Pathological element-based active device models and their application to symbolic analysis

This paper proposes new pathological element-based active device models which can be used in analysis tasks of linear(ized) analog circuits. Nullators and norators along with the voltage mirror-current mirror (VM-CM) pair (collectively known as pathological elements) are used to model the behavior of active devices in voltage-, current-, and mixed-mode, also considering parasitic elements. Since analog circuits are transformed to nullor-based equivalent circuits or VM-CM pairs or as a combination of both, standard nodal analysis can be used to formulate the admittance matrix. We present a formulation method in order to build the nodal admittance (NA) matrix of nullor-equivalent circuits, where the order of the matrix is given by the number of nodes minus the number of nullors. Since pathological elements are used to model the behavior of active devices, we introduce a more efficient formulation method in order to compute small-signal characteristics of pathological element-based equivalent circuits, where the order of the NA matrix is given by the number of nodes minus the number of pathological elements. Examples are discussed in order to illustrate the potential of the proposed pathological element-based active device models and the new formulation method in performing symbolic analysis of analog circuits. The improved formulation method is compared with traditional formulation methods, showing that the NA matrix is more compact and the generation of nonzero coefficients is reduced. As a consequence, the proposed formulation method is the most efficient one reported so far, since the CPU time and memory consumption is reduced when recursive determinant-expansion techniques are used to solve the NA matrix.Promep-Mexico UATLX-PTC-088Junta de Andalucía TIC-2532Ministerio de Educación y Ciencia TEC2007-67247, TEC2010-14825UC-MEXUS-CONACyT CN-09-31

Systematic Derivation for Quadrature Oscillators Using CCCCTAs

According to 16 nullor-mirror models of the current-controlled current conveyor transconductance amplifier (CCCCTA) and using nodal admittance matrix (NAM) expansion method, three different classes of the double-mode quadrature oscillators employed CCCCTAs and two grounded capacitors are synthesized. The class I oscillators have 32 different forms, the class II oscillators have 16 different forms, and the class III oscillators have four different forms. In all, 52 quadrature oscillators using CCCCTAs are obtained. Having used canonic number of components, the circuits are easy to be integrated and the condition for oscillation and the frequency of oscillation can be tuned by tuning bias currents of the CCCCTAs. The circuit analysis and simulation results have been included to support the generation method

Symbolic analysis of analog circuits containing voltage mirrors

7 páginas, 7 figuras, 2 tablas, 4 imágenes.-- Open Access: This article is distributed under the terms of the Creative Commons Attribution Noncommercial License.The pathological elements voltage mirror (VM) and current mirror (CM) have shown advantages in analog behavioral modeling and circuit synthesis, where many nullor-mirror equivalences have been explored to design and to transform voltage-mode circuits to current-mode ones and viceversa. However, both the VM and CM have not equivalents to perform automatic symbolic circuit analysis. In this manner, we introduce nullor-equivalents for these pathological elements allowing to include parasitics and to perform only symbolic nodal analysis. The nullor-equivalent of the CM is extended to provide multiple-outpus (MO-CM). Finally, two active filters containing VMs, CMs and MO-CMs are analysed to show the usefulness of the models.This work is supported by: UC-MEXUS and CONACyT under grants CN-09-310 and 48396-Y; by Promep-Mexico under grant UATLX-PTC-088; by Consejeria de Innovacion, Ciencia y Empresa, Junta de Andalucia-Spain TIC-2532; and by the JAE-Doc program of CSIC co-funded by FSE, Spain.Peer reviewe

LIGHT AND AFFECTS FROM A COMPARATIVE POINT OF VIEW

Light metaphors occurring in Chinese philosophy and Stoicism are of special interest for the unique ways they channel potentialities of the self. In this paper I apply ideas from cognitive linguistics to examine selected structural features of these metaphors. I also build on these ideas by presenting a framework regarding affects to assist in disclosing what is at stake for differing Chinese and Stoic technologies of the self. The paper adopts a high-level perspective to see these broad philosophical implications, interleaving discussions of Chinese philosophy (mainly views associated with Daoism), Stoicism (bringing into relief important differences from these views), and contemporary research on socially constructed affects. This triadic comparative approach aims to shed new light on some root assumptions built into the projects of self-cultivation that are at the core of Chinese and Stoic worldviews

Behavioral Modeling of Mixed-Mode Integrated Circuits

Open Access.-- et al.This work is partially supported by CONACyT through the grant for the sabbatical stay of the first author at University of California at Riverside, during 2009-2010. The authors acknowledge the support from UC-MEXUS-CONACYT collaboration grant CN-09-310; by Promep México under the project UATLX-PTC-088, and by Consejeria de Innovacion Ciencia y Empresa, Junta de Andalucia, Spain, under the project number TIC-2532. The third author thanks the support of the JAE-Doc program of CSIC, co-funded by FSE.Peer Reviewe

An innovative approach to simulate thrombosis with smoothed particle hydrodynamics

