1,931 research outputs found
Reverse electrodialysis – Multi effect distillation heat engine fed by lithium chloride solutions
Salinity Gradient Heat Engines (SG-HEs) have been proposed as a promising technology for converting low-temperature heat into electricity. The SG-HE includes two different processes: (i) a salinity gradient process where the salinity gradient between two solutions is converted into electricity and (ii) a thermal regeneration process where low-grade heat (T<100°C) is used to re-establish the original salinity gradient of the two streams. Among the proposed working solutions, aqueous solution of lithium chloride has been identified as one of the most promising thanks to its remarkable solubility and activity. In this work, a process model to study the performance of a SG-HE constituted by a Reverse ElectroDialysis (RED) unit coupled with a Multi Effect Distillation (MED) unit fed with lithium chloride solution is presented. The influence of the concentration of the inlet solution in the RED unit and the temperature difference in the evaporators of the MED unit on the performance were evaluated by considering ideal membranes. Furthermore, the impact of membrane permselectivity and resistance on the system performance was evaluated. Results showed promising system efficiencies, making this technology attractive for conversion of low-grade heat (<100°C) into electricity, but membrane properties should be enhanced
On the (2,3)-generation of the finite symplectic groups
This paper is a new important step towards the complete classification of the
finite simple groups which are -generated. In fact, we prove that the
symplectic groups are -generated for all . Because
of the existing literature, this result implies that the groups
are -generated for all , with the exception of and
Scott's formula and Hurwitz groups
This paper continues previous work, based on systematic use of a formula of
L. Scott, to detect Hurwitz groups. It closes the problem of determining the
finite simple groups contained in for which are Hurwitz,
where is an algebraically closed field. For the groups , ,
and the Janko groups and it provides explicit -generators
More on regular subgroups of the affine group
This paper is a new contribution to the study of regular subgroups of the
affine group , for any field . In particular we associate to any
partition of abelian regular subgroups in such a
way that different partitions define non-conjugate subgroups. Moreover, we
classify the regular subgroups of certain natural types for . Our
classification is equivalent to the classification of split local algebras of
dimension over . Our methods, based on classical results of linear
algebra, are computer free
The -generation of the finite unitary groups
In this paper we prove that the unitary groups are
-generated for any prime power and any integer . By
previous results this implies that, if , the groups and
are -generated, except when
.Comment: In this version, we obtained a complete classification of the finite
simple unitary groups which are (2,3)-generated; some proofs have been
semplifie
The simple classical groups of dimension less than 6 which are (2,3)-generated
In this paper we determine the classical simple groups of dimension r=3,5
which are (2,3)-generated (the cases r = 2, 4 are known). If r = 3, they are
PSL_3(q), q 4, and PSU_3(q^2), q^2 9, 25. If r = 5 they are PSL_5(q), for
all q, and PSU_5(q^2), q^2 >= 9. Also, the soluble group PSU_3(4) is not
(2,3)-generated. We give explicit (2,3)-generators of the linear preimages, in
the special linear groups, of the (2,3)-generated simple groups.Comment: 12 page
Effect of farming system changes on life cycle assessment indicators for dairy farms in the Italian Alps.
In some Alpine areas dairy farming is going through a process of intensification with significant changes in farming systems. The aim of this study was to investigate environmental performance of a sample of 31 dairy farms in an Alpine area of Lombardy with different levels of intensification. A cradle to farm gate life cycle assessment was performed including the following impact categories: land use, non-renewable energy use, climate change, acidification and eutrophication. From a cluster analysis it resulted that the group of farms with lowest environmental impacts were characterized by low stocking density and production intensity; farms that combined good environmental performances with medium gross margins were characterized also by high feed self-sufficiency and lowland availability. Environmental impacts of dairy farms in the mountain areas could be mitigated by the improvement of forage production and quality and by the practice of summer highland grazing, that significantly reduced eutrophication per kg of milk of the less self-sufficient farms
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