DC-Amplifier-Input-Offset-Voltage Control in a Constant-Temperature Thermoresistive-Sensor-Measurement Instrument

In this paper, the effect of dc amplifier input offset voltage on the static and dynamic performances of a generic constant-temperature thermoresistive-sensor-feedback circuit (CTC) is reviewed. A negative-feedback automatic control circuit for the input offset voltage is proposed in order to assure a stable operation of the CTC and to obtain optimal response time. Experimental evaluation results of the proposed circuit performance are presented     

Multiple biological sequence alignment in heterogeneous multicore clusters with user-selectable task allocation policies

Multiple Sequence Alignment (MSA) is an important problem in Bioinformatics that aims to align more than two sequences in order to emphasize similarity regions. This problem is known to be NP-Hard, so heuristic methods are used to solve it. DIALIGN-TX is an iterative heuristic method for MSA that generates alignments by concatenating ungapped regions with high similarity. Usually, the first phase of MSA algorithms is parallelized by distributing several independent tasks among the nodes. Even though heterogeneous multicore clusters are becoming very common nowadays, very few task allocation policies were proposed for this type of architecture. This paper proposes an MPI/OpenMP master/slave parallel strategy to run DIALIGN-TX in heterogeneous multicore clusters, with several allocation policies. We show that an appropriate choice of the master node has great impact on the overall system performance. Also, the results obtained in a heterogeneous multicore cluster composed of 4 nodes (30 cores), with real sequence sets show that the execution time can be drastically reduced when the appropriate allocation policy is used.     

A Variational Approach to Video Registration with Subspace Constraints

This paper addresses the problem of non-rigid video registration, or the computation of optical flow from a reference frame to each of the subsequent images in a sequence, when the camera views deformable objects. We exploit the high correlation between 2D trajectories of different points on the same non-rigid surface by assuming that the displacement of any point throughout the sequence can be expressed in a compact way as a linear combination of a low-rank motion basis. This subspace constraint effectively acts as a trajectory regularization term leading to temporally consistent optical flow. We formulate it as a robust soft constraint within a variational framework by penalizing flow fields that lie outside the low-rank manifold. The resulting energy functional can be decoupled into the optimization of the brightness constancy and spatial regularization terms, leading to an efficient optimization scheme. Additionally, we propose a novel optimization scheme for the case of vector valued images, based on the dualization of the data term. This allows us to extend our approach to deal with colour images which results in significant improvements on the registration results. Finally, we provide a new benchmark dataset, based on motion capture data of a flag waving in the wind, with dense ground truth optical flow for evaluation of multi-frame optical flow algorithms for non-rigid surfaces. Our experiments show that our proposed approach outperforms state of the art optical flow and dense non-rigid registration algorithms.     

Robust image-based visual servoing using invariant visual information

This paper deals with the use of invariant visual features for visual servoing. New features are proposed to control the 6 degrees of freedom of a robotic system with better linearizing properties and robustness to noise than the state of the art in image-based visual servoing. We show in this paper that by using these features the behavior of image-based visual servoing in task space can be significantly improved. Several experimental results are provided and validate our proposal.     

Detecting malicious tweets in trending topics using a statistical analysis of language

Twitter spam detection is a recent area of research in which most previous works had focused on the identification of malicious user accounts and honeypot-based approaches. However, in this paper we present a methodology based on two new aspects: the detection of spam tweets in isolation and without previous information of the user; and the application of a statistical analysis of language to detect spam in trending topics. Trending topics capture the emerging Internet trends and topics of discussion that are in everybody’s lips. This growing microblogging phenomenon therefore allows spammers to disseminate malicious tweets quickly and massively. In this paper we present the first work that tries to detect spam tweets in real time using language as the primary tool. We first collected and labeled a large dataset with 34 K trending topics and 20 million tweets. Then, we have proposed a reduced set of features hardly manipulated by spammers. In addition, we have developed a machine learning system with some orthogonal features that can be combined with other sets of features with the aim of analyzing emergent characteristics of spam in social networks. We have also conducted an extensive evaluation process that has allowed us to show how our system is able to obtain an F-measure at the same level as the best state-of-the-art systems based on the detection of spam accounts. Thus, our system can be applied to Twitter spam detection in trending topics in real time due mainly to the analysis of tweets instead of user accounts.     

