Distributed timing analysis

As design complexities continue to grow larger, the need to efficiently analyze circuit timing with billions of transistors across multiple modes and corners is quickly becoming the major bottleneck to the overall chip design closure process. To alleviate the long runtimes, recent trends are driving the need of distributed timing analysis (DTA) in electronic design automation (EDA) tools. However, DTA has received little research attention so far and remains a critical problem. In this thesis, we introduce several methods to approach DTA problems. We present a near-optimal algorithm to speed up the path-based timing analysis in Chapter 1. Path-based timing analysis is a key step in the overall timing flow to reduce unwanted pessimism, for example, common path pessimism removal (CPPR). In Chapter 2, we introduce a MapReduce-based distributed Path-based timing analysis framework that can scale up to hundreds of machines. In Chapter 3, we introduce our standalone timer, OpenTimer, an open-source high-performance timing analysis tool for very large scale integration (VLSI) systems. OpenTimer efficiently supports (1) both block-based and path-based timing propagations, (2) CPPR, and (3) incremental timing. OpenTimer works on industry formats (e.g., .v, .spef, .lib, .sdc) and is designed to be parallel and portable. To further facilitate integration between timing and timing-driven optimizations, OpenTimer provides user-friendly application programming interface (API) for inactive analysis. Experimental results on industry benchmarks re- leased from TAU 2015 timing analysis contest have demonstrated remarkable results achieved by OpenTimer, especially in its order-of-magnitude speedup over existing timers. In Chapter 4 we present a DTA framework built on top of our standalone timer OpenTimer. We investigated into existing cluster computing frameworks from big data community and demonstrated DTA is a difficult fit here in terms of computation patterns and performance concern. Our specialized DTA framework supports (1) general design partitions (logical, physical, hierarchical, etc.) stored in a distributed file system, (2) non-blocking IO with event-driven programming for effective communication and computation overlap, and (3) an efficient messaging interface between application and network layers. The effectiveness and scalability of our framework has been evaluated on large hierarchical industry designs over a cluster with hundreds of machines. In Chapter 5, we present our system DtCraft, a distributed execution engine for compute-intensive applications. Motivated by our DTA framework, DtCraft introduces a high-level programming model that lets users without detailed experience of distributed computing utilize the cluster resources. The major goal is to simplify the coding efforts on building distributed applications based on our system. In contrast to existing data-parallel cluster computing frameworks, DtCraft targets on high-performance or compute- intensive applications including simulations, modeling, and most EDA applications. Users describe a program in terms of a sequential stream graph associated with computation units and data streams. The DtCraft runtime transparently deals with the concurrency controls including work distribution, process communication, and fault tolerance. We have evaluated DtCraft on both micro-benchmarks and large-scale simulation and optimization problems, and showed the promising performance from single multi-core machines to clusters of computers

Efficient Decision Support Systems

This series is directed to diverse managerial professionals who are leading the transformation of individual domains by using expert information and domain knowledge to drive decision support systems (DSSs). The series offers a broad range of subjects addressed in specific areas such as health care, business management, banking, agriculture, environmental improvement, natural resource and spatial management, aviation administration, and hybrid applications of information technology aimed to interdisciplinary issues. This book series is composed of three volumes: Volume 1 consists of general concepts and methodology of DSSs; Volume 2 consists of applications of DSSs in the biomedical domain; Volume 3 consists of hybrid applications of DSSs in multidisciplinary domains. The book is shaped upon decision support strategies in the new infrastructure that assists the readers in full use of the creative technology to manipulate input data and to transform information into useful decisions for decision makers

Coupled point neutron kinetics and thermal-hydraulics models of transient nuclear criticality excursions in wetted fissile uranium dioxide (UO2) powders

This thesis describes a phenomenologically based mathematical and computational methodology for the simulation of a postulated transient nuclear criticality excursion initiated by the incursion of water, from a fire-sprinkler system, into a bed of dry UO2 powder. These potentially hazardous multi-phase dispersed particulate systems may form as a result of a fire or explosion in a nuclear fuel fabrication facility. The models proposed in this thesis aim to support nuclear criticality safety analysis and assessment. In addition, the development of these models aims to support emergency planning and preparedness. The point neutron kinetics equations are coupled to phenomenological models of water infiltration, sedimentation, fluidisation, nuclear thermal hydraulics, radiolysis and boiling, through the use of multivariate reactivity feedback components. The spatial and temporal solution of this set of equations enables the modelling of postulated transient nuclear criticality excursions in highly dispersed three-phase particulate systems of UO2 powder. The results indicate that there is the potential for large positive reactivities to be added to a UO2 powder system as pores become filled with water. Generally, thermal expansion and Doppler broadening are insufficient to control the transient, leading to significant radiolysis and boiling on the surface of the UO2 powder particles. Radiolytic gas and steam bubble induced fluidisation and sedimentation significantly alters the characteristics of a transient nuclear criticality excursion and should be carefully considered. Research has also been undertaken examining transient nuclear criticality excursions in weak intrinsic neutron source UO2 powder systems by solving the forward probability balance equation and using a Gamma probability distribution function to estimate mean wait-time probability distributions. Significant variations in the potential initial peak power are predicted for highly enriched, wetted, UO2 powders as a function of the stochastic behaviour associated with criticality excursions in low neutron population systems.Open Acces

