Dye-Sensitized Solar Cell: nuova frontiera del fotovoltaico a basso costo

ope

Trapping and Reliability Investigations in GaN-based HEMTs

GaN-based high electron mobility transistors (HEMTs) are promising candidates for future microwave equipment, such as new solid state power amplifiers (SSPAs), thanks to their excellent performance. A first demonstration of GaN-MMIC transmitter has been developed and put on board the PROBA-V mission. But this technology still suffers from the trapping phenomena, principally due to lattice defects. Thus, the aim of this research is to investigate the trapping effects and the reliability aspects of the GH50 power transistors for C-band applications. A new trap investigation protocol to obtain a complete overview of trap behavior from DC to radio-frequency operation modes, based on combined pulsed I/V measurements, DC and RF drain current measurements, and low-frequency dispersion measurements, is proposed. Furthermore, a nonlinear electro-thermal AlGaN/GaN model with a new additive thermal-trap model including the dynamic behavior of these trap states and their associated temperature variations is presented, in order to correctly predict the RF performance during real RF operating conditions. Finally, an advanced time-domain methodology is presented in order to investigate the device’s reliability and to determine its safe operating area. This methodology is based on the continual monitoring of the RF waveforms and DC parameters under overdrive conditions in order to assess the degradation of the transistor characteristics in the RF power amplifier

Trapping and Reliability Investigations in GaN-based HEMTs

GaN-based high electron mobility transistors (HEMTs) are promising candidates for future microwave equipment, such as new solid state power amplifiers (SSPAs), thanks to their excellent performance. A first demonstration of GaN-MMIC transmitter has been developed and put on board the PROBA-V mission. But this technology still suffers from the trapping phenomena, principally due to lattice defects. Thus, the aim of this research is to investigate the trapping effects and the reliability aspects of the GH50 power transistors for C-band applications. A new trap investigation protocol to obtain a complete overview of trap behavior from DC to radio-frequency operation modes, based on combined pulsed I/V measurements, DC and RF drain current measurements, and low-frequency dispersion measurements, is proposed. Furthermore, a nonlinear electro-thermal AlGaN/GaN model with a new additive thermal-trap model including the dynamic behavior of these trap states and their associated temperature variations is presented, in order to correctly predict the RF performance during real RF operating conditions. Finally, an advanced time-domain methodology is presented in order to investigate the device’s reliability and to determine its safe operating area. This methodology is based on the continual monitoring of the RF waveforms and DC parameters under overdrive conditions in order to assess the degradation of the transistor characteristics in the RF power amplifier.I transistor ad effetto di campo ad alta mobilità elettronica (HEMTs) basati su nitruro di gallio (GaN) sono i più promettenti candidati, grazie alle loro eccellenti prestazioni per le future apparecchiature a microonde, per esempio gli amplificatori a stato solido (SSPA). Un primo dimostratore di circuito integrato monolitico a microonde (MMIC) in tecnologia GaN di un trasmettitore è stato sviluppato e messo a bordo della missione PROBA-V. Ma questa tecnologia soffre ancora dei fenomeni di intrappolamento, principalmente causati dai difetti presenti nel reticolo cristallino. Pertanto, lo scopo di questo dottorato è stato di investigare gli effetti di intrappolamento e gli aspetti di affidabilità dei transistor di potenza GH50 per le applicazioni a microonde in banda C. Viene proposto un nuovo protocollo di investigazione dei difetti per ottenere una panoramica completa del comportamento delle trappole dal funzionamento DC a quello radiofrequenza. Questo protocollo è basato sulle misure I / V impulsate, sulle misure del transiente della corrente di drain durante una eccitazione DC e RF e sulle misure della dispersione a bassa frequenza. Inoltre, viene presentato un modello elettro-termico non lineare del transistor GaN con un nuovo addizionale modello termico degli stati trappola. Questo ultimo include il comportamento dinamico e le loro relative variazioni in temperatura, al fine di prevedere correttamente le prestazioni RF durante le condizioni di funzionamento. Infine, viene presentata una metodologia avanzata nel dominio del tempo per indagare sull'affidabilità del dispositivo e per determinare la sua area operativa sicura. Questa metodologia si basa sul monitoraggio continuo delle forme d'onda RF e dei parametri DC in condizioni di overdrive, al fine di valutare la degradazione delle caratteristiche dei transistor nell'amplificatore di potenza RF

