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Interval Analysis (interval + analysis)

Distribution by Scientific Domains
Medical Sciences28%

Selected Abstracts

An Optimizing Compiler for Automatic Shader Bounding

COMPUTER GRAPHICS FORUM, Issue 4 2010
Petrik Clarberg
Abstract Programmable shading provides artistic control over materials and geometry, but the black box nature of shaders makes some rendering optimizations difficult to apply. In many cases, it is desirable to compute bounds of shaders in order to speed up rendering. A bounding shader can be automatically derived from the original shader by a compiler using interval analysis, but creating optimized interval arithmetic code is non-trivial. A key insight in this paper is that shaders contain metadata that can be automatically extracted by the compiler using data flow analysis. We present a number of domain-specific optimizations that make the generated code faster, while computing the same bounds as before. This enables a wider use and opens up possibilities for more efficient rendering. Our results show that on average 42,44% of the shader instructions can be eliminated for a common use case: single-sided bounding shaders used in lightcuts and importance sampling. [source]

Guaranteed recursive non-linear state bounding using interval analysis

INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 3 2002
Michel Kieffer
Abstract The problem considered here is state estimation in the presence of unknown but bounded state perturbations and measurement noise. In this context, most available results are for linear models, and the purpose of the present paper is to deal with the non-linear case. Based on interval analysis and the notion of set inversion, a new state estimator is presented, which evaluates a set estimate guaranteed to contain all values of the state that are consistent with the available observations, given the perturbation and noise bounds and a set containing the initial value of the state. To the best of our knowledge, it is the first estimator for which this claim can be made. The precision of the set estimate can be improved, at the cost of more computation. Theoretical properties of the estimator are studied, and computer implementation receives special attention. A simple illustrative example is treated. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Deterministic global optimization of nonlinear dynamic systems

AICHE JOURNAL, Issue 4 2007
Youdong Lin
Abstract A new approach is described for the deterministic global optimization of dynamic systems, including optimal control problems. The method is based on interval analysis and Taylor models and employs a type of sequential approach. A key feature of the method is the use of a new validated solver for parametric ODEs, which is used to produce guaranteed bounds on the solutions of dynamic systems with interval-valued parameters. This is combined with a new technique for domain reduction based on the use of Taylor models in an efficient constraint propagation scheme. The result is that an ,-global optimum can be found with both mathematical and computational certainty. Computational studies on benchmark problems are presented showing that this new approach provides significant improvements in computational efficiency, well over an order of magnitude in most cases, relative to other recently described methods. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source]

Reliable computation of mixture critical points

AICHE JOURNAL, Issue 1 2001
Benito A. Stradi
The determination of critical points of mixtures is important for both practical and theoretical reasons in modeling phase behavior, especially at high pressure. This article presents the first completely reliable method for locating all the critical points of a given mixture. The method also verifies the nonexistence of a critical point if a mixture of a given composition does not have one. The methodology used is based on interval analysis, in particular an interval Newton/generalized bisection algorithm providing a mathematical and computational guarantee that all mixture critical points are located. The procedure is initialization-independent and thus requires no a priori knowledge of the number of mixture critical points or their approximate locations. The technique is illustrated using several example problems involving cubic equation-of-state models; however, the technique is for general purpose and can be applied in connection with other thermodynamic models. [source]

Is cytochrome P450 2C9 genotype associated with NSAID gastric ulceration?

BRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 6 2001
Jennifer H. Martin
Aims, The aim of this study was to explore whether genetic variation of cytochrome P450 2C9 (CYP2C9) contributes to NSAID-associated gastric ulceration. The hypothesis tested was that CYP2C9 poor metabolizer genotype would predict higher risk of gastric ulceration in patients on NSAIDs that are metabolized by CYP2C9, due to higher plasma NSAID concentrations. Methods, Peripheral blood DNA samples from 23 people with a history of gastric ulceration attributed to NSAIDs metabolized by CYP2C9, and from 32 people on NSAIDs without gastropathy, were analysed to determine CYP2C9 genotype. Results, The following genotypes were found: *1/*1 (wild type) in 70% of cases and 58% of controls, *1/*2 in 17% of cases and 29% of controls, *1/*3 in 13% of cases and 13% of controls. The difference between case and control nonwild-type genotype frequency was 11.5% (95% CI ,14,37%), with the direction of the difference being against the hypothesis. No individuals with homozygote poor metaboliser genotype were identified. The differences in genotype frequencies between the two groups were not significant and the frequencies were similar to those in a large published population study. Ninety-five percent binomial confidence interval analysis confirms that there is no apparent clinically significant relationship between CYP2C9 genotype and risk of gastric ulceration although a small difference in risk in poor metabolizers cannot be excluded. Conclusions, These results do not support the hypothesis that gastric ulceration resulting from NSAID usage is linked to the poor metabolizing genotypes of CYP2C9. [source]

Annual Scientific Meeting of ASCEPT, 1999 Careful Screening To Target Interventions To Prevent Sudden Cardiac Death

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 3 2001
Allan D Struthers
SUMMARY 1. Cardiac death is due not only to coronary artery disease, but also to left ventricular (LV) abnormalities (fibrosis, dysfunction) and arrhythmogenic triggers, such as autonomic imbalance. 2. Nitric oxide deficiency could be a key mediator leading not only to coronary atherosclerosis, but also to LV abnormalities and autonomic imbalance. 3. It may be possible to screen for the above abnormalities (e.g. echocardiography and brain natriuretic peptide levels for LV abnormalities, 24 h tapes for autonomic imbalance and QT interval analysis). 4. Once individuals are identified as being at high risk, a range of interventions is possible (e.g. intensive statin therapy or angiotensin-converting enzyme inhibitors if LV abnormalities or autonomic imbalance are found). [source]