52 research outputs found
Acoustic emission due to the interaction between shock and instability waves in 2D supersonic jet flows
An analytical model is developed to study the sound produced by the
interaction between shock and instability waves in two-dimensional supersonic
jet flows. The jet is considered to be of vortex-sheet type and 2D Euler
equations are linearised to determine the governing equations for shock,
instability waves, and their interaction. Pack's model is used to describe
shock waves, while instability waves are calculated using spatial stability
analysis. The interaction between shock and instability waves can be solved
analytically by performing Fourier transform and subsequently using the method
of steepest descent. Sound produced by the interaction between the instability
wave and a single shock cell is studied first, after which that due to a number
of cells follows. We find that the model developed in this study can correctly
predict the frequencies of the fundamental screech tone and its first and
second harmonics. We show that the predicted sound directivity, even from a
single shock cell, is in good agreement with experimental data. In particular,
this model shows the strongest noise emission close to the upstream direction
but the emitted noise starts to rapidly decay as the observer angle approaches
180 degrees, which is in accordance with experimental results; this suggests
that the effective noise from a single shock cell is far from of the monopole
type as assumed in the classical Powell's model. We find that the noise
directivity is very sensitive to the local growth rate of the instability waves
and the noise is generated primarily through the Mach wave mechanism.Comment: submitted to the Journal of Fluid Mechanic
Detect-and-forward relaying aided cooperative spatial modulation for wireless networks
A novel detect-and-forward (DeF) relaying aided cooperative SM scheme is proposed, which is capable of striking a flexible tradeoff in terms of the achievable bit error ratio (BER), complexity and unequal error protection (UEP). More specifically, SM is invoked at the source node (SN) and the information bit stream is divided into two different sets: the antenna index-bits (AI-bits) as well as the amplitude and phase modulation-bits (APM-bits). By exploiting the different importance of the AI-bits and the APM-bits in SM detection, we propose three low-complexity, yet powerful relay protocols, namely the partial, the hybrid and the hierarchical modulation (HM) based DeF relaying schemes. These schemes determine the most appropriate number of bits to be re-modulated by carefully considering their potential benefits and then assigning a specific modulation scheme for relaying the message. As a further benefit, the employment of multiple radio frequency (RF) chains and the requirement of tight inter-relay synchronization (IRS) can be avoided. Moreover, by exploiting the benefits of our low-complexity relaying protocols and our inter-element interference (IEI) model, a low-complexity maximum-likelihood (ML) detector is proposed for jointly detecting the signal received both via the source-destination (SD) and relay-destination (RD) links. Additionally, an upper bound of the BER is derived for our DeF-SM scheme. Our numerical results show that the bound is asymptotically tight in the high-SNR region and the proposed schemes provide beneficial system performance improvements compared to the conventional MIMO schemes in an identical cooperative scenario.<br/
Characterisation of electromagnetic compatibility drifts of nanoscale integrated circuit after accelerated life tests
2 pagesInternational audiencePresented is an original study about the effects of integrated circuit aging on electromagnetic emission and immunity to radio frequency interferences. For the first time an electromagnetic compatibility (EMC) qualification procedure is proposed to quantify the EMC level variation over the full lifetime of a component. Results presented show non-negligible variations of the emission and immunity thresholds after accelerated life tests, which could seriously deteriorate EMC margins required to ensure compliance with standard EMC levels
Ageing effect on electromagnetic susceptibility of a phase locked loop
5 pagesInternational audiencePhase locked loop in radiofrequency and mixed signal integrated circuit experience noise as electromagnetic interference coupled on input and power supply which translates to the timing jitter. Most of PLL noise analysis did not take into account the ageing effect. However device ageing can degrade the physical parameters of transistors and makes noise impact worse. This paper deals with the analyses of PLL immunity drift after accelerated ageing
Experimental verification of the usefulness of the nth power law MOSFET model under hot carrier wearout
4 pagesInternational audienceIn this paper the usefulness of the nth power law MOSFET model under Hot Carrier Injection (HCI) wearout has been experimentally demonstrated. In order to do that, three types of nFET transistors have been analyzed under different HCI conditions and the nth power law MOSFET model has been extracted for each sample. The results show that the model can reproduce the MOSFET behavior under HCI wearout mechanism. Therefore, the impact of HCI on circuits can be analyzed by using the nth power law MOSFET model
Epileptiform response of CA1 neurones to convulsant stimulation by cyclothiazide, kainic acid and pentylenetetrazol in anaesthetized rats
