Surface and porosity of nanocrystalline boehmite xerogels

Boehmite xerogels are prepared by hydrolysis of Al(OC4H9)3 followed by peptization with HNO3 (H+/Al = 0, 0.07, 0.2). XRD and TEM show that these gels are made of nanosized crystals (5–9 nm in width and 3 nm thick). According to the amount of acid, no significant differences are found in size and shape, but only in the spatial arrangement of the crystallites. Nitrogen adsorption–desorption isotherms of nonpeptized gels are of type IV, whereas isotherms of peptized gels are of type I. These isotherms are analyzed by the t-plot method. The majority of pore volume results from intercrystalline mesopores, but the peptized gels also contain intercrystalline micropores. The particle packing is very dense for the gel peptized with H+/Al = 0.2 (porosity = 0.26), but it is less dense in non-peptized gel (porosity = 0.44). Heating these gels under vacuum creates, from 250 °C onwards, an intracrystalline microporosity resulting from the conversion of boehmite into transition alumina. But heating also causes intercrystalline micropores collapsing. The specific surface area increases up to a limit temperature (300 °C for nonpeptized gels and 400 °C for peptized) beyond which sintering of the particles begins and the surface decreases. The PSD are calculated assuming a cylindrical pore geometry and using the corrected Kelvin equation proposed by Kruk et al. Peptized xerogels give a monomodal distribution with a maximum near 2 nm and no pores are larger than 6 nm. Nonpeptized gels have a bimodal distribution with a narrow peak near to 2 nm and a broad unsymmetrical peak with a maximum at 4 nm. Heating in air above 400 °C has a strong effect on the porosity. As the temperature increases, there is a broadening of the distribution and a marked decrease of small pores (below 3 nm). However, even after treatment at 800 °C, micropores are still present

On the Rationality of Escalation

Escalation is a typical feature of infinite games. Therefore tools conceived for studying infinite mathematical structures, namely those deriving from coinduction are essential. Here we use coinduction, or backward coinduction (to show its connection with the same concept for finite games) to study carefully and formally the infinite games especially those called dollar auctions, which are considered as the paradigm of escalation. Unlike what is commonly admitted, we show that, provided one assumes that the other agent will always stop, bidding is rational, because it results in a subgame perfect equilibrium. We show that this is not the only rational strategy profile (the only subgame perfect equilibrium). Indeed if an agent stops and will stop at every step, we claim that he is rational as well, if one admits that his opponent will never stop, because this corresponds to a subgame perfect equilibrium. Amazingly, in the infinite dollar auction game, the behavior in which both agents stop at each step is not a Nash equilibrium, hence is not a subgame perfect equilibrium, hence is not rational.Comment: 19 p. This paper is a duplicate of arXiv:1004.525

Training deep neural networks with low precision multiplications

Multipliers are the most space and power-hungry arithmetic operators of the digital implementation of deep neural networks. We train a set of state-of-the-art neural networks (Maxout networks) on three benchmark datasets: MNIST, CIFAR-10 and SVHN. They are trained with three distinct formats: floating point, fixed point and dynamic fixed point. For each of those datasets and for each of those formats, we assess the impact of the precision of the multiplications on the final error after training. We find that very low precision is sufficient not just for running trained networks but also for training them. For example, it is possible to train Maxout networks with 10 bits multiplications.Comment: 10 pages, 5 figures, Accepted as a workshop contribution at ICLR 201

BinaryConnect: Training Deep Neural Networks with binary weights during propagations

Deep Neural Networks (DNN) have achieved state-of-the-art results in a wide range of tasks, with the best results obtained with large training sets and large models. In the past, GPUs enabled these breakthroughs because of their greater computational speed. In the future, faster computation at both training and test time is likely to be crucial for further progress and for consumer applications on low-power devices. As a result, there is much interest in research and development of dedicated hardware for Deep Learning (DL). Binary weights, i.e., weights which are constrained to only two possible values (e.g. -1 or 1), would bring great benefits to specialized DL hardware by replacing many multiply-accumulate operations by simple accumulations, as multipliers are the most space and power-hungry components of the digital implementation of neural networks. We introduce BinaryConnect, a method which consists in training a DNN with binary weights during the forward and backward propagations, while retaining precision of the stored weights in which gradients are accumulated. Like other dropout schemes, we show that BinaryConnect acts as regularizer and we obtain near state-of-the-art results with BinaryConnect on the permutation-invariant MNIST, CIFAR-10 and SVHN.Comment: Accepted at NIPS 2015, 9 pages, 3 figure

The Effects of School Quality and Family Functioning on Youth Math Scores: a Canadian Longitudinal Analysis

