Juan Tapia

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Cristina Guatimosim

Vivian Budnik

University of Massachusetts Medical School

Dlus

Academy of Sciences of the Czech Republic

Andreas Prokop

HYUNO KANG

Harvard University

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The University of Queensland, Australia

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Papers by Juan Tapia

The interscutularis muscle connectome

PLoS biology, 2009

The complete connectional map (connectome) of a neural circuit is essential for understanding its... more

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CPPM Mahine: A Synchronous Permanent Magnet Machine with Field Weakening

by Juan Tapia and Franco Leonardi

Due to its particular configuration, the Consequent Pole Permanent Magnet (CPPM) machine allows o... more Due to its particular configuration, the Consequent Pole Permanent Magnet (CPPM) machine allows one to easily control the airgap flux in a wide range so that the power capability of the machine is increased over a wide speed range. Two components of the flux, onealmost constant-coming from the permanent magnet located on the rotor surface of the machine, and the other -variable-coming from a field winding located in the middle of the stator, converge in the airgap characterizing the level of excitation of the machine. The field winding -when a variable DC current is injected-provides an adaptable level of excitation in both positive and negative directions respect to the PM magnetization. In this manner, control of the airgap flux can be obtained with a reduced amount of field MMF. A prototype using this configuration has been built and experimental results show that with 10% of the phase MMF it is possible to vary the flux in a range over +/-40%.

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Optimal design procedure for an external rotor permanent-magnet machine

2012 XXth International Conference on Electrical Machines, 2012

ABSTRACT External rotor machine design analytical algorithm is presented in this paper to calcula... more ABSTRACT External rotor machine design analytical algorithm is presented in this paper to calculate the main dimensions of the stator and rotor lamination. This procedure is based on the well known Lagrange multiplier method, where the airgap apparent power is maximized under tangential stress constraint Results of this procedure are used to generate an improved torque estimation algorithm based on the non-ideal structure of the machine. Finite element analysis is used to compare these results, establishing a good agreement with the analytical approach.

Robust Face Tracking with Locally-Adaptive Correlation Filtering

Lecture Notes in Computer Science

A face tracking algorithm based on locally-adaptive correla- tion filtering is proposed. The algo... more A face tracking algorithm based on locally-adaptive correla- tion filtering is proposed. The algorithm is capable to track a face with invariance to pose, gesticulations, occlusions and clutter. The target face is chosen at the beginning of the algorithm. Afterwards, a composite filter is designed to recognize the face in posterior frames. The filter is adapted online using information of current and past scene frames. The adaptive filter is constructed by combining several optimal templates designed for distortion invariant target recognition. Results obtained with the pro- posed algorithm using real-life scenes, are presented and compared with those obtained with a recent state-of-the-art tracking method, in terms of detection efficiency, tracking accuracy, and speed of processing.

Feasibility of different excitation methods of synchronous generators in island operation

by Janne Nerg and Juan Tapia

2012 XXth International Conference on Electrical Machines, 2012

Φ Abstract --This paper studies synchronous generators (SGs) with different excitations for islan... more Φ Abstract --This paper studies synchronous generators (SGs) with different excitations for island operation in which voltage or reactive power control is necessary. The main boundary conditions are defined. Three SGs with different excitations (traditional electrical excitation, permanent magnet excitation and hybrid excitation) are considered. The aim of the paper is to consider the feasibility of different hybrid excitation methods of SGs in island operation and choose the best one for a prototype building. The contribution of this paper is finding the best hybrid excitation solution for island operation, where an SG meets all the required boundary conditions. Index Terms -island operation, hybrid excitation synchronous machine, permanent magnet synchronous machine, synchronous machine, economical aspects Janne Nerg received the M.Sc.

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Estimación de la Función de Iluminación No Uniforme para la Restauración de Imágenes en un Procesador Gráfico

Un sistema en tiempo real es propuesto para restaurar imágenes degradadas por iluminación y ruido... more Un sistema en tiempo real es propuesto para restaurar imágenes degradadas por iluminación y ruido mediante los parámetros estadísticos de la escena de entrada. Se diseña un sistema de restauración de imágenes mediante el diseño de filtros, implementado en una unidad de procesamiento gráfico. El sistema es capaz de restaurar la escena de entrada que consiste en una imagen afectada por degradaciones en iluminación no uniforme y ruido aditivo con distribución normal. El filtro diseñado es capaz de adaptarse a las condiciones de la escena de entrada para estimar los parámetros estadísticos de la función de la fuente de iluminación. Los resultados obtenidos en simulación en CPU/GPU con el sistema propuesto se presentan en términos de desempeño de restauración de imágenes, complejidad computacional y tolerancia a iluminación de la escena de entrada y ruido aditivo.

