1,619,660 research outputs found
PLRU Cache Domino Effects
Domino effects have been shown to hinder a tight prediction of worst case execution times (WCET) on real-time hardware. First investigated by Lundqvist and Stenström, domino effects caused by pipeline stalls were shows to exist in the PowerPC by Schneider. This paper extends the list of causes of domino effects by showing that the pseudo LRU (PLRU) cache replacement policy can cause unbounded effects on the WCET. PLRU is used in the PowerPC PPC755, which is widely used in embedded systems, and some x86 models
Numerical Modeling of AC Loss in HTS Coated Conductors and Roebel Cable Using T-A Formulation and Comparison with H Formulation
With recent advances in second-generation high temperature superconductors (2G HTS) and cable technologies, various numerical models based on finite-element method (FEM) have been proposed to help interpret measured AC loss and assist cable design. The T-A formulation, implemented in COMSOL, shows great potential for reducing the overall computation costs. In this paper, the performance of the T-A formulation for calculating the AC loss of coated superconductors and cables were assessed and compared against the widely accepted H formulation, with benchmark model of a single REBCO tape in 2D/3D and a 14-strand Roebel cable. Evaluation and comparison on key metrics including the computation time, the number of degrees of freedom and the numerical accuracy were presented, which could provide a reference for researchers in applying the T-A formulation for AC loss calculation
How The Timing of Grade Retention Affects Outcomes: Identification and Estimation of Time-Varying Treatment Effects
Increasingly, grade retention is viewed as an important alternative to social promotion, yet evidence to date is unable to disentangle how the effect of grade retention varies by abilities and over time. The key challenge is differential selection of students into retention across grades and by abilities. Because existing quasi-experimental methods cannot address this question, we develop a new strategy that is a hybrid between a control function and a generalization of the fixed effects approach. Applying our method to nationally-representative, longitudinal data, we find evidence of dynamic selection into retention and that the treatment effect of retention varies considerably across grades and unobservable abilities of students. Our strategy can be applied more broadly to many time-varying or multiple treatment settings.time-varying treatments, dynamic selection, grade retention, factor analysis
On Timing Model Extraction and Hierarchical Statistical Timing Analysis
In this paper, we investigate the challenges to apply Statistical Static
Timing Analysis (SSTA) in hierarchical design flow, where modules supplied by
IP vendors are used to hide design details for IP protection and to reduce the
complexity of design and verification. For the three basic circuit types,
combinational, flip-flop-based and latch-controlled, we propose methods to
extract timing models which contain interfacing as well as compressed internal
constraints. Using these compact timing models the runtime of full-chip timing
analysis can be reduced, while circuit details from IP vendors are not exposed.
We also propose a method to reconstruct the correlation between modules during
full-chip timing analysis. This correlation can not be incorporated into timing
models because it depends on the layout of the corresponding modules in the
chip. In addition, we investigate how to apply the extracted timing models with
the reconstructed correlation to evaluate the performance of the complete
design. Experiments demonstrate that using the extracted timing models and
reconstructed correlation full-chip timing analysis can be several times faster
than applying the flattened circuit directly, while the accuracy of statistical
timing analysis is still well maintained
Timing jitter of passively mode-locked semiconductor lasers subject to optical feedback; a semi-analytic approach
We propose a semi-analytical method of calculating the timing fluctuations in
mode-locked semiconductor lasers and apply it to study the effect of delayed
coherent optical feedback on pulse timing jitter in these lasers. The proposed
method greatly reduces computation times and therefore allows for the
investigation of the dependence of timing fluctuations over greater parameter
domains. We show that resonant feedback leads to a reduction in the timing
jitter and that a frequency-pulling region forms about the main resonances,
within which a timing jitter reduction is observed. The width of these
frequency-pulling regions increases linearly with short feedback delay times.
We derive an analytic expression for the timing jitter, which predicts a
monotonous decrease in the timing jitter for resonant feedback of increasing
delay lengths, when timing jitter effects are fully separated from amplitude
jitter effects. For long feedback cavities the decrease in timing jitter scales
approximately as with the increase of the feedback delay time
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