Magnetic structure and orbital ordering in tetragonal and monoclinic KCrF3 from first-principles calculations

KCrF3 has been systematically investigated by using the full-potential linearized augmented plane wave plus local orbital method within the generalized gradient approximation and the local spin density approximation plus the on-site Coulomb repulsion approach. The total energies for ferromagnetic and three different antiferromagnetic configurations are calculated in the high-temperature tetragonal and low-temperature monoclinic phases, respectively.

Charge, orbital, and magnetic ordering in YBaFe2O5 from first-principles calculations

First principles calculations using the augmented plane wave plus local orbitals method, as implemented in the WIEN2k code, have been used to investigate the electronic and magnetic properties of YBaFe2O5, especially as regards the charge-orbital ordering. Although the total 3d charge disproportion is rather small, an orbital order parameter defined as the difference between t(2g) orbital occupations of Fe2+ and Fe3+ cations is large (0,73) and gives unambiguous evidence for charge and orbital ordering: Strong hybridization between O 2p and Fe e(g) states results in the nearly complete loss of the separation between the total charges at the Fe2+ and Fe3+ atoms.

Orbital ordering in Cs2AgF4 from first principles

First-principles calculations using the augmented plane wave plus local orbital method, as implemented in the WIEN2K code, have been used to investigate the structural, electronic, and magnetic properties of the layered perovskite Cs2AgF4. Our calculations indicate that an orthorhombic ground state for Cs2AgF4 is energetically favored over tetragonal. We also find that Cs2AgF4 should be a strong two-dimensional ferromagnet, with very weak antiferromagnetic coupling between the layers, in agreement with the experiment. More importantly, an antiferrodistortive ordering of z(2)-x(2) and z(2)-y(2) orbitals is inferred from the density of states and from a spin density isosurface analysis.

STUDY ON BONDING AND 4F ORBITAL EFFECT OF LANTHANIDE COMPOUNDS

The bonding and the 4f orbital effect of lanthanide elements at different valence state in their compounds have been studied by INDO method in this paper. The results obtained show that the bonding of lanthanide compounds is affected by many factors, such as valence state, ionic radius, ligand, coordinate number, space configuration etc. The strength of bonds composed of different ligands with lanthanide is distinctly different. The covalence of Ln-L bonds of lanthanide ions at high valence state in their compounds is larger than that at low valence state, The covalency at low coordinate number is larger than that at high coordinate number. Some lanthanide compounds with special configuration, besides sigma-bond, can form p(pi)-d(pi) dative bond with much overlap, which makes the Ln-L bond increase markedly. The effect of 4f orbitals on bonding is far less than that of 5d orbitals. The Ln 4f orbitals at 3 or 2 valence state may be considered to be essentially localized, while the contribution of 4f orbitals on bonding in 4 valent cerium compounds increases obviously, up to 1%.

Monitoramento orbital das queimadas em áreas indígenas e unidades de conservação no Brasil em 2001.

2002

Balanço do monitoramento orbital das queimadas no Brasil em 2001.

Resumo dos resultados obtidos ao longo do ano de 2001, sobre o monitoramento das queimadas no Brasil, enviado para a campanha de controle e redução das queimadas na agricultura brasileira, realizada pelo Ministério da Agricultura, Pecuária e Abastecimento (MAPA). A campanha pretende estimular o uso de alternativas tecnológicas na agricultura que substituam as queimadas, em especial nas regiões Norte e Centro-Oeste, uma das áreas mais atingidas por essa prática. A dinâmica das queimadas revelou um crescimento significativo em 2001 com relação ao ano anterior e várias surpresas, tanto na sua repartição espacial, detalhadas neste trabalho.

Monitoramento orbital de queimadas (Monitoramento, prevenção, controle das queimadas na agricultura brasileira): identificação de áreas críticas e prioritárias, 1997-1999.

Este documento resume os resultados da pesquisa realizada pela Embrapa Monitoramento por Satélite visando atender o Ministério da Agricultura e do Abastecimento, para identificação de áreas críticas no país quanto ao uso do fogo.

Progress in Vision and Robotics

The Vision Flashes are informal working papers intended primarily to stimulate internal interaction among participants in the A.I. Laboratory's Vision and Robotics group. Many of them report highly tentative conclusions or incomplete work. Others deal with highly detailed accounts of local equipment and programs that lack general interest. Still others are of great importance, but lack the polish and elaborate attention to proper referencing that characterizes the more formal literature. Nevertheless, the Vision Flashes collectively represent the only documentation of an important fraction of the work done in machine vision and robotics. The purpose of this report is to make the findings more readily available, but since they are not revised as presented here, readers should keep in mind the original purpose of the papers!

Experiences with a knowledge engineering toolkit: an assessment in industrial robotics

V. Robinson, N. W. Hardy, D. P. Barnes, C. J. Price, M. H. Lee. Experiences with a knowledge engineering toolkit: an assessment in industrial robotics. Knowledge Engineering Review, 2 (1):43-54, 1987.

Novelty and Habituation: the Driving Forces in Early Stage Learning for Developmental Robotics

Meng, Q., & Lee, M. (2005). Novelty and Habituation: the Driving Forces in Early Stage Learning for Developmental Robotics. Wermter, S., Palm, G., & Elshaw, M. (Eds.), In: Biomimetic Neural Learning for Intelligent Robots: Intelligent Systems, Cognitive Robotics, and Neuroscience. (pp. 315-332). (Lecture Notes in Computer Science). Springer Berlin Heidelberg.

Novelty and Habituation: the Driving Forces in Early Stage Learning for Developmental Robotics

Q. Meng and M. H. Lee, Novelty and Habituation: the Driving Forces in Early Stage Learning for Developmental Robotics, AI-Workshop on NeuroBotics, University of Ulm, Germany. September 2004.