Review of Microstructure–Mechanical Property Relationships in Cast and Wrought Ni-Based Superalloys with Boron,Carbon, and Zirconium Microalloying Additions

Cast and wrought Ni-based superalloys are materials of choice for harsh high-temperature environments of aircraft engines and gas turbines. Their compositional complexity requires sophisticated thermo-mechanical processing. A typical microstructure consists of a polycrystalline γ-matrix, strengthening Ni₃(Al,Ti) γ′ precipitates, carbides (MC, M₆C, and M₂₃C₆), borides (M₂B, M₃B₂, and M₅B₃), and other inclusions. Microalloying additions of B, C, and Zr commonly improve high-temperature strength and creep resistance, although excessive additions are detrimental. Grain boundary (GB) segregation may improve cohesion and displace embrittling impurities. Finely dispersed carbides and borides are desired to control grain size via GB pinning. However, excessive decoration of GBs may lead to failure during processing and in-service. Hence, a systematic review on the roles of B, C, and Zr in cast and wrought Ni-based superalloys is required. The current state of knowledge on GB segregation and precipitation is reviewed. Experimental and modeling results are compared across various processing steps. The impact of GB precipitation on mechanical properties is most well researched. Co-precipitation in proximity to GBs interacting with local microstructure evolution and mechanical properties remains less explored. Addressing these gaps in knowledge allows a more complete understanding of processing–microstructure–properties relationships in advanced cast and wrought Ni-based superalloys.     

Interfacial Chemistry Effects in the Electrochemical Performance of Silicon Electrodes under Lithium-Ion Battery Conditions

Understanding the solid electrolyte interphase (SEI) formation and (de)lithiation phenomena at silicon (Si) electrodes is key to improving the performance and lifetime of Si-based lithium-ion batteries. However, these processes remain somewhat elusive, and, in particular, the role of Si surface termination merits further consideration. Here, scanning electrochemical cell microscopy (SECCM) is used in a glovebox, followed by secondary ion mass spectrometry (SIMS) at identical locations to study the local electrochemical behavior and associated SEI formation, comparing Si (100) with a native oxide layer (SiO_x/Si) and etched with hydrofluoric acid (HF-Si). HF-Si shows greater spatial electrochemical heterogeneity and inferior lithiation reversibility than SiO_x/Si. This is attributed to a weakly passivating SEI and irreversible lithium trapping at the Si surface. Combinatorial screening of charge/discharge cycling by SECCM with co-located SIMS reveals SEI chemistry as a function of depth. While the SEI thickness is relatively independent of the cycle number, the chemistry – particularly in the intermediate layers – depends on the number of cycles, revealing the SEI to be dynamic during cycling. This work serves as a foundation for the use of correlative SECCM/SIMS as a powerful approach to gain fundamental insights on complex battery processes at the nano- and microscales.     

Robust Kalman filtering for uncertain discrete‐time linear systems

This paper presents a steady‐state robust state estimator for a class of uncertain discrete‐time linear systems with norm‐bounded uncertainty. It is shown that if the system satisfies some particular structural conditions and if the uncertainty has a specific structure, the gain of the robust estimator (which assures a guaranteed cost) can be calculated using a formula only involving the original system matrices. Among the conditions the system has to satisfy, the strongest one relies on a minimum phase argument. It is also shown that under the assumptions considered, the robust estimator is in fact the Kalman filter for the nominal system. Copyright © 2003 John Wiley & Sons, Ltd.     

Robust stabilization and guaranteed cost control for discrete-time linear systems by static output feedback

This paper proposes a systematic approach for the static output feedback control design for discrete-time uncertain linear systems. It is shown that if the open-loop system satisfies some particular structural conditions and the uncertainty has a specific structure, a static output feedback gain can be calculated easily, using a formula only involving the original system matrices. Among the conditions the system has to satisfy, the strongest one relies on a minimum phase argument. Square and nonsquare systems are considered. The performance problem through a quadratic criterion is also discussed (guaranteed cost control).     