This paper tries to disentangle the relative importance of family and school inputs on a child's cognitive achievement as measured by her percentile score on a mathematics test. We replicate a study by Todd and Wolpin (2007) in the United States with Canadian data. In contrast to their work that uses state-level indicators of school quality, we estimate our model with data from Statistics Canada's National Longitudinal Survey of Children and Youth (NLSCY) which provides micro-level information on the family and school history of the child. The sample used for the analysis is based on the 7- to 15-year-old longitudinal children who have completed at least two consecutive math tests. As in Todd and Wolpin, we conclude that cognitive outcomes are determined by current and past family inputs. Contrary to them, who find no impact of school inputs, we find that the quality of schools has a positive impact on achievement in mathematics.Math scores, human capital, child development, school and family inputs, panel data

Childcare Policy and Cognitive Outcomes of Children: Results from a Large Scale Quasi-Experiment on Universal Childcare in Canada

Effects of a low-fee universal childcare policy, initiated in Québec, the second most populous province in Canada, on the cognitive development of preschool children are estimated with a sample of 4- and 5-year-olds (N=8,875; N=17,154). In 1997, licensed and regulated providers of childcare services began offering daycare spaces at the reduced fee of $5 per day per child for children aged 4. By 2000, the low-fee policy applied to all children aged 0 to 59 months (not in kindergarten). The study uses 6 cycles of biennial data drawn from Statistics Canada's National Longitudinal Survey of Children and Youth (1994-2004) and quasi-experimental estimation methods to provide evidence that the policy had substantial negative effects on preschool children's Peabody Picture Vocabulary Test scores. The negative effects are found to be stronger for children with mothers who have lower levels of education.Preschool children, school readiness, childcare, kindergarten, treatment effects, natural experiment

Impact of Early Childhood Care and Education on Children's Preschool Cognitive Development: Canadian Results from a Large Quasi-experiment

On September 1st 1997, a new early childhood care and education policy was initiated by the provincial government of Québec, the second most populous province in Canada. Providers of childcare services licensed by the Department of the Family began offering daycare spaces at the reduced parental contribution of $5 per day per child for children aged 4. In successive years, the government reduced the age requirement and engaged in a plan to create new childcare facilities and pay for the cost of additional$5 per day childcare spaces. By September 2000, the low-fee policy applied to all children aged 0 to 59 months and the number of partly subsidized spaces increased from 77,000 in 1998 to 170,000 spaces, totally subsidized, by midyear 2003. In addition, on September 1st 1997, all public schools offered full-day rather than part-day kindergarten for 5-year-old children. No such important policy changes for preschool (including kindergarten) children were enacted in the other Canadian provinces over the years 1994 to 2003. Using biennial data drawn from Statistics Canada’s National Longitudinal Survey of Children and Youth (NLSCY), conducted since 1994-1995, this study attempts to estimate the effect of the policy on Québec’s preschool children cognitive test scores. A non-experimental evaluation framework based on multiple pre- and post-treatment periods is used to estimate the effect of the early childhood care and education regime on school readiness. The econometric results support the hypothesis that the policy had no effects on the cognitive development of 4-year-olds (the PPVT-R raw scores and the PPVT-R standardized scores). However, we provide evidence that the policy had a substantial negative impact on the scores of 5-year-olds.preschool children, school readiness, childcare, kindergarten, treatment effects, natural experiment

Catalytic coatings on stainless steel prepared by sol–gel route

Stainless steel (flat and microstructured) substrates have been coated with sol–gel catalysts made up of metal nanoparticles (Rh, Ni, Pt) dispersed on alumina and alumina–ceria supports. The aluminum monohydroxyde (boehmite) sols were synthesized by hot hydrolysis/peptization of an aluminum alkoxide (Yoldas method). It is shown that the rheological properties of the sol, especially the thixotropy, play a key role on the homogeneity and the quality of the film deposited on the metal substrate. The catalyst layers have a very good adhesion, a thickness which can be easily controlled (in the range 0.1 to 10 μm), a large specific surface area and a good mechanical and thermal stability

Modelo dominante y variaciones nacionales en el diseño de políticas de investigación en favor de la innovación tecnológica: una aproximación comparativa de los dispositivos de apoyo a la nanociencia y nanotecnología en Argentina y Francia

El objetivo de este texto es cuestionar el carácter global del proceso que conduce a la puesta en marcha de políticas de investigación en favor de la innovación tecnológica. Con dicha finalidad, el artículo realiza un análisis contrastivo de las políticas públicas en el campo de la nanociencia y nanotecnología en Argentina y Francia. Esta comparación muestra que, si bien las agendas y los instrumentos de políticas públicas de ciencia y tecnología se han globalizado, su puesta en marcha está fuertemente modelada por el contexto local en el que se desarrollan.Fil: Hubert, Matthieu Pierre. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes; Argentin