7,642 research outputs found
Catch Crops in Organic Farming Systems without Livestock Husbandry - Simulations with the DAISY model
This paper presents simulations of the soil-plant-atmosphere model DAISY based on an organic crop rotation with incorporation of different catch crops following pea as a leguminous cash crop. Special emphasise was put on the simulation of N-mineralisation/-immobilisation and of soil microbial biomass N. The DAISY model was able to simulate soil mineral N and soil microbial biomass N after soil incorporation of catch crop plant residues to some extend. Several processes need further attention and may be integrated into the DAISY model: (1) soil tillage induced mobilisation of organic material including considerable amounts of organic N, (2) winter killing of sensitive plant species and varieties, (3) decomposition of plant residues at the soil surface as occurring after winter killing, (4) decomposition of easily decomposable plant residues at low temperatures, (5) soil microbial residues as an organic pool temporarily protected against turnover. Furthermore, reliable criteria for the subdivision of green plant residues into an easily decomposable pool and a more recalcitrant pool have to be developed
Overview of the 2005 cross-language image retrieval track (ImageCLEF)
The purpose of this paper is to outline efforts from the 2005 CLEF crosslanguage image retrieval campaign (ImageCLEF). The aim of this CLEF track is to explore
the use of both text and content-based retrieval methods for cross-language image retrieval. Four tasks were offered in the ImageCLEF track: a ad-hoc retrieval from an historic photographic collection, ad-hoc retrieval from a medical collection, an automatic image annotation task, and a user-centered (interactive) evaluation task that is explained in the iCLEF summary. 24 research groups from a variety of backgrounds and nationalities (14 countries) participated in ImageCLEF. In this paper we describe the ImageCLEF tasks, submissions from participating groups and summarise the main fndings
Heterogeneous volatility cascade in financial markets
Using high frequency data, we have studied empirically the change of
volatility, also called volatility derivative, for various time horizons. In
particular, the correlation between the volatility derivative and the
volatility realized in the next time period is a measure of the response
function of the market participants. This correlation shows explicitly the
heterogeneous structure of the market according to the characteristic time
horizons of the differents agents. It reveals a volatility cascade from long to
short time horizons, with a structure different from the one observed in
turbulence. Moreover, we have developed a new ARCH-type model which
incorporates the different groups of agents, with their characteristic memory.
This model reproduces well the empirical response function, and allows us to
quantify the importance of each group.Comment: 10 pages, 2 figures, To be published in Physica
Catch Crops in Organic Farming Systems without Livestock Husbandry - Model Simulations
During the last years, an increasing number of stockless farms in Europe converted to organic farming practice without re-establishing a livestock. Due to the lack of animal manure as a nutrient input, the relocation and the external input of nutrients is limited in those organic cropping systems. The introduction of a one-year green manure fallow in a 4-year crop rotation, including clover-grass mixtures as a green manure crop is the classical strategy to solve at least some of the problems related to the missing livestock. The development of new crop rotations, including an extended use of catch crops and annual green manure (legumes) may be another possibility avoiding the economical loss during the fallow year.
Modelling of the C and N turnover in the soil-plant-atmosphere system using the soil-plant-atmosphere model DAISY is one of the tools used for the development of new organic crop rotations. In this paper, we will present simulations based on a field experiment with incorporation of different catch crops.
An important factor for the development of new crop rotations for stockless organic farming systems is the expected N mineralisation and immobilisation after incorporation of the plant materials. Therefore, special emphasise will be put on the simulation of N-mineralisation/-immobilisation and of soil microbial biomass N. Furthermore, particulate organic matter C and N as an indicator of remaining plant material under decomposition will be investigated
Discontinuous Galerkin Finite Element Convergence for Incompressible Miscible Displacement Problems of Low Regularity
In this article we analyse the numerical approximation of incompressible miscible displacement problems with a combined mixed finite element and discontinuous Galerkin method under minimal regularity assumptions. The main result is that sequences of discrete solutions weakly accumulate at weak solutions of the continuous problem. In order to deal with the non-conformity of the method and to avoid overpenalisation of jumps across interelement boundaries, the careful construction of a reflexive subspace of the space of bounded variation, which compactly embeds into , and of a lifting operator, which is compatible with the nonlinear diffusion coefficient, are required. An equivalent skew-symmetric formulation of the convection and reaction terms of the nonlinear partial differential equation allows to avoid flux limitation and nonetheless leads to an unconditionally stable and convergent numerical method. Numerical experiments underline the robustness of the proposed algorithm
Stable unidimensional arrays of coherent strained islands
We investigate the equilibrium properties of arrays of coherent strained
islands in heteroepitaxial thin films of bidimensional materials. The model we
use takes into account only three essential ingredients : surface energies,
elastic energies of the film and of the substrate and interaction energies
between islands via the substrate. Using numerical simulations for a simple
Lennard-Jones solid, we can assess the validity of the analytical expressions
used to describe each of these contributions. A simple analytical expression is
obtained for the total energy of the system. Minimizing this energy, we show
that arrays of coherent islands can exist as stable configurations. Even in
this simple approach, the quantitative results turn out to be very sensitive to
some details of the surface energy.Comment: 24 pages, 7 figures. to be published in Surface Scienc
Håndbog i opklaring af fødevare- eller vandbårne sygdomsudbrud:Publikation nr.: 2017-28-800-06947
Generation of single-frequency tunable green light in a coupled ring tapered diode laser cavity
Transformation with rol-genes of <em>Agrobacterium rhizogenes</em> as a strategy to breed compact ornamental plants with improved postharvest quality
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