Search results for " agglomeration"
showing 10 items of 69 documents
First-principles insight into CO hindered agglomeration of Rh and Pt single atoms on m-ZrO2
2020
In this first-principles study we evaluate the thermodynamic and kinetic stability of Rh and Pt single-atoms (SAs) and subnano clusters on the monoclinic zirconia surface with and without a CO atmosphere. To address the kinetic stability and agglomeration of SAs to clusters and nanoparticles, a non-equilibrium nanothermodynamic approach is developed and parametrised using data computed with density functional theory. The bare subnano clusters are more stable than SA and become more so with increasing size, which means the agglomeration is always favoured. CO binds strongly to the single atoms and clusters, and our atomistic thermodynamics treatment indicates that some CO will be present eve…
Effect of processing temperature and mixing time on the properties of PP/GnP nanocomposites
2020
Abstract During processing of molten polymers the thermal and mechanical stress acting on the melt in presence of oxygen can induce degradation with a modification of the chemical structure of the polymers. This picture can become even more relevant if the melt is a multiphasic polymer system. In this last case, the effects of the degradation depend also on the presence of a second phase and on the interactions between the two phases. In this work, the effect of the processing conditions, temperature and time, have been considered in order to investigate the thermo-mechanical and thermo-oxidative degradation of nanocomposites made by polypropylene and different contents of graphene nanoplat…
A Multi-scalar Approach to Long-Term Dynamics, Spatial Relations and Economic Networks of Roman Secondary Settlements in Italy and the Ombrone Valley…
2019
AbstractIn Roman landscapes, the particular sites defined as secondary settlements (also known as vici/villages, minor centres, agglomérations secondaires and/or stationes/mansiones) have played an ‘intermediary’ role between the cities and other rural structures (villae/farms), linked to medium- and long-distance economic and commercial trajectories. The aim of this paper is to apply a multi-scalar approach to model their long-term spatial relationships and connectivity with the Mediterranean exchange network. On the macro-scale, we have analysed a sample of 219 reviewed sites to understand the diachronic trends and spatial dynamics of attraction/proximity to significant elements of the la…
Estimating Verdoorn law for Italian firms and regions
2011
In empirical regional economics, returns to scale are typically estimated at the regional level in search for evidence on alternative theories of growth and agglomeration. However, returns to scale may also have a firm-level dimension. In this paper, we exploit micro level data and estimate the dynamic Verdoorn law in a multilevel-setting, where returns to scale are obtained simultaneously for the micro and the regional level. Using Italian firm-level data and the NUTS-3 level of aggregation, we estimate the classic and augmented versions of Verdoorn law for the manufacturing sector, and the rest of the economy for comparison. Our results show that increasing returns to scale co-exist at bo…
Welfare, Home Market Effects, and Horizontal Foreign Direct Investment
2005
We investigate the spatial distribution and organization of an imperfectly competitive industry when firms may choose to operate more than a single production unit. Focusing on a short-run setting with a fixed mass of firms, we fully characterize the spatial equilibria analytically. Comparing the equilibrium and the first-best, we show that both organizational and spatial inefficiencies may arise. In particular, when fixed costs are low enough the market outcome may well lead to overinvestment and, therefore, to too many multinationals operating from a social point of view. Furthermore, once multinationals are taken into account, the market outcome may well lead too little agglomeration.
Regional Inequality and Product Variety
2005
We investigate how differences in set-up costs of various types affect the trade-off between global efficiency and spatial equity and show that the standard assumption of symmetry in fixed costs masks the existence of an interesting effect: the range of available varieties varies depends on the spatial distribution of firms. In such a setting, even when the market outcome leads to excessive agglomeration under symmetric fixed costs, a planner opts for asymmetric fixed costs and more agglomeration. The reason is that the losses induced by more agglomeration are offset by the gains due to additional product variety.
Agglomeration and dispersion of economic activities in and around Paris: An exploratory spatial data analysis
2010
The agglomeration patterns of twenty-six manufacturing and service sectors in and around Paris in 1999 are analysed. The method used measures the intensity of spatial agglomeration and identifies the location patterns of economic sectors. First the locational Gini coefficient and Moran’s I statistics of global spatial autocorrelation are computed. These provide different but complementary information about the spatial agglomeration of the sectors under study. Then exploratory spatial data analysis tools are applied. Moran scatterplots and local indicators of spatial association statistics reveal great diversity in location patterns across sectors.
Modéliser la suburbanisation
2002
L’histoire de la suburbanisation de la population et de l’emploi, principalement aux Etats-Unis, permet d’identifier trois caracteristiques du phenomene. 1/ La suburbanisation se traduit par un etalement urbain tel que population et emploi s’accroissent plus en peripherie qu’au centre. 2/ La suburbanisation fait emerger de nouvelles concentrations d’activites dans la peripherie des villes-centres et donne naissance a des structures urbaines multicentriques. 3/ La suburbanisation differencie les contenus et les fonctions economiques des centres et recompose les centralites urbaines. Dans ce cadre, la suburbanisation se presente selon des modalites differentes selon les epoques et les regions…
Evaluation of advanced silica packings for the separation of biopolymers by high-performance liquid chromatography
1984
Abstract In the separation of proteins and peptides by the various modes of high-performance liquid chromatography, the nature of the substrates requires the use of microparticulate silica packings with bonded ligands of appropriate design. Agglomeration of monodisperse silica hydrosols of defined size distribution into beaded particles provides a useful method of controlling the pore size, the size distribution, the particle porosity and surface area of these packings. The particle porosity is shown to be a major factor governing the packing density and packing stability of the column. For size-exclusion chromatography of proteins, parent silicas of pore size 10 and 100 nm with a narrow po…
Vacancies and Carbon Impurities in Iron
1981
Point defects in electron-irradiated high-purity α-iron have been studied by positron lifetime measurements. We show that the migration stage of monovacancies occurs already as low as at 220 K, which results in agglomeration of small three-dimensional vacancy clusters. Furthermore, we irradiated carbon-doped iron specimens, where formation of highly asymmetric monovacancycarbon atom pairs was detected during the migration stage of monovacancies at 220 K.