The stochastic neural network in VLSI for studying noise communication in crayfish

L'attivita neurale in natura presenta un andamento stocastico e gioca un ruolo significativo nel cervello. Tuttavia, la maggior parte degli articoli si limitano alla simulazione di neuroni stocastici. In questa tesi, proponiamo un nuovo modello stocastico secondo il formalismo di Hodgkin-Huxley basato su equazioni dierenziali stocastiche e moto browniano. Il nuovo modello di equazione dierenziale stocastiche riproduce una vasta gamma di dinamiche in modo piu realistico rispetto ai precedenti modelli deterministici. Tale modello stocastico e stato applicata a una semplice rete neurale che si trova sulla coda di un gambero chiamato CPR (caudal photoreceptor). Presentiamo una libreria di operatori analogici stocastici utilizzati per il calcolo analogico in tempo reale. Questa libreria permette di ottenere una implementazione in silicio della rete stocastica CPR che sarà collegata alle cellule nervose del gambero. L'interazione vivente-articiali permettera ai biologisti di comprendere meglio i fenomeni nervosi // The Neural activity in nature presents a stochastic trend and plays an important role in the brain. However, most papers are limited simulating stochastic neurons. In this thesis, we propose a novel stochastic model according to the Hodgkin{Huxley formalism using stochastic dierential equations and Brownian motion. The new stochastic dierential equation model reproduces a large range of dynamics more realistically than previous deterministic models. Such stochastic model has been applied to simple neural network that is located on the tail of the craysh called CPR (caudal photoreceptor). We present a library of stochastic analog operators used for the analog real-time computation. This library allows to obtain a silicon implementation of the CPR stochastic network that will be connected to the nerve cells of the craysh. The living-articial interaction will allow biologists to better understand the nervous phenomen

Investigation des effets de pièges et des aspects de fiabilité des transistors à haute mobilité d’électrons en Nitrure de Gallium

GaN-based high electron mobility transistors (HEMTs) are promising candidates for future microwave equipment, such as new solid state power amplifiers (SSPAs), thanks to their excellent performance. A first demonstration of GaN-MMIC transmitter has been developed and put on board the PROBA-V mission. But this technology still suffers from the trapping phenomena, principally due to lattice defects. Thus, the aim of this research is to investigate the trapping effects and the reliability aspects of the GH50 power transistors for C-band applications. A new trap investigation protocol to obtain a complete overview of trap behavior from DC to radio-frequency operation modes, based on combined pulsed I/V measurements, DC and RF drain current measurements, and low-frequency dispersion measurements, is proposed. Furthermore, a nonlinear electro-thermal AlGaN/GaN model with a new additive thermal-trap model including the dynamic behavior of these trap states and their associated temperature variations is presented, in order to correctly predict the RF performance during real RF operating conditions. Finally, an advanced time-domain methodology is presented in order to investigate the device’s reliability and to determine its safe operating area. This methodology is based on the continual monitoring of the RF waveforms and DC parameters under overdrive conditions in order to assess the degradation of the transistor characteristics in the RF power amplifier.Les transistors à haute mobilité d’électrons (HEMTs) en nitrure de gallium (GaN) s’affirment comme les candidats prometteurs pour les futurs équipements à micro-ondes - tels que les amplificateurs de puissance à état solide (SSPA), grâce à leurs excellentes performances. Une première démonstration d'émetteur en technologie GaN-MMIC a été développée et embarquée dans la mission spatiale PROBA-V. Mais cette technologie souffre encore des effets de pièges par des défauts présents au sein de la structure. L’objectif de ce travail est donc l'étude d’effets de pièges et des aspects de fiabilité des transistors de puissance GH50 pour des applications en bande C. Un protocole d’investigation des phénomènes de pièges est présenté, qui permet l’étude des dynamiques des effets de pièges du mode de fonctionnement DC au mode de fonctionnement radiofréquence, basé sur la combinaison des mesures IV impulsionnelles, des mesures de transitoires du courant de drain avec des impulsions DC et RF et des mesures de paramètres [S] en basse fréquence. Un modèle de HEMT AlGaN/GaN non-linéaire électrothermique est présenté, incluant un nouveau modèle thermique de pièges restituant le comportement dynamique de ces pièges et leurs variations en température afin de prédire correctement les performances en conditions réelles de fonctionnement RF. Enfin, une méthodologie temporelle pour l’évaluation de la fiabilité et de limites réelles d'utilisation de transistors dans l'amplificateur de puissance RF en régime d’overdrive (très forte compression), basée sur la mesure monitorée de Formes d'Onde Temporelles (FOT), est proposée

