56 research outputs found
Fast and accurate SER estimation for large combinational blocks in early stages of the design
Soft Error Rate (SER) estimation is an important challenge for integrated circuits because of the increased vulnerability brought by technology scaling. This paper presents a methodology to estimate in early stages of the design the susceptibility of combinational circuits to particle strikes. In the core of the framework lies MASkIt , a novel approach that combines signal probabilities with technology characterization to swiftly compute the logical, electrical, and timing masking effects of the circuit under study taking into account all input combinations and pulse widths at once. Signal probabilities are estimated applying a new hybrid approach that integrates heuristics along with selective simulation of reconvergent subnetworks. The experimental results validate our proposed technique, showing a speedup of two orders of magnitude in comparison with traditional fault injection estimation with an average estimation error of 5 percent. Finally, we analyze the vulnerability of the Decoder, Scheduler, ALU, and FPU of an out-of-order, superscalar processor design.This work has been partially supported by the Spanish Ministry of Economy and Competitiveness and Feder Funds under grant TIN2013-44375-R, by the Generalitat de Catalunya under grant FI-DGR 2016, and by the FP7 program of the EU under contract FP7-611404 (CLERECO).Peer ReviewedPostprint (author's final draft
Dynamical Instabilities and High Temperature Phase Stability in Ionic Crystals.
A large class of high-temperature phases become dynamically unstable at low temperatures and transform to lower symmetry phases upon cooling. In this thesis we seek to understand the energetics and vibrational thermodynamic properties associated with these transformation mechanisms in a variety of technologically important materials, including a newly discovered battery solid electrolyte, oxide phases in nuclear rod cladding, and thermal barrier coatings.
Using first-principles phonon calculations, we examine the dynamical stability and vibrational properties of Li3OCl, a solid electrolyte material. We show that it is dynamically unstable with respect to octahedral rotations. Further examination of the anharmonic energy landscapes resulting from these rotations revealed that while rotations can lead to lower symmetry structures, the energy gained by these rotations are small. At low temperatures, the cubic form should persist due to anharmonic vibrational excitations. We also find that Li3OCl is entropically stabilized with respect to LiCl and Li2O at temperatures above 480
K.
Zirconium alloys used in nuclear fuel rod cladding experience corrosive and oxidizing environments. Understanding the phase stability of these oxide phases at high temperatures is crucial to designing corrosion-resistant materials. Vibrational free energies for several Zr-O compounds were calculated and incorporated into a previously calculated temperature composition phase diagram [1] to identify the temperature stability limit of the recently identified delta-prime-ZrO phase. We show that this phase is stable well beyond typical nuclear reactor temperatures.
Instabilities observed in cubic, tetragonal, and monoclinic ZrO2 are also studied. The cubic instability leads to a transformation into the tetragonal phase. A volume-induced instability in the tetragonal phase results in a transformation into a new orthorhombic phase. This instability has implications for the finite temperature stability of tetragonal ZrO2 and the role of anharmonicity in high-temperature materials. Strain is shown to affect stabilities of the three tetragonal variants, as well as the relative stabilities of the tetragonal and monoclinic phases. These results suggest that strain can stabilize the high-temperature tetragonal phase, which is preferable for epitaxial thin films used in high-k dielectrics and for ferroelastic toughening in thermal barrier coatings.PhDMaterials Science and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/116700/1/mhichen_1.pd
Phonons and related properties of extended systems from density-functional perturbation theory
This article reviews the current status of lattice-dynamical calculations in
crystals, using density-functional perturbation theory, with emphasis on the
plane-wave pseudo-potential method. Several specialized topics are treated,
including the implementation for metals, the calculation of the response to
macroscopic electric fields and their relevance to long wave-length vibrations
in polar materials, the response to strain deformations, and higher-order
responses. The success of this methodology is demonstrated with a number of
applications existing in the literature.Comment: 52 pages, 14 figures, submitted to Review of Modern Physic
Multilevel Modeling, Formal Analysis, and Characterization of Single Event Transients Propagation in Digital Systems
RÉSUMÉ La croissance exponentielle du nombre de transistors par puce a apporté des progrès considérables
aux performances et fonctionnalités des dispositifs semi-conducteurs avec une miniaturisation des dimensions physiques ainsi qu’une augmentation de vitesse. De nos jours, les appareils électroniques utilisés dans un large éventail d’applications telles que les systèmes
de divertissement personnels, l’industrie automobile, les systèmes électroniques médicaux, et le secteur financier ont changé notre façon de vivre. Cependant, des études récentes ont démontré que le rétrécissement permanent de la taille des transistors qui s’approchent des dimensions