Study of Nanostructured Array of Antidots Using Pulsed Magnetic Fields

The absence of the superparamagnetic limit in nanostructured antidots makes them strong candidates for ultra-high density recording media. In this work, nanoporous alumina templates (NpATs), with average pore diameters ～35 nm and separation ～100 nm, were grown using a two-step anodization method. A Ni₈₀Fe₂₀ thin film of 6.5 nm was then sputtered on top of such NpATs, building an antidot network. A detailed study of the magnetoresistance (MR) (fields up to 25 T and temperatures down to 77 K) was performed. The antidot network sample revealed an anomalous MR and R(T) behaviour at T _M ～250 K arising from a spin-flip transition occurring in a thin iron oxide layer.     

Equipment selection and justification through total productivity model

Traditional methods of economic analysis to justify equipment selection and use are based on several methods such as the Net Present Value, Break-Even Analysis, Pay-Back Period, Return on Investment, among others. However, with the introduction of automation, Flexible Manufacturing Systems (FMS), and Computer Integrated Manufacturing Systems (CIMS), such economic analyses have often resulted in decisions that management did not like to support but did not have much choice to avoid on account of pressure from manufacturing engineers, design engineers and others in the operations areas. The real problem of equipment selection and justification lies in the methodologies used.

This paper presents a unique approach to equipment justification by applying Sumanth's TOTAL PRODUCTIVITY MODEL, whereby the anticipated impact of the proposed equipment on profitability is assessed from the point of total productivity and the five partial productivities. Then, only if the equipment increases the total productivity level beyond its break even point, the equipment is selected or justified.

This method offers a non-traditional approach to justifying and selecting equipment in all types of environment. A numerical example is presented by using LOTUS 1-2-3^TM on an IBM PC. Advantages and limitations to this approach are discussed to provide a balanced perspective on the important issue of equipment selection and justification.     

Measuring Magnetoresistance in a 2D Intergranular Magnetic-Semiconducting Material

A new 2D intergranular semiconducting-magnetic material obtained by depositing magnetic clusters of permalloy in a doped Si surface, is presented. The material, exhibiting ohmic contacts, has an ample range of properties and versatility by simply controlling deposition time. We can have clusters separated by relatively large, intermediate distances or a continuous film. This permits to study the magnetic and electrical properties of the clusters mediated by currents through the n-doped Si. We observe anisotropic and giant magnetoresistances of and between clusters. Also, by preventing oxidation of the Si surface, we suggest the possibility of formation of magnetic Si up to 205 K. The material reported here is technologically promising since it is grown directly on Si and its magnetoresistance of up to 1.5% is obtained at low fields and RT. The spin transfer occurs for long distances since the current flows coherently from cluster to cluster via the Si matrix. The method developed may be also adequate to study superconductivity properties of isolated or weakly percolative clusters by coupling through Josephson currents. The system is diluted when clusters are separated on average by 50 nm. This could help to better understand dilute magnetic semiconductor materials in general. We also put forward a method to distinguish univocally giant from anisotropic magnetoresistance by depositing a thin film of gold and comparing magnetic properties by spin transfer through Si or metal.     

Yttrium oxide based metal-insulator-semiconductor structures on silicon

Yttrium oxide based metal-insulator-semiconductor (MIS) structures on silicon have been studied. Yttrium films of thickness of nearly 200 Å were deposited by electron beam evaporation on silicon substrates held at room temperature. The oxidation of yttrium was performed at 750 °C for 1 h in dry oxygen. Scanning electron microscopy showed a smooth surface morphology for oxidized films. X-ray diffraction analyses were also performed, but did not confirm the crystalline nature of the oxide. Capacitance-voltage and current-voltage measurements were conducted to characterize aluminum-yttrium oxide-silicon MIS structures. The results have demonstrated the potential of using yttrium oxide as a gate dielectric.