16,753 research outputs found
Non-Linear Effects in Resonant Tunneling; Bistabilities and Self-Sustained Oscillating Currents
We study non-linear phenomena in double barrier heterostructures. Systems in
3D under the effect of an external magnetic field along the current and 1D
systems are analyzed. Non-linearities are reflected in the I-V characteristic
curve as bistabilities, instabilities and time dependent oscillations of the
currents. The nature of the non-linear behavior depends upon the parameters
that define the system.Comment: 3 pages, 2 figures, accepted for publication in Superlattices and
Microstructure
Desenvolvimento de um laboratório de ciências para os primeiros anos de escolaridade
A presente comunicação visa apresentar uma proposta de laboratório de ciências para os primeiros anos de escolaridade. Assim, pretende-se: (i) fundamentar a relevância de infraestruturas, equipamentos e recursos de suporte ao ensino das ciências e apresentar princÃpios orientadores apontados pela literatura para o desenvolvimento de laboratórios escolares e (ii) descrever o processo de concepção, validação e implementação inerente ao desenvolvimento de um laboratório de ciências numa escola do 1.º Ciclo do Ensino Básico (CEB), tendo por base o marco teórico de suporte ao desenvolvimento do mesmo
Rigorous Formulation of Duality in Gravitational Theories
In this paper we evince a rigorous formulation of duality in gravitational
theories where an Einstein like equation is valid, by providing the conditions
under which the Hodge duals (with respect to the metric tensor g) of T^a and
R_b^a may be considered as the torsion and curvature 2-forms associated with a
connection D', part of a Riemann-Cartan structure (M,g',D'), in the cases g =
g' and g does not equal g', once T^a and R_b^a are the torsion and curvature
2-forms associated with a connection D part of a Riemann-Cartan structure
(M,g,D). A new form for the Einstein equation involving the dual of the Riemann
tensor of D is also provided, and the result is compared with others appearing
in the literature.Comment: 15 page
Urban energy simulation based on 3d city models: a service-oriented approach
Recent advancements in technology has led to the development of sophisticated software tools revitalizing growth in different domains. Taking advantage of this trend, urban energy domain have developed several compute intensive physical and data driven models. These models are used in various distinct simulation softwares to simulate the whole life-cycle of energy flow in cities from supply, distribution, conversion, storage and consumption. Since some simulation software target a specific energy system, it is necessary to integrate them to predict present and future urban energy needs. However, a key drawback is that, these tools are not compatible with each other as they use custom or propriety formats. Furthermore, they are designed as desktop applications and cannot be easily integrated with third-party tools (open source or commercial). Thereby, missing out on potential model functionalities which are required for sustainable urban energy management. In this paper, we propose a solution based on Service Oriented Architecture (SOA). Our approach relies on open interfaces to offer flexible integration of modelling and computational functionality as loosely coupled distributed services
Sugar-hydrolysing enzymes in gustatory mutants of Drosophila
The distribution of the isozymes of α-glucosidase in different parts of Drosophila melanogaster was examined. Two of the eight glucosidase bands are associated with tarsi. The gustatory mutations in the genes gustB and gustC greatly reduce tarsal glucosidase activity, but the enzyme deficiency is not correlated with inability to taste sugars
The low dimensional dynamical system approach in General Relativity: an example
In this paper we explore one of the most important features of the Galerkin
method, which is to achieve high accuracy with a relatively modest
computational effort, in the dynamics of Robinson-Trautman spacetimes.Comment: 7 pages, 5 figure
Structural and insulator-to-metal phase transition at 50 GPa in GdMnO3
We present a study of the effect of very high pressure on the orthorhombic
perovskite GdMnO3 by Raman spectroscopy and synchrotron x-ray diffraction up to
53.2 GPa. The experimental results yield a structural and insulator-to-metal
phase transition close to 50 GPa, from an orthorhombic to a metrically cubic
structure. The phase transition is of first order with a pressure hysteresis of
about 6 GPa. The observed behavior under very high pressure might well be a
general feature in rare-earth manganites.Comment: 4 pages, 3 figures and 2 table
Corrosion Control of Kunifer-5 Seawater Piping Systems of Naval Ships by Cathodic Protection Technique
The cause of premature corrosion of Kunifer-5(copper alloy containing Ni 5 per cent and Fe 1.35 per cent) pipes used in seawater piping systems on board ships for feeding seawater to various units has been discussed. It has been shown that the Kunifer-5 alloys suffer from heavy corrosion-erosion attack at unavoidable bends and places where local seawater velocity exceeds the specified limit. The field observations as well as laboratory study have indicated that satisfactory protection of the pipes could be achieved by galvanic cathodic protection using aluminium alloy anodes
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