nanométriques fait surgir des défis majeurs. La réduction de la fiabilité au sens large (c.-à -d., la capacité à fournir la fonction attendue) est l’un d’entre eux. Lorsqu’un système est conçu avec une technologie avancée, on s’attend à ce qu’ il connaît plus de défaillances
dans sa durée de vie. De telles défaillances peuvent avoir des conséquences graves allant des pertes financières aux pertes humaines. Les erreurs douces induites par la radiation, qui sont apparues d’abord comme une source de
panne plutôt exotique causant des anomalies dans les satellites, sont devenues l’un des problèmes
les plus difficiles qui influencent la fiabilité des systèmes microélectroniques modernes, y compris les dispositifs terrestres. Dans le secteur médical par exemple, les erreurs douces ont été responsables de l’échec et du rappel de plusieurs stimulateurs cardiaques implantables. En fonction du transistor affecté lors de la fabrication, le passage d’une particule peut induire
des perturbations isolées qui se manifestent comme un basculement du contenu d’une cellule de mémoire (c.-à -d., Single Event Upsets (SEU)) ou un changement temporaire de la
sortie (sous forme de bruit) dans la logique combinatoire (c.-à -d., Single Event Transients (SETs)). Les SEU ont été largement étudiés au cours des trois dernières décennies, car ils étaient considérés comme la cause principale des erreurs douces. Néanmoins, des études expérimentales
ont montré qu’avec plus de miniaturisation technologique, la contribution des SET au taux d’erreurs douces est remarquable et qu’elle peut même dépasser celui des SEU
dans les systèmes à haute fréquence [1], [2]. Afin de minimiser l’impact des erreurs douces, l’effet des SET doit être modélisé, prédit et atténué. Toutefois, malgré les progrès considérables accomplis dans la vérification fonctionnelle des circuits numériques, il y a eu très peu
de progrès en matià re de vérification non-fonctionnelle (par exemple, l’analyse des erreurs douces). Ceci est dû au fait que la modélisation et l’analyse des propriétés non-fonctionnelles des SET pose un grand défi. Cela est lié à la nature aléatoire des défauts et à la difficulté
de modéliser la variation de leurs caractéristiques lorsqu’ils se propagent.----------ABSTRACT
The exponential growth in the number of transistors per chip brought tremendous progress in the performance and the functionality of semiconductor devices associated with reduced physical dimensions and higher speed. Electronic devices used in a wide range of applications
such as personal entertainment systems, automotive industry, medical electronic systems, and financial sector changed the way we live nowadays. However, recent studies reveal that further downscaling of the transistor size at nano-scale technology leads to major challenges.
Reliability (i.e., ability to provide intended functionality) is one of them, where a system
designed in nano-scale nodes is expected to experience more failures in its lifetime than if it was designed using larger technology node size. Such failures can lead to serious conséquences ranging from financial losses to even loss of human life. Soft errors induced by radiation,
which were initially considered as a rather exotic failure mechanism causing anomalies in satellites, have become one of the most challenging issues that impact the reliability of modern microelectronic systems, including devices at terrestrial altitudes. For instance, in the medical
industry, soft errors have been responsible of the failure and recall of many implantable cardiac pacemakers.
Depending on the affected transistor in the design, a particle strike can manifest as a bit flip in a state element (i.e., Single Event Upset (SEU)) or temporally change the output of a combinational gate (i.e., Single Event Transients (SETs)). Initially, SEUs have been widely
studied over the last three decades as they were considered to be the main source of soft errors. However, recent experiments show that with further technology downscaling, the contribution of SETs to the overall soft error rate is remarkable and in high frequency systems, it might
exceed that of SEUs [1], [2]. In order to minimize the impact of soft errors, the impact of SETs needs to be modeled, predicted, and mitigated. However, despite considerable progress towards developing efficient methodologies for the functional verification of digital designs, advances in non-functional verification (e.g., soft error analysis) have been lagging. This
is due to the fact that the modeling and analysis of non-functional properties related to SETs is very challenging. This can be related to the random nature of these faults and the difficulty of modeling the variation in its characteristics while propagating. Moreover, many
details about the design structure and the SETs characteristics may not be available at high
abstraction levels. Thus, in high level analysis, many assumptions about the SETs behavior are usually made, which impacts the accuracy of the generated results. Consequently, the lowcost detection of soft errors due to SETs is very challenging and requires more sophisticated
techniques
Reliability-energy-performance optimisation in combinational circuits in presence of soft errors
PhD ThesisThe reliability metric has a direct relationship to the amount of value produced
by a circuit, similar to the performance metric. With advances in CMOS
technology, digital circuits become increasingly more susceptible to soft errors.