Metabolic abnormalities associated with initiation of systemic treatment for psoriasis: evidence from the Italian Psocare Registry.

NCBINCBI Logo Skip to main content Skip to navigation Resources How To About NCBI Accesskeys Sign in to NCBI PubMed US National Library of Medicine National Institutes of Health Search database Search term Clear input Advanced Help Result Filters Display Settings: Abstract Send to: J Eur Acad Dermatol Venereol. 2013 Jan;27(1):e30-41. doi: 10.1111/j.1468-3083.2012.04450.x. Epub 2012 Feb 7. Metabolic abnormalities associated with initiation of systemic treatment for psoriasis: evidence from the Italian Psocare Registry. Gisondi P1, Cazzaniga S, Chimenti S, Giannetti A, Maccarone M, Picardo M, Girolomoni G, Naldi L; Psocare Study Group. Collaborators (368) Author information Abstract OBJECTIVE: To evaluate variations in laboratory parameters and diagnoses of selected clinical conditions up to 16 weeks after starting a new systemic psoriasis treatment for Psocare Registry enrollees. DESIGN: Prospective cohort study. SETTING: Italian public referral centres for psoriasis treatment. PATIENTS: First-time recipients (n = 10,539) of continuous systemic psoriasis treatment for at least 16 weeks. MAIN OUTCOME MEASURE: Mean variations in (weeks 8 and 16) and proportions of patients reaching a clinically meaningful increase in serum levels (week 16) of total and low-density lipoprotein cholesterol, triglycerides, aspartate amino transferase, alanine amino transferase and creatinine, as well as week-16 cumulative incidences of new diagnoses of diabetes mellitus and arterial hypertension. RESULTS: Mean cholesterol and triglyceride levels significantly increased in patients treated with acitretin or cyclosporine. Mean triglyceride levels also increased in efalizumab- and etanercept-treated patients. Mean transaminase values increased in methotrexate-treated patients, and mean aspartate amino transferase levels increased in infliximab-treated patients. The average serum creatinine value increased in cyclosporine-treated patients. Acitretin and cyclosporine were associated with risk of hypercholesterolaemia (odds ratios 1.51 and 1.34) and acitretin with risk of hypertriglyceridaemia (odds ratio 1.43). Methotrexate and infliximab were associated with risk of more than doubling the upper normal aspartate amino transferase (odds ratios 2.06 and 1.87) and alanine amino transferase (odds ratios 2.38 and 1.74) values. The relative risk of developing arterial hypertension and diabetes was increased for patients receiving cyclosporine (odds ratios 3.31 and 2.88). CONCLUSION: Systemic treatments for psoriasis resulted in heterogeneous effects on the parameters analysed