Planar antenna design and channel modeling for chip-scale communications

The need to handle the communication demands of growing multicore processors have created a framework where Wireless Network-on-Chip (WNoC) appears as a promising complement to wired chip interconnects. In this thesis, a planar antenna design is proposed to characterize the yet largely unknown wireless channel within realistic chip packages. This work addresses the issue by modeling a flip-chip package and designing an antenna at 250 GHz, seeking it to be readily integrable in the package and the enabler of a low-loss (although probably highly reverberating) wireless channel across the package.Through simulation-based parametric studies of antenna and package configurations, and placing multiple antennas in the package, path losses and delay spread measurements are obtained to characterize the deterministic channel within a chip. We demonstrate that a wireless link around 220--230 GHz in a reverberant cavity on top of the chip package can be created with patch antennas, achieving a path loss in the range of 2--10 dB and delay spreads in the sub-nanosecond range, although time-domain results are limited in our case to computational constraints of the simulations.La necesidad de gestionar las demandas de comunicación de los crecientes procesadores multinúcleo ha creado un marco en el que las redes inalámbricas en chip (Wireless Network-on-Chip, WNoC) aparecen como un prometedor complemento a las interconexiones de chip por cable. En esta tesis se propone un diseño de antena planar para caracterizar el canal inalámbrico, aún muy desconocido, dentro de paquetes de chips realistas. Este trabajo aborda la cuestión mediante el modelado de un paquete flip-chip y el diseño de una antena a 250 GHz, buscando que sea fácilmente integrable en el paquete y el habilitador de un canal inalámbrico de baja pérdida (aunque probablemente altamente reverberante) a través del paquete.A través de estudios paramétricos basados en simulaciones de configuraciones de antena y paquete, y colocando múltiples antenas en el paquete, se obtienen pérdidas de trayectoria y mediciones de propagación de retardo para caracterizar el canal determinista dentro de un chip. Demostramos que es posible crear un enlace inalámbrico en torno a 220-230 GHz en una cavidad reverberante en la parte superior del encapsulado del chip con antenas de parche, consiguiendo path losses del orden de 2-10 dB y un delay spread en el rango de los sub-nanosegundos, aunque los resultados en el dominio del tiempo están limitados en nuestro caso por las restricciones computacionales de las simulaciones.La necessitat de gestionar les demandes de comunicació dels creixents processadors multinucli ha creat un marc en què les xarxes sense fils en xip (Wireless Network-on-Chip, WNoC) apareixen com un prometedor complement a les interconnexions de xip per cable. En aquesta tesi es proposa un disseny d'antena planar per caracteritzar el canal sense fil, encara molt desconegut, dins de paquets de xips realistes. Aquest treball aborda la qüestió mitjançant el modelatge d'un paquet flip-chip i el disseny d'una antena a 250 GHz, buscant que sigui fàcilment integrable al paquet i l'habilitador d'un canal sense fil de baixa pèrdua (encara que probablement altament reverberant) del paquet. A través d'estudis paramètrics basats en simulacions de configuracions d'antena i paquet, i col·locant múltiples antenes al paquet, s'obtenen pèrdues de trajectòria i mesuraments de propagació de retard per caracteritzar el canal determinista dins d'un xip. Demostrem que és possible crear un enllaç sense fils al voltant de 220-230 GHz en una cavitat reverberant a la part superior de l'encapsulat del xip amb antenes de pegat, aconseguint path losses de l'ordre de 2-10 dB i un delay spread en el rang dels subnanosegons, encara que els resultats en el domini del temps estan limitats en el nostre cas per les restriccions computacionals de les simulacions

An equal educational opportunity for language minority students: A legal analysis of language education after Lau

