TaXEm: a tool for aiding the evaluation of domain topic.

The notorious advances in textual information storage need fast and effcient tools to organize, retrieve and browse this information and tools for knowledge extraction. A very interesting way to organize specific domain information is the topic taxonomy building. Moreover a great challenge in this research area is the result evaluation and validation. This evaluation can be carried out through objective measures or through a subjective analysis, which is based on the domain specialist judgment. The measures CQM and SQM [1] are used to evaluate a generated taxonomy against a reference taxonomy. A reference taxonomy is constructed by human and consolidated through its community use along the years. The CQM is used to evaluate the generated taxonomy relatively to the selected descriptors for each taxonomy node; on the other hand, the SQM is used to evaluate the taxonomy structure. As these objective measures do not encompass the specialist knowledge, the specialist evaluation is very important. However the human evaluation is expensive, because this task involves readiness, time and dedication from the specialists. In this way, the TaXEm tool claims to reduce the subjective evaluation costs. The TaXEm (Taxonomia em XML da Embrapa) tool offers subsidies for carrying out a taxonomy (semi)automatic evaluation, which allows the user to implement some automatic evaluation before going on a subjective evaluation.Propor 2010. Demonstration

Analysis of decomposition parameters of green manure in the Brazilian Northeast with Association Rules Networks.

Modern agricultural processes are increasingly looking at the use of chemicals, so the constant search for organic alternatives to fertilization becomes frequent. The use of data mining using association rule networks (ARN) can aid in the analysis of the parameters involved in choosing which plant to use as green manure. In this work, an analysis of the parameters of green manures used in the Brazilian Northeast is presented, demonstrating the applicability of the computational technique as well as its use to gain in productivity

Facilitando a avaliação de taxonomias de tópicos automaticamente geradas no domínio do agronegócio.

O custo de avaliação de taxonomias automaticamente geradas costuma ser alto se realizado exclusivamente por especialistas do domínio. Neste trabalho propõe-se uma forma de validação objetiva para o vocabulário automaticamente obtido, com o qual uma taxonomia automaticamente gerada é representada. Para isso, o vocabulário gerado é comparado ao de uma taxonomia pré-existente, já validada, bem aceita e que use um thesaurus ou dicionário específico do domínio. Como taxonomias validadas foram utilizadas algumas árvores da Agência de Informação Embrapa e como vocabulário padrão o contido no Thesagro.SBIAgro 2009

Easily labelling hierarchical document clusters.

One of the problems of automatic models that generate topic taxonomies is the process of creating the most significant term list that discriminates each document group. In this paper, a new method to label document hierarchical clusters is proposed, which is completely independent from the clustering method. This method automatically decides the number of the words in each label list, avoids word repetitions in a tree branch and provides a kind of cutting for the cluster tree. The obtained results were tested as search queries in a retrieval process and showed a very good performance. Additionally, the use of the method was experimented by some specialists in the text collection domain, trying to evaluate their understanding and expectations over the results

Theory for phonon pumping by magnonic spin currents

In recent years several experimental observations and theoretical predictions of unique phenomena involving the interplay between spin currents and the coupled magnetization-elastic dynamics have invigorated the field of spintronics. One important experiment reported several years ago showed that elastic waves can produce spin pumping, that is, generation of spin currents in a metallic film in contact with a ferromagnetic material. Very recently the Onsager reciprocal of this effect has been observed in samples made of a film of the insulating ferrimagnet yttrium iron garnet in contact with a platinum strip with nanoscopic silver particles that is known to exhibit a giant spin Hall effect. By passing an electric current through the metallic strip, the spin current generated by the spin Hall effect produces a large magnonic spin current that excites phonons with microwave frequency, observed by Brillouin light scattering. Here we show that these experiments are explained by a theory based on a process in which one magnon in the spin current creates one phonon and another magnon, with conservation of energy and momentum. The theoretical value of the critical charge current in the metallic strip necessary to drive phonons and the values of the phonon frequencies are in good agreement with the values measured experimentally

Dirac-Surface-State-Dominated Spin to Charge Current Conversion in the Topological Insulator (Bi0.22Sb0.78)2Te3(Bi_{0.22}Sb_{0.78})_2Te_3 Films at Room Temperature

We report the spin to charge current conversation in an intrinsic topological insulator (TI) $(Bi_{0.22}Sb_{0.78})_2Te_3$ film at room temperature. The spin currents are generated in a thin layer of permalloy (Py) by two different processes, spin pumping (SPE) and spin Seebeck effects (SSE). In the first we use microwave-driven ferromagnetic resonance of the Py film to generate a SPE spin current that is injected into the TI $(Bi_{0.22}Sb_{0.78})_2Te_3$ layer in direct contact with Py. In the second we use the SSE in the longitudinal configuration in Py without contamination by the Nernst effect made possible with a thin NiO layer between the Py and $(Bi_{0.22}Sb_{0.78})_2Te_3$ layers. The spin-to-charge current conversion is attributed to the inverse Edelstein effect (IEE) made possible by the spin-momentum locking in the electron Fermi contours due to the Rashba field. The measurements by the two techniques yield very similar values for the IEE parameter, which are larger than the reported values in the previous studies on topological insulators.Comment: 18 pages and 7 figure

Spin-to-charge conversion and interface-induced spin Hall magnetoresistance in yttrium iron garnet/metallic bilayers

We report the investigation of spin-to-charge current interconversion process in hybrid structures of yttrium iron garnet (YIG)/metallic bilayers by means of two different experimental techniques: spin pumping effect (SPE) and spin Hall magnetoresistance (SMR). We demonstrate the evidence of a correlation between spin-to-charge conversion and SMR in bilayers of YIG/Pd, YIG/Pt, and YIG/IrMn. The correlation was verified directly in the spin Hall angles and the amplitudes of the voltage signals measured by the SPE and SMR techniques. The detection of SMR was carried out using the modulated magnetoresistance technique and lock-in amplifier detection. For these measurements, we present a simple model for the interpretation of the results. The results allow us to conclude that indeed the interface in the YIG/metallic bilayers has a dominant role in the spin-to-charge current conversion and SMR

Model for chaotic dynamics of the perpendicular-pumping spin-wave instability

We propose a model for the dynamics of spin-wave instabilities driven by a rf field perpendicular to the dc magnetic field in the second- order Suhl process. We show that a self-oscillation arises from the dynamic nonlinear interaction between the k=0 mode driven by the pumping field and a degenerate k≠0 magnon, with frequency that depends on the dissipation rates and the nonlinear interaction parameters and not on the sample dimensions. For certain parameter values, as the driving field increases we find a period-doubling route to chaos and odd-period bifurcation windows consistent with recent experiments in yttrium iron garnet