The effect of environment on the sustained load crack growth rates of forged WASPALOY

The sustained load crack growth rates of wrought WASPALOY* were measured in air and in high purity argon at 650 °C using single edge notched (SEN) and compact tension (CT) specimens machined out of a turbine disk. The crack growth rates measured in air exhibited great variability across the WASPALOY disk, while the crack growth rates measured in purified argon were of the same order of magnitude. This difference in crack growth rates is attributed to local variations in oxidation resistance at the tip of the growing crack. The density and the distribution of carbides in different locations of the WASPALOY disk accounts for the variability in crack growth resistance in air.     

Parents' informed consent decisions regarding psychotherapy for their children: Consideration of therapeutic risks and benefits.

Explores parents' use of informed consent information through an analog procedure in which parents were asked to make decisions regarding treatment. Three informed consent conditions with varying therapy risk and benefit information, and 2 case studies with different levels of child problem severity, were used. The effects of other variables, such as attitudes toward treatment and previous therapy experience, were also explored. Although the therapy risk and benefit information did not appear to influence the parents' decisions about entering treatment, child problem severity and parent attitude toward treatment were both positively associated with the likelihood of seeking treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

CONORBIT: constrained optimization by radial basis function interpolation in trust regions†

This paper presents CONORBIT (CONstrained Optimization by Radial Basis function Interpolation in Trust regions), a derivative-free algorithm for constrained black-box optimization where the objective and constraint functions are computationally expensive. CONORBIT employs a trust-region framework that uses interpolating radial basis function (RBF) models for the objective and constraint functions, and is an extension of the ORBIT algorithm [S.M. Wild, R.G. Regis and C.A. Shoemaker, ORBIT: optimization by radial basis function interpolation in trust-regions, SIAM J. Sci. Comput. 30 (2008), pp. 3197–3219]. It uses a small margin for the RBF constraint models to facilitate the generation of feasible iterates, and extensive numerical tests confirm that such a margin is helpful in improving performance. CONORBIT is compared with other algorithms on 27 test problems, a chemical process optimization problem, and an automotive application. Numerical results show that CONORBIT performs better than COBYLA (Powell 1994), a sequential penalty derivative-free method, an augmented Lagrangian method, a direct search method, and another RBF-based algorithm on the test problems and on the automotive application.     

Stochastic radial basis function algorithms for large-scale optimization involving expensive black-box objective and constraint functions

This paper presents a new algorithm for derivative-free optimization of expensive black-box objective functions subject to expensive black-box inequality constraints. The proposed algorithm, called ConstrLMSRBF, uses radial basis function (RBF) surrogate models and is an extension of the Local Metric Stochastic RBF (LMSRBF) algorithm by Regis and Shoemaker (2007a) [1] that can handle black-box inequality constraints. Previous algorithms for the optimization of expensive functions using surrogate models have mostly dealt with bound constrained problems where only the objective function is expensive, and so, the surrogate models are used to approximate the objective function only. In contrast, ConstrLMSRBF builds RBF surrogate models for the objective function and also for all the constraint functions in each iteration, and uses these RBF models to guide the selection of the next point where the objective and constraint functions will be evaluated. Computational results indicate that ConstrLMSRBF is better than alternative methods on 9 out of 14 test problems and on the MOPTA08 problem from the automotive industry (Jones, 2008 [2]). The MOPTA08 problem has 124 decision variables and 68 inequality constraints and is considered a large-scale problem in the area of expensive black-box optimization. The alternative methods include a Mesh Adaptive Direct Search (MADS) algorithm (Abramson and Audet, 2006 [3]; Audet and Dennis, 2006 [4]) that uses a kriging-based surrogate model, the Multistart LMSRBF algorithm by Regis and Shoemaker (2007a) [1] modified to handle black-box constraints via a penalty approach, a genetic algorithm, a pattern search algorithm, a sequential quadratic programming algorithm, and COBYLA (Powell, 1994 [5]), which is a derivative-free trust-region algorithm. Based on the results of this study, the results in Jones (2008) [2] and other approaches presented at the ISMP 2009 conference, ConstrLMSRBF appears to be among the best, if not the best, known algorithm for the MOPTA08 problem in the sense of providing the most improvement from an initial feasible solution within a very limited number of objective and constraint function evaluations.     

On the properties of positive spanning sets and positive bases

The concepts of positive span and positive basis are important in derivative-free optimization. In fact, a well-known result is that if the gradient of a continuously differentiable objective function on \(\mathbb{R}^n\) is nonzero at a point, then one of the vectors in any positive basis (or any positive spanning set) of \(\mathbb{R}^n\) is a descent direction for the objective function from that point. This article summarizes the basic results and explores additional properties of positive spanning sets, positively independent sets and positive bases that are potentially useful in the design of derivative-free optimization algorithms. In particular, it provides construction procedures for these special sets of vectors that were not previously mentioned in the literature. It also proves that invertible linear transformations preserve positive independence and the positive spanning property. Moreover, this article introduces the notion of linear equivalence between positive spanning sets and between positively independent sets to simplify the analysis of their structures. Linear equivalence turns out to be a generalization of the concept of structural equivalence between positive bases that was introduced by Coope and Price (SIAM J Optim 11:859–869, 2001). Furthermore, this article clarifies which properties of linearly independent sets, spanning sets and ordinary bases carry over to positively independent sets, positive spanning sets, and positive bases. For example, a linearly independent set can always be extended to a basis of a linear space but a positively independent set cannot always be extended to a positive basis. Also, the maximum size of a linearly independent set in \(R^n\) is n but there is no limit to the size of a positively independent set in \(\mathbb{R}^n\) when \(n \ge 3\). Whenever possible, the results are proved for the more general case of frames of convex cones instead of focusing only on positive bases of linear spaces. In addition, this article discusses some algorithms for determining whether a given set of vectors is positively independent or whether it positively spans a linear subspace of \(\mathbb{R}^n\). Finally, it provides an algorithm for extending any finite set of vectors to a positive spanning set of \(\mathbb{R}^n\) using only a relatively small number of additional vectors.     

