various theoretical and experimental studies, some of them are discussed in the present paper. To describe the positive (reinforcement) or negative (degradation) effect of the nano-heterogeneities from the modeling perspective, it is necessary to take into account the energy of interfaces/surfaces between nano-heterogeneities and the matrix which, by the fact of the relatively large extent of their apparent surface and their strong physical interaction with their neighborhood, can no longer be neglected compared to those of the volume energy. Thus, to account for the effects of interfaces/surfaces in a nanostructured heterogeneous medium, the coherent interface model is considered in the present investigation within a periodic homogenization procedure. In this interface/surface model, the displacement vector is assumed to be continuous across the interface while the stress vector is considered to be discontinuous and satisfying the Laplace-Young equations. To solve these equations coupled to the classical mechanical equilibrium problem, a numerical simulation tool is developed in a two-dimensional (2D) context using the eXtended Finite Element Method (XFEM) and the Level-Set functions. The developed numerical tool is then used to carry out a detailed analysis about the effect of nano-heterogeneities on the overall mechanical properties of a medium. The nano-heterogeneities are present

关键词： Interface/Surface energy XFEM Level-Set function Periodic homogenization Nano-voids/Nano-cavities Nano-cracks Nano-inclusions/Nano-heterogeneities

Coarsening kinetics of γ' Precipitates in Dendritic Regions of a Ni_3 Al base Alloy

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Journal of Materials Science & Technology 2012年第3期28卷 221-228页

作者： H.b.Motejadded M.Soltanieh S.Rastegari School of Metallurgy and Materials Engineering Iran University of Science and TechnologyTehranIran

Coarsening behavior of γ＇ precipitates in the dendritic regions of a Ni 3 Al base alloy containing chromium,molybdenum,zirconium and boron was *** treatment was performed up to 50 h at 900,1000 and 1100℃.The alloy was produced by vacuum-arc remelting *** show that coarsening of the γ＇ precipitates in this complex alloy containing high volume fractions of γ＇ phase follows Lifshitz-Slyozov-Wagner（LSW） *** activation energy of the γ＇ precipitates was evaluated to be about 253.5 ***-1 which shows that the growth phenomenon is controlled by volume diffusion of *** an innovative approach,diffusion coefficient of the solute element（s） and the interfacial energy between γ＇ precipitates and γ＇（matrix） were estimated at 900,1000 and 1100℃.Accordingly,the interfacial energies at 900,1000 and 1100℃ are 4.49±1.48,2.08±0.69 and 0.98±0.32 mJ.m-2,*** the diffusivities of solute element（s） at these temperatures are 3.41±1.08,30±9.5 and 145.15±45.85（10-15 m-2.s-1）,respectively.

关键词： Ni3 Al base intermetallic Coarsening kinetics Activation energy

Mechanical Relaxation of a Ti36.2Zr30.3Cu8.3Fe4be21.2 bulk Metallic Glass: Experiments and Theoretical Analysis

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Acta Metallurgica Sinica(English Letters) 2019年第6期32卷 726-732页

作者： J.C.Qiao Y.H.Chen G.J.Lyu k.k.Song J.M.Pelletier Y.Yao School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi'an 710072China School of Mechanical Electrical and Information EngineeringShandong University(Weihai)Weihai 264209China MATEIS UMR CNRS5510Bat.B.PascalINSA-LyonUniversite de Lyon69621 Villeurbanne CedexFrance

The dynamic mechanical relaxation behavior of Ti36.2Zr30.3Cu8.3Fe4be21.2 bulk metallic glass with good glass-forming ability was investigated by mechanical *** mechanical relaxation behavior was analyzed in the framework of quasi-point defects *** experimental results demonstrate that the atomic mobility of the metallic glass is closely associated with the correlation factorχ.The physical aging below the glass transition temperature T g shows a non-Debye relaxation behavior,which could be well described by stretched kohlrausch exponential *** kohlrausch exponentβaging reflects the dynamic heterogeneities of the metallic *** concentration of"defects"and atomic mobility decrease caused by the in situ successive heating during the mechanical spectroscopy experiments.