AbstractWe have previously reported that cyclothiazide (CTZ) evokes epileptiform activities in hippocampal neurons and induces seizure behavior. Here we further studied in vivo the sensitivity of the hippocampal CA1 neurons in response to CTZ in epileptogenesis in comparison with two other classic convulsants of kainic acid (KA) and pentylenetetrazol (PTZ).CTZ administered intracerebral ventricle (i.c.v.) induced epileptiform activities from an initial of multiple evoked population spikes, progressed to spontaneous spikes and finally to highly synchronized burst activities in hippocampal CA1 neurons. PTZ, when given by subcutaneously, but not by intracerebral ventricle injection, evoked similar progressive epileptiform activities. In contrast, KA given by i.c.v. induced a quick development of epileptiform burst activities and then shortly switched to continuous high frequency firing as acute status epilepticus (ASE). Pharmacologically, alprazolam, a high-potency benzodiazepine ligand, inhibited CTZ and PTZ, but not KA, induced epileptiform burst activities while GYKI 53784, an AMPA receptor antagonist, suppressed CTZ and KA but not PTZ evoked epileptiform activities.In conclusion, CTZ and PTZ induced epileptiform activities are most likely to share a similar progressive pattern in hippocampus with GABAergic mechanism dominant in epileptogenesis, while CTZ model involves additional glutamate receptor activation. KA induced seizure in hippocampus is different to that of both CTA and PTZ. The results from this study indicate that hippocampal neurons respond to various convulsant stimulation differently which may reflect the complicated causes of the seizure in clinics
Channel estimation in OFDM systems operating under high mobility using Wiener filter combined basis expansion model
Study of ageing effect on electromagnetic compatibility of integrated circuit
Avec la tendance continue vers la technologie nanomĂ©trique et l'augmentation des fonctions complexes intĂšgres dans les Ă©lectroniques systĂšmes embarquĂ©s, Assurant la compatibilitĂ© Ă©lectromagnĂ©tique (CEM) des systĂšmes Ă©lectroniques est un grand dĂ©fi. CEM est devenu une cause majeure de redesign des Circuits intĂšgres (CI). Dâailleurs, les performances des circuits pourraient ĂȘtre affectĂ©s par les mĂ©canismes de dĂ©gradation tels que hot carrier injection (HCI), negative bias temperature instability (NBTI), gate oxide breakdown, qui sont accĂ©lĂ©rĂ©s par les conditions d'exploitation extrĂȘme (haute / basse tempĂ©rature, surcharge Ă©lectrique, le rayonnement). Ce vieillissement naturel peut donc affecter les performances CEM des circuits intĂ©grĂ©s.Les travaux dĂ©veloppĂ©s dans notre laboratoire vise Ă clarifier le lien entre les dĂ©gradations induites par le vieillissement et les dĂ©rives CEM, de dĂ©velopper les modĂšles de prĂ©diction et de proposer des "insensibles au cours du temps" structures pour CEM protection, afin de fournir des mĂ©thodes et des guidelines aux concepteurs d'Ă©quipements et CI pour garantir la CEM au cours de durĂ©e de vie de leurs applications. Ce sujet de recherche est encore sous-explorĂ© en tant que communautĂ©s de recherche sur la «fiabilitĂ© IC» et «compatibilitĂ© Ă©lectromagnĂ©tique IC» nâa souvent pas de chevauchement.Ce manuscrit de thĂšse introduit une mĂ©thode pour quantifier l'effet du vieillissement sur les CEM des circuits intĂ©grĂ©s par la mesure et la simulation. Le premier chapitre donne un aperçu du contexte gĂ©nĂ©ral et le deuxiĂšme chapitre est dĂ©diĂ© a lâĂ©tat de l'art de CEM des circuits intĂ©grĂ©s et de problĂšmes de fiabilitĂ© IC. Les rĂ©sultats expĂ©rimentaux de circuits CEM Ă©volution sont prĂ©sentĂ©s dans le troisiĂšme chapitre. Ensuite, le quatriĂšme chapitre est consacrĂ© Ă la caractĂ©risation et la modĂ©lisation des mĂ©canismes de dĂ©gradation du CI. Un EMR modĂšle qui inclut l'Ă©lĂ©ment le vieillissement pour prĂ©dire la dĂ©rive du niveau CEM de notre puce de test aprĂšs stress est proposĂ©With the continuous trend towards nanoscale technology and increased integration of complex electronic functions in embedded systems, ensuring the electromagnetic compatibility (EMC) of electronic systems is a great challenge. EMC has become a major cause of IC redesign. Meanwhile, ICs performance could be affected by the degradation mechanisms such as hot carrier injection (HCI), negative bias temperature instability(NBTI), gate oxide breakdown, which are accelerated by the harsh operation conditions (high/low temperature, electrical overstress, radiation). This natural aging can thus affect EMC performances of ICs. The work developed in our laboratory aims at clarifying the link between ageing induced IC degradations and related EMC drifts, developing prediction models and proposing âtime insensitiveâ EMC protection structures, in order to provide methods and guidelines to IC and equipment designers to ensure EMC during lifetime of their applications. This research topic is still under-explored as research communities on âIC reliabilityâ and âIC electromagnetic compatibilityâ has often no overlap. The PhD manuscript introduced a methodology to quantify the effect of ageing on EMC of ICs by measurement and simulation. The first chapter gives an overview of the general context and the second chapter states the EMC of ICs state of the art and IC reliability issues. The experimental results of ICs EMC evolution are presented in the third chapter. Then, the fourth chapter is dedicated to the characterization and modeling IC degradation mechanism. An EMR model which includes the ageing element to predict our test chipâs EMC level drift after stress is propose