A General Version of the Triple Π Operator

Recent developments of sensors and computers have raised the problem of handling huge amounts of complex data that users try to synthesize for decision making. Aggregation operators, such as those appearing in fuzzy sets theory, are useful tools for this synthesis but in their present formulation, these operators only deal with a finite set of arguments. In this paper, we introduce , an extension of both Yager–Rybalov Triple Π and Mean Triple Π operators to general measure spaces that can deal with temporal or spatiotemporal intensive data streams. Known properties and inequalities are extended in this more general setting. The notion of moving is also introduced and it can be applied to a solar radiation data stream. This may lead to further works on data fusion and on similar extensions of some other operators.     

AP1000 will meet the challenges of near-term deployment

The world demand for energy is growing rapidly, particularly in developing countries that are trying to raise the standard of living for billions of people, many of whom do not have access to electricity or clean water. Climate change and the concern for increased emissions of green house gases have brought into question the future primary reliance of fossil fuels. With the projected worldwide increase in energy demand, concern for the environmental impact of carbon emissions, and the recent price volatility of fossil fuels, nuclear energy is undergoing a rapid resurgence. This “nuclear renaissance” is broad based, reaching across Asia, North America, Europe, as well as selected countries in Africa and South America. Many countries have publicly expressed their intentions to pursue the construction of new nuclear energy plants. Some countries that have previously turned away from commercial nuclear energy are reconsidering the advisability of this decision. This renaissance is facilitated by the availability of more advanced reactor designs than are operating today, with improved safety, economy, and operations.One such design, the Westinghouse AP1000 advanced passive plant, has been a long time in the making! The development of this passive technology started over two decades ago from an embryonic belief that a new approach to design was needed to spawn a nuclear renaissance. The principal challenges were seen as ensuring reactor safety by requiring less reliance on operator actions and overcoming the high plant capital cost of nuclear energy. The AP1000 design is based on the use of innovative passive technology and modular construction, which require significantly less equipment and commodities that facilitate a more rapid construction schedule. Because Westinghouse had the vision and the perseverance to continue the development of this passive technology, the AP1000 design is ready to meet today's challenge of near-term deployment.     

Preparation and characteristics of new chiral photochromic copolymers

The copolymers consisting of chiral (S)-(−)-1-(4-nitrophenyl)pyrrolidin-2-yl]methyl 2-methacrylate ((S)-PYM) and azobenzene methacrylic co-monomers: 2-(methyl{4-[(E)-(5-methylisoxazol-3-yl)diazenyl]phenyl}amino)ethyl 2-methacrylate (ISM) or 2-{[4-[4-{(2,6-dimethylpirymidin-4-yl)amino]sulfonyl}phenyl) diazenyl]phenyl}-(methyl)amino]ethyl 2-methacrylate (SUM) were synthesized by radical polymerization. The quantum chemical calculations were carried out to predict spectral and nonlinear optical properties of the materials in question. The copolymers showed reversible photochromic properties under illumination with light by change of UV–vis spectra and ellipsometric parameters. The ellipsometric measurements made it possible to determine the change of refractive index under illumination that was in the range between 0.017 and 0.041 depending on copolymer type. Photochromic gratings were inscribed on the surface of polymer films in two kinds of experiments, leading to interesting conclusion that the surface relief grating could be recorded by two interfering laser beams as well as by a single linearly polarized laser beam. The chirooptical properties of the materials were investigated by circular dichroism spectroscopy.     

Highly porous PEM fuel cell cathodes based on low density carbon aerogels as Pt-support: Experimental study of the mass-transport losses

Carbon aerogels exhibiting high porous volumes and high surface areas, differentiated by their pore-size distributions were used as Pt-supports in the cathode catalytic layer of H₂/air-fed PEM fuel cell. The cathodes were tested as 50 cm² membrane electrode assemblies (MEAs). The porous structure of the synthesized catalytic layers was impacted by the nanostructure of the Pt-doped carbon aerogels (Pt/CAs). In this paper thus we present an experimental study aiming at establishing links between the porous structure of the cathode catalytic layers and the MEAs performances. For that purpose, the polarization curves of the MEAs were decomposed in 3 contributions: the kinetic loss, the ohmic loss and the mass-transport loss. We showed that the MEAs made with the different carbon aerogels had similar kinetic activities (low current density performance) but very different mass-transport voltage losses. It was found that the higher the pore-size of the initial carbon aerogel, the higher the mass-transport voltage losses. Supported by our porosimetry (N₂-adsorption and Hg-porosimetry) measurement, we interpret this apparent contradiction as the consequence of the more important Nafion penetration into the carbon aeorogel with larger pore-size. Indeed, the catalytic layers made from the larger pore-size carbon aerogel had lower porosities. We thus show in this work that carbon aerogels are materials with tailored nanostructured structure which can be used as model materials for experimentally testing the optimization of the PEM fuel cell catalytic layers.