An Equal Educational Opportunity for Language Minority Students: A Legal Analysis of Language Education After Lau is a legal/historical study that examined the current legal standards applicable to the education of language minority students in the United States. This was achieved by analyzing the jurisprudence emerging from the interpretation and application of the Lau v. Nichols Supreme Court decision; Several questions were considered during the research of this dissertation. These included: How has the legal precedent established in Lau v. Nichols been interpreted and applied by subsequent law cases involving the education of language minority students? What role has the Office for Civil Rights played in securing compliance with the Lau precedent? What are the legal implications for school administrators in providing programs for language minority students?;The significance of this study was found in examining the jurisprudence following Lau concerned with a language minority student\u27s right to an equal educational opportunity in America\u27s schools. This study will benefit school level and program administrators responsible for organizing and implementing programs for language minority students by serving as a resource for providing legally sound programs for language minority students; This dissertation used an analytical, qualitative research design. As a legal/historical analysis, it included search, selection and criticism of the sources, presentation of facts and generalizations, and the use of inductive case law analysis. Law cases were examined for their usage of Lau as a precedent; Included in this study is a history of language minority education in the United States, the Federal government\u27s involvement in the education of language minority students, the role of the Office for Civil Rights, and an analysis of the Supreme Court\u27s landmark decision in Lau v. Nichols

Efecte del tractament de brunyit en els acers inoxidables austenítics metaestables

Els acers inoxidables austenítics metastables formen part de la família d’acers d’alta resistència, els quals presenten unes excel·lents propietats com són: la seva conformabilitat, soldabilitat conjuntament amb una elevada resistència a la corrosió i una bona capacitat d’absorbir energia. Per això, tot i tenint un important desavantatge com és el seu baix límit elàstic, aquests acers han despertat un gran interès i es presenten com a principals candidats per a la seva aplicació com a materials estructurals. L’objectiu d’aquest projecte, és aconseguir millorar les propietats mecàniques superficials i microestructurals d’un acer inoxidable austenític metastable EN 1.4318, mitjançant un tractament superficial de brunyit. Una de les principals característiques d’aquest tipus d’acer, és la capacitat de transformar una fase austenítica a martensítica per una deformació plàstica. Per analitzar els efecte d’aquest tractament, s’han estudiat dues condicions inicials de l’acer, diferenciades segons el seu contingut de martensita. La primera mostra es troba en un estat de recuit, on el percentatge de martensita no supera l’1% i la segona prové directament del procés de laminació en fred, això comporta que aquesta presenti un 38% de martensita. Paral·lelament, en el mateix grup de recerca s’han estudiat dues mostres més, amb les quals compararem els resultats al llarg d’aquest treball, una d’elles presenta un 10% de fase martensítica inicial i l’altre té un contingut de martensita del 18%. El tractament de brunyit s’ha dut a terme aplicant diferents condicions, les quals poden alterar els efectes produïts pel brunyit amb bola damunt la superfície. Aquestes condicions són l’assistència amb vibració o sense ella en l’eina de brunyir, la direcció en la que s’ha dut a terme el brunyit (paral·lela o perpendicular al laminat) i realitzar el procés en una o cinc passades. Les mostres tractades s’han caracteritzat a nivell superficial, mitjançant observació per microscòpia òptica confocal i SEM (microscòpia electrònica de rastreig). També, s’ha fet una caracterització mecànica efectuant mesures de la duresa en la secció transversal per indentació instrumentada. Els resultats manifesten de manera clara, que s’assoleix una millora més significativa de les propietats mecàniques de la mostra en estat de recuit. A més, els resultats destaquen en aquelles condicions de brunyit en les que no s’aplica vibració a l’eina, es brunyeix amb cinc passades i en la direcció perpendicular al laminat

A continuous Mott transition between a metal and a quantum spin liquid

More than half a century after first being proposed by Sir Nevill Mott, the deceptively simple question of whether the interaction-driven electronic metal-insulator transition may be continuous remains enigmatic. Recent experiments on two-dimensional materials suggest that when the insulator is a quantum spin liquid, lack of magnetic long-range order on the insulating side may cause the transition to be continuous, or only very weakly first order. Motivated by this, we study a half-filled extended Hubbard model on a triangular lattice strip geometry. We argue, through use of large-scale numerical simulations and analytical bosonization, that this model harbors a continuous (Kosterlitz-Thouless-like) quantum phase transition between a metal and a gapless spin liquid characterized by a spinon Fermi surface, i.e., a "spinon metal." These results may provide a rare insight into the development of Mott criticality in strongly interacting two-dimensional materials and represent one of the first numerical demonstrations of a Mott insulating quantum spin liquid phase in a genuinely electronic microscopic model.Comment: 18 pages, 9 figure