Adsorption Characteristics of Several Bioretention-Modified Fillers for Phosphorus
To optimize the bioretention mixed fillers with better removal of phosphorus, this paper studies the adsorption characteristics of single filler and modified mixed filler through static adsorption experiments, and adopts the dynamical mini-column experiments to examine the adsorption capacities of the soil and modified mixed fillers. Results show that, in the static adsorption experiments, both water treatment residual (WTR) and fly ash exhibit good adsorption capacity when used as a single filler and modifier. Adsorption capacity increases with increasing WTR and fly ash dosage in the mixed filler. The modified mixed filler with WTR exerts a clear effect in the dynamic adsorption experiment, which is unsaturated when influent phosphorus concentration is 1 mg/L and inflow amount is equivalent to 15 years of precipitation. The adsorption capacity of WTR is 3.5–4.5 times that of other mixed fillers. Fly ash as a modifier shows a poor dynamic adsorption effect and thus must be continuously studied. In this study, WTR is recommended as a bioretention phosphorus removal additive. In engineering applications, the amount of WTR added can be controlled within 5–10% (by mass) according to influent phosphorus concentration
Study of ageing effect on electromagnetic compatibility of integrated circuit
Avec la tendance continue vers la technologie nanomĂ©trique et l'augmentation des fonctions complexes intĂšgres dans les Ă©lectroniques systĂšmes embarquĂ©s, Assurant la compatibilitĂ© Ă©lectromagnĂ©tique (CEM) des systĂšmes Ă©lectroniques est un grand dĂ©fi. CEM est devenu une cause majeure de redesign des Circuits intĂšgres (CI). D ailleurs, les performances des circuits pourraient ĂȘtre affectĂ©s par les mĂ©canismes de dĂ©gradation tels que hot carrier injection (HCI), negative bias temperature instability (NBTI), gate oxide breakdown, qui sont accĂ©lĂ©rĂ©s par les conditions d'exploitation extrĂȘme (haute / basse tempĂ©rature, surcharge Ă©lectrique, le rayonnement). Ce vieillissement naturel peut donc affecter les performances CEM des circuits intĂ©grĂ©s.Les travaux dĂ©veloppĂ©s dans notre laboratoire vise Ă clarifier le lien entre les dĂ©gradations induites par le vieillissement et les dĂ©rives CEM, de dĂ©velopper les modĂšles de prĂ©diction et de proposer des "insensibles au cours du temps" structures pour CEM protection, afin de fournir des mĂ©thodes et des guidelines aux concepteurs d'Ă©quipements et CI pour garantir la CEM au cours de durĂ©e de vie de leurs applications. Ce sujet de recherche est encore sous-explorĂ© en tant que communautĂ©s de recherche sur la fiabilitĂ© IC et compatibilitĂ© Ă©lectromagnĂ©tique IC n a souvent pas de chevauchement.Ce manuscrit de thĂšse introduit une mĂ©thode pour quantifier l'effet du vieillissement sur les CEM des circuits intĂ©grĂ©s par la mesure et la simulation. Le premier chapitre donne un aperçu du contexte gĂ©nĂ©ral et le deuxiĂšme chapitre est dĂ©diĂ© a l Ă©tat de l'art de CEM des circuits intĂ©grĂ©s et de problĂšmes de fiabilitĂ© IC. Les rĂ©sultats expĂ©rimentaux de circuits CEM Ă©volution sont prĂ©sentĂ©s dans le troisiĂšme chapitre. Ensuite, le quatriĂšme chapitre est consacrĂ© Ă la caractĂ©risation et la modĂ©lisation des mĂ©canismes de dĂ©gradation du CI. Un EMR modĂšle qui inclut l'Ă©lĂ©ment le vieillissement pour prĂ©dire la dĂ©rive du niveau CEM de notre puce de test aprĂšs stress est proposĂ©With the continuous trend towards nanoscale technology and increased integration of complex electronic functions in embedded systems, ensuring the electromagnetic compatibility (EMC) of electronic systems is a great challenge. EMC has become a major cause of IC redesign. Meanwhile, ICs performance could be affected by the degradation mechanisms such as hot carrier injection (HCI), negative bias temperature instability(NBTI), gate oxide breakdown, which are accelerated by the harsh operation conditions (high/low temperature, electrical overstress, radiation). This natural aging can thus affect EMC performances of ICs. The work developed in our laboratory aims at clarifying the link between ageing induced IC degradations and related EMC drifts, developing prediction models and proposing time insensitive EMC protection structures, in order to provide methods and guidelines to IC and equipment designers to ensure EMC during lifetime of their applications. This research topic is still under-explored as research communities on IC reliability and IC electromagnetic compatibility has often no overlap. The PhD manuscript introduced a methodology to quantify the effect of ageing on EMC of ICs by measurement and simulation. The first chapter gives an overview of the general context and the second chapter states the EMC of ICs state of the art and IC reliability issues. The experimental results of ICs EMC evolution are presented in the third chapter. Then, the fourth chapter is dedicated to the characterization and modeling IC degradation mechanism. An EMR model which includes the ageing element to predict our test chip s EMC level drift after stress is proposedTOULOUSE-INSA-Bib. electronique (315559905) / SudocSudocFranceF
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