High-pressure states of bismuth

Bismuth is among the most studied of all elements, but its behaviour under pressure exhibits myriad unexpected puzzles even after many decades of research. Bismuth narrowly avoids being an insulator: a Peierls-type distortion almost completely gaps the electronic energy bands, producing a rhombohedral metal with a tiny overlap of conduction and valence bands. The resulting solitary free electron per 100,000 atoms can travel large distances in high-purity crystals, leading to a host of unusual properties. We show that the rhombohedral structure can be tuned with pressure, driving the carrier concentration to nearly zero. We compare our measurements to recent experimental advances implying the formation of novel electronic order driven by the pairing of low-density electrons and holes, and show evidence for a previously unseen phase at very low temperatures in the semiconducting state. We also present a method for calculating the carrier density and resistivity as a function of pressure, based on phenomenological band parameters and a simple charge-balance argument, and demonstrate that this approach can quite well describe most - but not all - of the observed behaviour of the resistivity. At higher pressures, bismuth undergoes a transition into a quasiperiodic host-guest structure. Here, two distinct crystal lattices coexist and interpenetrate, but the lattice parameters are incommensurate. This crystal thus lacks a single unit cell - an unexpected complexity for a simple element. The discovery of such unusual structures in elements is a new phenomenon and their physical properties are rather unexplored. We present experimental measurements of the resistivity and magnetic susceptibility in the incommensurate host-guest state. We argue that the experimental data (in particular, the shape of the normal-state electrical resistivity, and the high value of the low-temperature upper critical field) may be evidence for strong electron-phonon coupling. This strong coupling is consistent with theoretical predictions which suggest the presence of a low-energy phonon mode arising due to the vanishing energy cost of moving guest atoms through the host lattice.Sims fund scholarshi

A study of the high temperature superconductor YBa₂Cu₃O₇- and its cobalt-doped derivative

Static nuclear magnetic resonance (NMR) techniques have been used to study the magnetic hyperfine interactions of ⁶³Cu and ⁸⁹Y nuclei in the superconducting (T=1.5K) and normal (T=160-300K) states of the pure and cobalt doped Y-Ba-Cu-O layered cuprate systems. Sample quality and physical characteristics are well supported by magnetic susceptibility. Hall effect and X-ray diffraction measurements. We report ⁶³Cu NMR spin echo experiments, performed at 1.5K and 141MHz, on a uniaxially aligned sample of undoped YBa₂Cu₃O₇. By working at such low temperatures T, we provide clear confirmation that the spin components of the ⁶³Cu Knight shift, at both crystallographic sites and in all directions, vanish as T→0, leaving the orbital shift as the residual shift. This is indicative of singlet spin pairing in the superconducting state. The size and anisotropy of the ⁶³Cu(1,2) orbital shifts are consistent with a localised moment model in which there is a single hole of dₓ₂-[sub]y₂ (d[sub]y₂-[sub]z₂) symmetry in the d-shell shell of the Cu(2) (Cu(1)) ion. By working at high fields, where the demagnetisation corrections are much smaller, we are able to conclude that the disparity in the Kᶜorb(1,2) results from previous studies can be traced directly to discrepancies in the demagnetisation corrections, while inconsistencies in the Kᵃ, ᵇorb(1,2) components result from difficulties in analysing the restricted powder pattern. The effects of the atomic substitution of Co into the YBa₂(Cu₁-ₓMₓ)₃O₆.₉ (0≤x≤0.04) system have been investigated via an integrated ⁸⁹Y and ⁶³Cu NMR study on aligned powders. Combined susceptibility, X-ray and NMR measurements indicate that the Co ion substitutes preferentially at the Cu(1) site and bears a magnetic moment of around 3.7μB, consistent with a Co³⁺ localised moment of intermediate spin state (s=1). Theoretical modelling of the dipolar fields induced by such a moment suggest that the ⁸⁹Y and ⁶³Cu(2) NMR shifts and linewidths cannot be explained by a dipolar mechanism alone. The T[sub]c of the system is found to plateau at ~92K for x%0.5 is consistent with strong inhomogeneity in the Van Vleck component of the planes susceptibility. Finally, correlations between the ⁸⁹Y and ⁶³Cu(2) Knight shifts provide strong evidence in favour of a single quantum spin fluid

QUANTUM HARDWARE OF LIVING MATTER

This book belongs to a series of online books summarizing the recent state Topological Geometrodynamics (TGD) and its applications. TGD can be regarded as a unied theory of fundamental interactions but is not the kind of unied theory as so called GUTs constructed by graduate students at seventies and eighties using detailed recipes for how to reduce everything to group theory