关键词： Metallic glasses Mechanical relaxation Physical aging Quasi-point defects

Feasibility study applied to mapping tidal effects in the Pannonian basin--An effort to check location dependencies atμGal level

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Geodesy and Geodynamics 2018年第3期9卷 237-245页

作者： G.Papp J.benedek P.Varga M.kis A.koppan b.Meurers R.Leonhardt M.k.baracza Geodetic and Geophysical Institute Research Centre for Astronomy and Earth SciencesHungarian Academy of Sciences.9400 SopronHungary Geological and Geophysical Institute of Hungary 1145 BudapestHungary University of Vienna Department of Meteorology and Geophysics1090 WienAustria Zentralanstalt fur Meteorologie and Geodynamik 1190 ViennaAustria University of Miskolc Department of Geophysics3515 Miskolc-EgyetemvarosHungary

This paper summarizes the main instrumental and methodological points of the tidal research which was performed in the framework of the National Scientific Research Fund Project k101603. Since the project is still running the tidal analysis results published here are only preliminary. Unmodelled tidal effects have been highlighted in some recent absolute gravity measurements carried out in the Pannonian basin resulting in a periodic modulation exceeding the typical standard deviations （±1microGal） of the drop sets. Since the most dominant source of the daily gravity variation is the bulk tidal effect, the goal of the project is to check its location dependency at bGal level. Unfortunately Hungary has had no dedicated instrumentation, so an effort was made to make the available LaCoste- Romberg spring G meters capable for continuous recording. As a reference instrument the GWR SG025 operated in the Conrad Observatory, Austria was also used and in the mean time of the project, a Scintrex CG-5 became also available, Eventually 6 instruments at 5 different locations were operated for 3 9 months mainly in co-located configuration. Although many experiments （moving mass calibrations） were done to determine the scale factors and scale functions of the instruments, the direct comparison of the tidal parameters obtained from the observations is still questionable. Therefore the ratio of the delta factors of O1 and M2 tidal constituents was investigated supposing that M2 is much more influenced by the ocean loading effect than O1. The slight detected increase of δ（O1 ）/δ（M2）（≈0.2%） toward east does not contradict to theory. This result has to be validated in the near future by analyzing available ocean loading models.

关键词： Gravity tide mapping Spring gravity meters Instrumental tests Co-located observations Location dependence of delta factors

COORDINATING A TWO-ECHELON SUPPLY CHAIN THROUGH DIFFERENT CONTRACTS UNDER PRICE AND PROMOTIONAL EFFORT-DEPENDENT DEMAND

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Journal of Systems Science and Systems Engineering 2013年第3期22卷 295-318页

作者： b.C.GIRI S.barDHAN T.MAITI Department of Mathematics Jadavpur UniversityIndia

Retail price and promotional effort are two important parameters on which demand of a commodity largely depends. This paper develops and analyzes a two-echelon supply chain where market demand depends on both retail price and sales effort. The centralized model is studied as the benchmark case, and the wholesale price-only contract is studied as the base case in which each entity tries to maximize its individual profit. Different contract mechanisms are implemented to outperform the base case in terms of both total chain＇s as well as individual profits. Comparisons among the coordinating contracts are provided so that any entity may choose the better one from available contracts after the contract parameters are negotiated. The model is extensively examined through a numerical example.

关键词： Price and effort-dependent demand wholesale price-only contract wholesale price discount revenue sharing profit sharing two-part tariff

CFD-DEM simulation of a pseudo-two-dimensional spouted bed comprising coarse particles

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Particuology 2019年第2期17卷 171-180页

作者： b. Mahmoodi S.H. Hosseini G. Ahmadi llam Gas Treating Company llam Iran Department of Chemical Engineering llam University llam 69315-516 Iran Department of Mechanical and Aeronautical Engineering Clarkson University Potsdam NY 13699-5725 USA