Constructing topological models by symmetrization: A PEPS study

Symmetrization of topologically ordered wavefunctions is a powerful method for constructing new topological models. Here, we study wavefunctions obtained by symmetrizing quantum double models of a group $G$ in the Projected Entangled Pair States (PEPS) formalism. We show that symmetrization naturally gives rise to a larger symmetry group $\tilde G$ which is always non-abelian. We prove that by symmetrizing on sufficiently large blocks, one can always construct wavefunctions in the same phase as the double model of $\tilde G$. In order to understand the effect of symmetrization on smaller patches, we carry out numerical studies for the toric code model, where we find strong evidence that symmetrizing on individual spins gives rise to a critical model which is at the phase transitions of two inequivalent toric codes, obtained by anyon condensation from the double model of $\tilde G$.Comment: 10 pages. v2: accepted versio

Making use of the complementarity of hydropower and variable renewable energy in Latin America: A probabilistic analysis

Latin America is one of the regions most vulnerable to the effects of climate variability on hydropower generation. Hydropower is the backbone of the Latin-American power system and a key technology for ensuring low-carbon power generation in the region. Despite its importance, our understanding of the impact and likelihood of seasonal variability and of long-term phenomena such as the El Niño Southern Oscillation (ENSO) on hydropower is limited. There is an essential need to understand how likely these effects are and to identify measures to counterbalance them. A combination of wind, solar, and hydropower offers the potential to mitigate the impact of climate variability on renewable power generation and thus improve its reliability. Here we present a modeling framework to quantify the potential benefits of such combination. The modeling framework relies on a meteorological reanalysis dataset, large-scale renewable power generation models, and statistic models. We consider the countries with the largest hydropower capacity in the region, namely Argentina, Brazil, Colombia, Mexico, and Venezuela. We examine whether the probability of a production deficit is reduced when all renewable resources are combined compared to a scenario based solely on hydropower, especially during droughts. The approach presented allows for the first time an in-depth analysis of the benefits of a combined wind, solar, and hydropower-based power generation under different geographical conditions in altered ENSO phases. Our results suggest that—depending on the country and the percentile—the hydropower generated during drought ENSO phases could be up to 50% lower than that during neutral phases. The countries most affected are Colombia and Venezuela, while the reduction is somewhat less severe in Argentina, Brazil, and Mexico. Combining hydropower with variable renewable energy (VRE) offers the potential to reduce the risk of a power deficit during the 10th percentile of the driest months of the year, both in drought and neutral phases. Argentina is the country with the most effective combination of resources to mitigate a power deficit, as each MW of installed VRE generates 0.218 GWh of additional power. It is followed by Brazil and Mexico with 0.185 GWh per MW of VRE and by Venezuela and Colombia with 0.128–0.098 GWh/MW of VRE, respectively. These results can contribute to informing future decisions on capacity planning and regional transmission grids

The Trichoptera of Panama XIII. Further new country records for caddisflies (Insecta: Trichoptera) from the Republic of Panama

