Search results for "Compact"
showing 10 items of 531 documents
APPROXIMATION OF BANACH SPACE VALUED NON-ABSOLUTELY INTEGRABLE FUNCTIONS BY STEP FUNCTIONS
2008
AbstractThe approximation of Banach space valued non-absolutely integrable functions by step functions is studied. It is proved that a Henstock integrable function can be approximated by a sequence of step functions in the Alexiewicz norm, while a Henstock–Kurzweil–Pettis and a Denjoy–Khintchine–Pettis integrable function can be only scalarly approximated in the Alexiewicz norm by a sequence of step functions. In case of Henstock–Kurzweil–Pettis and Denjoy–Khintchine–Pettis integrals the full approximation can be done if and only if the range of the integral is norm relatively compact.
Analytic capacity and quasiconformal mappings with $W^{1,2}$ Beltrami coefficient
2008
We show that if $\phi$ is a quasiconformal mapping with compactly supported Beltrami coefficient in the Sobolev space $W^{1,2}$, then $\phi$ preserves sets with vanishing analytic capacity. It then follows that a compact set $E$ is removable for bounded analytic functions if and only if it is removable for bounded quasiregular mappings with compactly supported Beltrami coefficient in $W^{1,2}$.
Effects of soil compaction, rain exposure and their interaction on Soil Carbon Dioxide emission
2012
Soils release more carbon per annum than current global anthropogenic emissions (Luo and Zhou, 2006). Soils emit carbon dioxide through mineralization and decomposition of organic matter and respiration of roots and soil organism (Houghton 2007) Evaluation of the effects of abiotic factors on microbial activity is of major importance in the context of mitigation greenhouse gases emissions. One of the key greenhouse gases is carbon dioxide (CO2) and previous studies demonstrate that soil CO2 emission is significantly affected by temperature and soil water content. There are a limited number of studies that examine the impact of bulk density and soil surface characteristics as a result of exp…
Multivariate geostatistics for assessing and predicting soil compaction
2005
The aim of this research is to investigate the potential of geostatistical techniques for understanding and evaluating the spatial variability of soil compaction, caused by the traffic of agricultural machines and/or the action of tillage implements. Soil cone penetrometer resistance was measured in a field of inland Sicily, along a transect of 3 m length, from the soil surface until 70 cm depth. The 3D mean maps showed a random variation on the surface and a high spatial correlation among penetrometer resistance data measured at different depths. The map corresponding to five tractor passes showed the largest extension of the areas characterised by the highest values of penetrometer resist…
Survey of the mean pressure exerted by a wide range of tractors on the soil
2010
In order to predict the mean pressure exerted by a vehicle tyre on the soil, in 1984 Plackett suggested measuring the contact area of a tyre on a hard surface. The model proposed by Hallonborg in 1996, based on the “super ellipse theory”, provided the best results in terms of prediction of the tyre-soil contact area. In this study 82 4WD tractors with different power, mass and age of manufacture were surveyed. Relying on their technical features, the contact area of the front and rear tyres of each tractor and, therefore, their pressure on the soil was calculated, in order to assess the attention paid by manufacturers to soil compaction. The results of this survey showed that the mean press…
Long-term monitoring of soil bulk density and erosion rates in two Prunus Persica (L) plantations under flood irrigation and glyphosate herbicide tre…
2021
Abstract Early season fruit production for the northern European market is highly intensive in fertilization, machinery, irrigation and the use of herbicides. Those conditions increase the soil losses and soil compaction and threaten the Sustainable Goals for Development of the United Nations by 2030. Long-term soil erosion measurements are necessary to determine the sustainability of agriculture managements. Moreover, soil erosion on flood irrigation land is a topic that request more surveys and research as rainfed sloping terrains attracted all the attention of scientists and research investment. Improved Stock Unearthing Method (ISUM) was applied to two 15 years-old herbicide treated fie…
Composition operators on the Schwartz space
2018
[EN] We study composition operators on the Schwartz space of rapidly decreasing functions. We prove that such a composition operator is never a compact operator and we obtain necessary or sufficient conditions for the range of the composition operator to be closed. These conditions are expressed in terms of multipliers for the Schwartz class and the closed range property of the corresponding operator considered in the space of smooth functions.
On the space of all regular operators from C(K) into C(K)
1988
AbstractIt is known that Lr(E, C(K)), the space of all regular operators from E into C(K), is a Riesz space for all Riesz spaces E if and only if K is Stonian. We prove that this statement holds if E is replaced by C(K), where K is a compact space, the cardinal number of which satisfies a certain condition.
Quantitative Analysis of Experimental and Synthetic Microstructures for Sedimentary Rock
1999
A quantitative comparison between the experimental microstructure of a sedimentary rock and three theoretical models for the same rock is presented. The microstructure of the rock sample (Fontainebleau sandstone) was obtained by microtomography. Two of the models are stochastic models based on correlation function reconstruction, and one model is based on sedimentation, compaction and diagenesis combined with input from petrographic analysis. The porosity of all models closely match that of the experimental sample and two models have also the same two point correlation function as the experimental sample. We compute quantitative differences and similarities between the various microstructur…
Dynamics of the Selkov oscillator.
2018
A classical example of a mathematical model for oscillations in a biological system is the Selkov oscillator, which is a simple description of glycolysis. It is a system of two ordinary differential equations which, when expressed in dimensionless variables, depends on two parameters. Surprisingly it appears that no complete rigorous analysis of the dynamics of this model has ever been given. In this paper several properties of the dynamics of solutions of the model are established. With a view to studying unbounded solutions a thorough analysis of the Poincar\'e compactification of the system is given. It is proved that for any values of the parameters there are solutions which tend to inf…