In the present study, computational fluid dynamics (CFD) and the discrete element method (DEM) are used in conjunction with the Eulerian-Lagrangian method to simulate a pseudo-two-dimensional spouted bed comprising coarse 6-mm particles. The open-source OpenFOAM code is used to solve the governing equations. The predicted vertical particle velocity along the bed axis, particle velocity profiles in the radial directi on, power spectral den sity, time-averaged particle velocity vectors, bed pressure drop, and solid flow pattern are evaluated and compared with existing experimental data. Good agreement is found between the CFD-DEM results and the measured data. It is also shown that the present CFD-DEM model accurately predicts the particle flow pattern throughout the bed. It is found that the drag force, solid stresses, and gravity play important roles in the CFD-DEM simulation of a spouted bed comprising coarse particles.

关键词： CFD-DEM Pseudo-2D spouted bed Hydrodynamics Coarse particles

Impedance spectroscopy study of Na_(2)SmV_(5)O_(15) ceramics

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Journal of Advanced Ceramics 2014年第1期3卷 1-6页

作者： P.S.DAS P.k.CHAkRAbORTY banarji bEHERA N.k.MOHANTY R.N.P.CHOUDHARY Department of Physics Midnapore CollegeMidnapore 721101India School of Physics Sambalpur UniversityBurla 768019SambalpurOdishaIndia Department of Physics ITERSiksha“O”Anusandhan UniversityBhubaneswar 751030OdishaIndia

The polycrystalline Na_(2)SmV_(5)O_(15)(NSV),a new member of the tungsten bronze(Tb)family,was prepared by a mixed-oxide *** room-temperature X-ray diffraction(XRD)confirmed the formation of single phase compound with orthorhombic crystal *** scanning electron microscopy(SEM)analysis indicated that the compound has homogeneous micrograph with a uniform distribution of small grains over the entire surface of the *** analysis of impedance spectra of NSV in a low-temperature range(-100℃to 100℃)at different frequencies exhibited interesting electrical properties like the contribution of bulk effect in conduction *** study of imaginary part of the impedance at different temperatures showed existence of relaxation peak with its shift towards higher frequency on increasing *** suggested the presence of frequency and temperature dependent relaxation process in the *** loss peak spectra were found to abide by Arrhenius law with small activation energy of 0.12 *** temperature dependence of AC and DC electrical conductivity(σ_(AC) and σ_(DC))was also obtained.

关键词： solid-state reaction microstructure impedance conductivity

Lanthanide NIR luminescence for telecommunications, bioanalyses and solar energy conversion

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Journal of Rare Earths 2010年第6期28卷 824-842页

作者： Jean-Claude G. bünzli Svetlana V. Eliseeva cole Polytechnique Fédérale de Lausanne Institute of Chemical Sciences and Engineering WCU Professor Korea University Center for Next Generation Photovoltaic Systems katholieke Universiteit Leuven Department of Chemistry Laboratory of Coordination Chemistry

Present-day advanced technologies heavily rely on the exciting magnetic and spectroscopic properties of lanthanide ions. In particular, their ability to generate well-characterized and intense near-infrared (NIR) luminescence is exploited in any modern fiber-optic telecommunication network. In this feature article, we first summarize the whereabouts underlying the design of highly luminescent NIR molecular edifices and materials. We then focus on describing the main trends in three applications related to this spectral range: telecommunications, biosciences, and solar energy conversion. In telecommunications, efforts concentrate presently on getting easily processable polymer-based waveguide amplifiers. Upconversion nanophosphors emitting in the visible after NIR excitation are now ubiquitous in many bioanalyses while their application to bio-imaging is still in its early stages; however, highly sensitive NIR-NIR systems start to be at hand for both in vitro and in vivo imaging, as well as dual probes combining magnetic resonance and optical imaging. Finally, both silicon-based and dye-sensitized solar cells benefit from the downconversion and upconversion capabilities of lanthanide ions to harvest UV and NIR solar light and to boost the overall quantum efficiency of these next-generation devices.

关键词： lanthanide luminescence near-infrared luminescence telecommunications bioanalysis solar energy conversion solar cell upconversion downconversion