Therefore, it is imperative to be able to assess and improve the level of reliability
of these circuits. A framework for evaluating and improving the reliability of
combinational circuits is proposed, and an interplay between the metrics of
reliability, energy and performance is explored.
Reliability evaluation is divided into two levels of characterisation: stochastic
fault model (SFM) of the component library and a design-specific critical vector
model (CVM). The SFM captures the properties of components with regard to
the interference which causes error. The CVM is derived from a limited number
of simulation runs on the specific design at the design time and producing
the reliability metric. The idea is to move the high-complexity problem of the
stochastic characterisation of components to the generic part of the design
process, and to do it just once for a large number of specific designs. The
method is demonstrated on a range of circuits with various structures.
A three-way trade-off between reliability, energy, and performance has
been discovered; this trade-off facilitates optimisations of circuits and their
operating conditions.
A technique for improving the reliability of a circuit is proposed, based on
adding a slow stage at the primary output. Slow stages have the ability to
absorb narrow glitches from prior stages, thus reducing the error probability.
Such stages, or filters, suppress most of the glitches generated in prior stages
and prevent them from arriving at the primary output of the circuit. Two filter
solutions have been developed and analysed. The results show a dramatic
improvement in reliability at the expense of minor performance and energy
penalties.
To alleviate the problem of the time-consuming analogue simulations involved in the proposed method, a simplification technique is proposed. This
technique exploits the equivalence between the properties of the gates within
a path and the equivalence between paths. On the basis of these equivalences,
it is possible to reduce the number of simulation runs. The effectiveness of
the proposed technique is evaluated by applying it to different circuits with
a representative variety of path topologies. The results show a significant
decrease in the time taken to estimate reliability at the expense of a minor
decrease in the accuracy of estimation. The simplification technique enables
the use of the proposed method in applications with complex circuits.Ministry of Education and Scientific Research in Liby
Novel methods for treatment planning in Ion Beam Therapy
One of the biggest challenges in ion beam therapy is the mitigation of the impact of uncertainties in the quality of treatment plans. Some of the strategies used to reduce this impact are based on concepts developed decades ago for photon therapy. In this thesis novel methods and concepts, tailored to the specifi c needs of ion beam therapy, are proposed which reduce the effect of uncertainties on treatment plans. This is done in two steps: First, we revisit the concept of the Planning Target Volume and propose a novel method for its de nition. This method enhances robustness of treatment plans and reduces the amount of healthy tissue irradiated. In a clinical situation this could translate into an enhancement of the tumor control probability while reducing side e ects. The concept of robust conformity (conformity in the presence of uncertainties) is proposed along with a way to quantify it. Secondly,a method to select robust beam angle con gurations that also spare organs at risks is proposed. This combination is a new conceptual layout to tackle the challenges of ion beam therapy and enhances its potential
Cone Penetration Testing 2022
This volume contains the proceedings of the 5th International Symposium on Cone Penetration Testing (CPT’22), held in Bologna, Italy, 8-10 June 2022. More than 500 authors - academics, researchers, practitioners and manufacturers – contributed to the peer-reviewed papers included in this book, which includes three keynote lectures, four invited lectures and 169 technical papers. The contributions provide a full picture of the current knowledge and major trends in CPT research and development, with respect to innovations in instrumentation, latest advances in data interpretation, and emerging fields of CPT application. The paper topics encompass three well-established topic categories typically addressed in CPT events: - Equipment and Procedures - Data Interpretation - Applications. Emphasis is placed on the use of statistical approaches and innovative numerical strategies for CPT data interpretation, liquefaction studies, application of CPT to offshore engineering, comparative studies between CPT and other in-situ tests. Cone Penetration Testing 2022 contains a wealth of information that could be useful for researchers, practitioners and all those working in the broad and dynamic field of cone penetration testing
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