The Republic of Panama currently includes 414 recorded species of Trichoptera. Herein we add two new genera (Hydroptilidae: Angrisanoia Ozdikmen, 2008 and Mayatrichia Mosely, 1937) and 17 new country records (Philopotamidae: Chimarra (C.) tapanti Blahnik, Wormaldia bolivari Muñoz-Quesada and Holzenthal, and Wormaldia zunigae Muñoz-Quesada and Holzenthal; Hydropsychidae: Centromacronema pygmaeum Botosaneanu; Hydroptilidae: Brysopteryx esparta Harris and Holzenthal, Byrsopteryx solisi Harris and Holzenthal, Costatrichia falsa Santos, Takiya, and Nessimian, Mayatrichia illobia Harris and Holzenthal, Metrichia amplitudinis Bueno-Soria and Holzenthal, Ochrotrichia boquillas Moulton and Harris, O. conformalis Bueno-Soria and Holzenthal, O. quinealensis Bueno-Soria and Holzenthal, and O. unica Bueno-Soria and Santiago; Leptoceridae: Triaenodes morai Holzenthal and Andersen; Odontoceridae: Marilia kingsolveri Bueno-Soria and Rojas-Ascencio; and, Helicopsychidae: Helicopsyche alajuela Johanson and Holzenthal and Helicopsyche breviterga Flint) to Panama’s caddisfly fauna. The newly recorded taxa increase Panama’s total known caddisfly fauna to 431 species, distributed among 15 families and 55 genera. These results are part of an ongoing effort to characterize the caddisfly fauna of Panama, and to evaluate the aquatic insect diversity of the country’s major watersheds (cuencas). La República de Panamá actualmente incluye 414 especies registradas de Trichoptera. Aquí agregamos dos nuevos géneros (Hydroptilidae: Angrisanoia Ozdikmen, 2008 y Mayatrichia Mosely, 1937) y 17 nuevos registros para el país (Philopotamidae: Chimarra (C.) tapanti Blahnik, Wormaldia bolivari Muñoz-Quesada y Holzenthal, y Wormaldia zunigae Muñoz-Quesada y Holzenthal; Hydropsychidae: Centromacronema pygmaeum Botosaneanu; Hydroptilidae: Brysopteryx esparta Harris y Holzenthal, Byrsopteryx solisi Harris y Holzenthal, Costatrichia falsa Santos, Takiya, y Nessimian, Mayatrichia illobia Harris y Holzenthal, Metrichia amplitudinis Bueno-Soria y Holzenthal, Ochrotrichia boquillas Moulton y Harris, Ochrotrichia conformalis Bueno-Soria y Holzenthal, Ochrotrichia quinealensis Bueno-Soria y Holzenthal, y Ochrotrichia unica Bueno-Soria y Santiago; Leptoceridae: Triaenodes morai Holzenthal y Andersen; Odontoceridae: Marilia kingsolveri Bueno-Soria y Rojas- Ascencio; y, Helicopsychidae: Helicopsyche alajuela Johanson y Holzenthal y Helicopsyche breviterga Flint) a la fauna de Trichoptera de Panamá. Los taxones recien reportados aumentan el total de la fauna de Trichoptera de Panamá a 431 especies, distribuidas en 15 familias y 55 géneros. Estos resultados son parte de un esfuerzo continuo para caracterizar la fauna de Trichoptera y para evaluar la diversidad de insectos acuáticos de las principales cuencas hidrográficas (cuencas) de Panamá

A silent speech system based on permanent magnet articulography and direct synthesis

In this paper we present a silent speech interface (SSI) system aimed at restoring speech communication for individuals who have lost their voice due to laryngectomy or diseases affecting the vocal folds. In the proposed system, articulatory data captured from the lips and tongue using permanent magnet articulography (PMA) are converted into audible speech using a speaker-dependent transformation learned from simultaneous recordings of PMA and audio signals acquired before laryngectomy. The transformation is represented using a mixture of factor analysers, which is a generative model that allows us to efficiently model non-linear behaviour and perform dimensionality reduction at the same time. The learned transformation is then deployed during normal usage of the SSI to restore the acoustic speech signal associated with the captured PMA data. The proposed system is evaluated using objective quality measures and listening tests on two databases containing PMA and audio recordings for normal speakers. Results show that it is possible to reconstruct speech from articulator movements captured by an unobtrusive technique without an intermediate recognition step. The SSI is capable of producing speech of sufficient intelligibility and naturalness that the speaker is clearly identifiable, but problems remain in scaling up the process to function consistently for phonetically rich vocabularies

Neural control of dynamic 3-dimensional skin papillae for cuttlefish camouflage.

The colour and pattern changing abilities of octopus, squid and cuttlefish via chromatophore neuro-muscular organs are unparalleled. Cuttlefish and octopuses also have a unique muscular hydrostat system in their skin. When expressed, dermal bumps called papillae disrupt body shape and imitate the fine texture of surrounding objects, yet the control system is unknown. Here we report for papillae: (i) the motoneurons and the neurotransmitters that control activation and relaxation, (ii) a physiologically fast expression and retraction system, and (iii) a complex of smooth and striated muscles that enables long-term expression of papillae through sustained tension in the absence of neural input. The neural circuits controlling acute shape-shifting skin papillae in cuttlefish show homology to the iridescence circuits in squids. The sustained-tension in papillary muscles for long-term camouflage utilizes muscle heterogeneity, and points toward the existence of a "catch-like" mechanism that would reduce the necessary energy expenditure.This work was funded by an AFOSR grant no. FA9550-14-1-0134 , Isaac Newton Trust/Wellcome Trust ISSF/University of Cambridge Joint Research Grant ( 097814/Z/11/Z ) to P.T.G-B., and a Biotechnology and Biological Sciences Research Council David Phillips Fellowship (BBSRC, BB/L024667/1 ) to T.J.W