La trombosi è una patologia che porta alla formazione di coaguli, che possono provocare ostruzioni arteriose e, infine, migrano attraverso il sistema cardiocircolatorio causando infarto, ictus o embolia polmonare. Il processo è abbastanza complesso ed il suo meccanismo non è ancora chiaro, essendo il risultato dell’interazione tra diversi fattori, compresa l'attivazione e l'aggregazione piastrinica, le reazioni chimiche e l'emodinamica.È fondamentale considerare e ridurre al minimo la formazione di trombi nella progettazione e realizzazione di organi artificiali, come valvole cardiache artificiali o protesi. Lo studio dell'emodinamica può fornire un supporto efficace per identificare e prevenire il rischio di trombosi.A causa della mancanza di soluzioni analitiche adeguate e della complessità degli studi sperimentali, la ricerca evolve sempre più verso l’utilizzo delle simulazioni numeriche Questa tesi mira a modellare la formazione, la crescita e l'evoluzione del trombo mediante il metodo numerico accoppiato Smoothed Particle Hydrodynamics (SPH) usando un modello di interazione fluido-struttura (FSI). Il modello proposto descrive le principali fasi della cascata coagulativa attraverso l'equilibrio di quattro specie biochimiche e tre tipologie di piastrine. Le particelle SPH possono passare dalla fase fluida a quella solida se sono soddisfatte delle specifiche condizioni biochimiche e fisiche. L'accoppiamento fluido-solido è modellato introducendo legami elastici tra le particelle solide senza nessuna interfaccia. Per raggiungere questo obiettivo, in primo luogo il modello viene validato confrontando i risultati numerici con i dati sperimentali disponibili in letteratura, in secondo luogo, il nuovo codice numerico è applicato per descrivere la trombosi in appendice atriale in caso di fibrillazione o come trombosi indotta in aneurismi cerebrali.Thrombosis is a pathology leading to the formation of clots, that can result in arterial obstructions and, eventually, migrate through the cardiocirculatory system causing heart attack, stroke or pulmonary embolism. The process is complex and its mechanism is still unclear, being the result of the interaction between various factors, including platelet activation and aggregation, chemical reactions, and hemodynamics.It is crucial to consider and minimise thrombosis in the design and implementation of artificial organs, such as artificial heart valves, and vascular prostheses. The study of hemodynamics can provide effective support to identify and prevent the risk of thrombosis.Due to the lack of adequate analytical solutions and the complexity of experimental studies, research increasingly evolves towards the use of computational methods.This thesis aims at modelling the formation, growth and evolution of thrombus by means of a Smoothed Particle Hydrodynamics (SPH) numerical method coupled with a fluid-structure interaction (FSI) model. The proposed model describes the main phases of the coagulative cascade through the balance of four biochemical species and three types of platelets. SPH particles can switch from fluid to solid phase whenspecific biochemical and physical conditions are satisfied. Fluid-solid coupling is modelled by introducing elastic binds between solid particles, without requiring detention and management of the interface between the two media.In order to reach this goal, firstly the model is validated by comparing the numerical prediction with experimental data available in the literature, secondly, it is applied to describe thrombosis formation due to relevant pathologies such as atrial fibrillation and cerebral aneurysms where the insertion of flow diverter creates thrombogenic stasis zone

Band alignment at metal/ferroelectric interfaces: insights and artifacts from first principles

Based on recent advances in first-principles theory, we develop a general model of the band offset at metal/ferroelectric interfaces. We show that, depending on the polarization of the film, a pathological regime might occur where the metallic carriers populate the energy bands of the insulator, making it metallic. As the most common approximations of density functional theory are affected by a systematic underestimation of the fundamental band gap of insulators, this scenario is likely to be an artifact of the simulation. We provide a number of rigorous criteria, together with extensive practical examples, to systematically identify this problematic situation in the calculated electronic and structural properties of ferroelectric systems. We discuss our findings in the context of earlier literature studies, where the issues described in this work have often been overlooked. We also discuss formal analogies to the physics of polarity compensation at LaAlO3/SrTiO3 interfaces, and suggest promising avenues for future research.Comment: 29 pages, 23 figure

Things Fall Apart and Chinua Achebe’s Postcolonial Discourse

Chinua Achebe, the contemporary Nigerian novelist, is considered as one of the prominent figures in African anti-colonial literature. What makes his works specific is the way he approaches the issues of colonization of Africa in an objective manner and through an innovative language which aims at providing a pathology; a pathological reading meant to draw on the pre-colonial and colonial history without any presumptions so as to present the readers with possible alternative African discourses in future. His first novel Things Fall Apart can be taken as the best representative of such a penchant in Achebe. The present study seeks to approach Things Fall apart by reflecting on those discursive features which have provided the ground for constructing such a pathological reading and an alternative to the colonial discourse. To this end, some key terms introduced by Homi Bhabha and Mikhail Bakhtin such as ‘hybridity’, ‘otherness’ and ‘polyphony’, constitute the cornerstone of this study. Presumably, such an innovative reading of Achebe’s Things Fall Apart is to lead to a better understanding of his discourse and the efforts made by him to help the African readers figure out how to piece together what once fell apart; what they can rely on for building an independent future in the so-called postcolonial era