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Saturated Reconstruction of a Volume of Neocortex

by Juan Tapia and Dongil Lee

Cell, 2015

We describe automated technologies to probe the structure of neural tissue at nanometer resolutio... more We describe automated technologies to probe the structure of neural tissue at nanometer resolution and use them to generate a saturated reconstruction of a sub-volume of mouse neocortex in which all cellular objects (axons, dendrites, and glia) and many sub-cellular components (synapses, synaptic vesicles, spines, spine apparati, postsynaptic densities, and mitochondria) are rendered and itemized in a database. We explore these data to study physical properties of brain tissue. For example, by tracing the trajectories of all excitatory axons and noting their juxtapositions, both synaptic and non-synaptic, with every dendritic spine we refute the idea that physical proximity is sufficient to predict synaptic connectivity (the so-called Peters&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; rule). This online minable database provides general access to the intrinsic complexity of the neocortex and enables further data-driven inquiries. VIDEO ABSTRACT.

hnRNP U protein is required for normal pre-mRNA splicing and postnatal heart development and function

by Juan Tapia, Junqiang Ye, and Lindsey Macpherson

Proceedings of the National Academy of Sciences of the United States of America, Jan 9, 2015

We report that mice lacking the heterogeneous nuclear ribonucleoprotein U (hnRNP U) in the heart ... more We report that mice lacking the heterogeneous nuclear ribonucleoprotein U (hnRNP U) in the heart develop lethal dilated cardiomyopathy and display numerous defects in cardiac pre-mRNA splicing. Mutant hearts have disorganized cardiomyocytes, impaired contractility, and abnormal excitation-contraction coupling activities. RNA-seq analyses of Hnrnpu mutant hearts revealed extensive defects in alternative splicing of pre-mRNAs encoding proteins known to be critical for normal heart development and function, including Titin and calcium/calmodulin-dependent protein kinase II delta (Camk2d). Loss of hnRNP U expression in cardiomyocytes also leads to aberrant splicing of the pre-mRNA encoding the excitation-contraction coupling component Junctin. We found that the protein product of an alternatively spliced Junctin isoform is N-glycosylated at a specific asparagine site that is required for interactions with specific protein partners. Our findings provide conclusive evidence for the essent...

Design and construction of a permanent magnet axial flux synchronous generator

1997 IEEE International Electric Machines and Drives Conference Record, 1997

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Electromagnetical design of surface mounted P.M. axial-flux synchronous motors

SPEEDAM 2010, 2010

Although permanent-magnet synchronous machine design is well known and has been treated in techni... more Although permanent-magnet synchronous machine design is well known and has been treated in technical literature, the non-linearity introduced by the saturation of the iron laminations has not been considered. This fact makes uncertain the calculation of the stator-rotor mutual reactance (Xm) and therefore the no-load voltage (Ef) is also undefined. Both inexactitudes have incidence on the power calculations. Especially sensitive is the determination of the power losses in the design procedure, because it is necessary to compare solutions with efficiencies over 95 per cent.. In this paper a straightforward calculation procedure of the flux and current densities for a given machine size, taking into consideration “exactly” any degree of saturation for a given current field oriented control angle is presented. The results obtained with this procedure match well with those obtained with finite element programs and with the values measured in an axial flux synchronous motor laboratory prototype.

A design procedure for a PM machine with extended field weakening capability

by Juan Tapia, Franco Leonardi, and Thomas Lipo

Conference Record of the 2002 IEEE Industry Applications Conference. 37th IAS Annual Meeting (Cat. No.02CH37344), 2002

A design procedure for the consequent pole permanent magnet (CPPM) machine is presented. Due to i... more A design procedure for the consequent pole permanent magnet (CPPM) machine is presented. Due to its double excitation nature (PM and field winding) and inherent three-dimensional flux distribution, an appropriate set of equations must be derived to model its magnetic structure. For practical operating conditions, radial, axial and tangential flux components are present. Therefore a convenient representation of the magnetic

Ultrastructurally smooth thick partitioning and volume stitching for large-scale connectomics

by Juan Tapia and Richard Fetter

Nature methods, Jan 16, 2015

Focused-ion-beam scanning electron microscopy (FIB-SEM) has become an essential tool for studying... more Focused-ion-beam scanning electron microscopy (FIB-SEM) has become an essential tool for studying neural tissue at resolutions below 10 nm × 10 nm × 10 nm, producing data sets optimized for automatic connectome tracing. We present a technical advance, ultrathick sectioning, which reliably subdivides embedded tissue samples into chunks (20 μm thick) optimally sized and mounted for efficient, parallel FIB-SEM imaging. These chunks are imaged separately and then 'volume stitched' back together, producing a final three-dimensional data set suitable for connectome tracing.

Cogging torque reduction in an axial flux PM machine with extended speed range

IEEE International Conference on Electric Machines and Drives, 2005., 2005

Cogging torque is a source of vibration and noise in PM machines. This torque is proportional to ... more Cogging torque is a source of vibration and noise in PM machines. This torque is proportional to the PM flux and the reluctance variation, and it is independent of the load current. In this paper, two methods for cogging torque reduction in an axial PM machine with field weakening capability is presented. The machine&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s rotor configuration considers two sections: one

Increasing field weakening capability of an axial flux PM machine

Conference Record of the 2004 IEEE Industry Applications Conference, 2004. 39th IAS Annual Meeting., 2004

In this paper an investigation related with the improvement of the field weakening capability for... more In this paper an investigation related with the improvement of the field weakening capability for an axial flux PM machine is carried out. The machine configuration proposed allows us to control the airgap flux, so that field weakening characteristic is obtained based in a negative d-axis current injection. This axial flux topology contains one central stator and two rotors. The

PERFORMANCE OF A MODIFIED EXTRUDER FOR POLYESTER FIBER PRODUCTION USING RECYCLED PET DESEMPE NO DE UN EXTRUSOR MODIFICADO PARA LA PRODUCCI ON DE FIBRA POLIESTER HECHAS DE PET RECICLADO

by Juan Tapia and Gabriel Luna-barcenas

Modelado de la biodegradación en biorreactores de lodos de hidrocarburos totales del petróleo int... more

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3D-FEA and experimental verification of the axial flux surface mounted PM machine parameters under saturated condition

International Universities Power Engineering Conference, 2004

A 3D-FEA of an axial flux PM machine for micro-generation applications is carried out. This analy... more A 3D-FEA of an axial flux PM machine for micro-generation applications is carried out. This analysis is oriented to determine dq-axis parameters under heavy saturation condition. In addition, experimental validation of these results is performed on a 9 kVA, 3Φ, 12-pole axial flux surface mounted PM machine prototype. The results show that a high nonlinearity is present in the dq-axis

Design of a 75 kW - 167 rpm axial-flux permanent magnet synchronous motor for copper mining applications

International Symposium on Power Electronics, Electrical Drives, Automation and Motion, 2006. SPEEDAM 2006., 2006

ABSTRACT The rise in energy costs in the last five years has compelled the copper mining industry... more ABSTRACT The rise in energy costs in the last five years has compelled the copper mining industry to encourage researchers to develop more efficient drives. It is under this scope that the authors of this paper are proposing the design optimization and construction of a 75 kW - 167 rpm central-stator permanent-magnet axial-flux synchronous-motor in order to drive, without any velocity adjustment mechanism, the flotation cell paddles used to concentrate the copper minerals. The geometrical quantities were optimized for maximum efficiency and the design incorporates in the data the load angle (delta). A 120degC as average temperature in the stator windings and demagnetizing effect were considered. Also cogging-torque reduction techniques are proposed and evaluated with a finite element software. The paper contains the complete algorithm and the results match those observed in an 8 kW laboratory prototype

Phase Equilibrium Modeling in Non-Reactive Systems Using Harmony Search

Stochastic Optimization - Seeing the Optimal for the Uncertain, 2011

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Pervasive Synaptic Branch Removal in the Mammalian Neuromuscular System at Birth

by Juan Tapia and Cristina Guatimosim

Neuron, 2012

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Inaugural Article by a Recently Elected Academy Member

Proceedings of The National Academy of Sciences, 2005

Fifty-eight cadherin-related protocadherin (Pcdh) genes are tandemly arrayed in three clusters (,... more Fifty-eight cadherin-related protocadherin (Pcdh) genes are tandemly arrayed in three clusters (, , and ) on mouse chromosome 18. The large number of clustered Pcdh family members, their presence at synapses, and the known binding specificities of other cadherin superfamily members all suggest that these Pcdhs play roles in specifying synaptic connectivity. Consistent with this idea, mice lacking all 22

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The interscutularis muscle connectome

PLoS biology, 2009

The complete connectional map (connectome) of a neural circuit is essential for understanding its... more

Download

CPPM Mahine: A Synchronous Permanent Magnet Machine with Field Weakening

by Juan Tapia and Franco Leonardi

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Optimal design procedure for an external rotor permanent-magnet machine

2012 XXth International Conference on Electrical Machines, 2012