La numération de position : où en sont les connaissances d'élèves québécois?

RÉSUMÉ

La numération a fait l'objet d'études importantes, notamment au Québec, durant les années 1980–2000. Les études ont révélé sa complexité ainsi que les difficultés que posent à la fois son enseignement et son apprentissage. La présente étude s'inscrit dans le prolongement d'une suite d'études didactiques sur ces difficultés. Plus précisément, elle investigue les connaissances d'élèves québécois de 3^e année primaire sur la numération de position et les compare à celles d'une recherche phare menée par Bednarz et Dufour-Janvier dont les résultats ont fait l'objet de plusieurs publications (1982 Bednarz, N. et Dufour-Janvier, B. (1982). The understanding of numeration in primary school. Educational Studies in Mathematics, 13, 33–57. [Google Scholar], 1984a Bednarz, N. et Dufour-Janvier, B. (1984a). La numération: les difficultés suscitées par son apprentissage ; une stratégie didactique cherchant à favoriser une meilleure compréhension. Grand N, 33, 5–31. [Google Scholar], 1984b Bednarz, N. et Dufour-Janvier, B. (1984b). La numération: une stratégie didactique cherchant à favoriser une meilleure compréhension. Grand N, 34, 1–17. [Google Scholar], 1988 Bednarz, N. et Dufour-Janvier, B. (1988). A constructivist approach to numeration in primary school: Results of a three year intervention with the same group of children. Educational Studies in Mathematics, 19, 299–331. [Google Scholar]). Les résultats de notre étude montrent que si 30 ans ont passé depuis la recherche de Bednarz et Dufour-Janvier, peu de changements sont observés dans les conduites mathématiques des élèves en numération. Quelques hypothèses, relatives à la fois aux contraintes d'enseignement et aux difficultés spécifiques d'appropriation de la numération sont, au terme de l'article, formulées pour expliquer ces résultats.     

State of the Art in Hand and Finger Modeling and Animation

The human hand is a complex biological system able to perform numerous tasks with impressive accuracy and dexterity. Gestures furthermore play an important role in our daily interactions, and humans are particularly skilled at perceiving and interpreting detailed signals in communications. Creating believable hand motions for virtual characters is an important and challenging task. Many new methods have been proposed in the Computer Graphics community within the last years, and significant progress has been made towards creating convincing, detailed hand and finger motions. This state of the art report presents a review of the research in the area of hand and finger modeling and animation. Starting with the biological structure of the hand and its implications for how the hand moves, we discuss current methods in motion capturing hands, data‐driven and physics‐based algorithms to synthesize their motions, and techniques to make the appearance of the hand model surface more realistic. We then focus on areas in which detailed hand motions are crucial such as manipulation and communication. Our report concludes by describing emerging trends and applications for virtual hand animation.     

Gamification of Creativity: Exploring the Usefulness of Serious Games for Ideation

Organizing for idea generation is a recurring challenge in intensive innovation contexts. The literature on ideation has reached a compelling consensus on the features that such organizational devices must possess to support sufficient creativity: learning processes and a creative climate of confidence to promote collaboration. However, current practical methodologies struggle to simultaneously realize these two features. In this paper, we explore the potential of Serious Games, a collaborative tool that has been used since the 1960s to facilitate learning processes through the simulation of reality and a role‐playing game, to induce an immersive experience and, more recently, to support the ideation process. To do so, we conducted an exploratory case study using a Serious Game to support ideation in a French medium‐sized business. We then assess the strengths and areas for improvement of this Serious Game with respect to an ideation performance framework based on the existing literature. Our findings show that Serious Games are efficient tools for supporting existing knowledge exchange between participants and collaboration by providing a creative climate, but they may not sufficiently support learning of the external knowledge required to attain high levels of originality. Accordingly, we discuss some crucial parameters to be further explored to allow for the effective managerial use of such methodologies, such as the fine‐tuning of the knowledge content that serves as a basis for the game.     

A combined small- and wide-angle x-ray scattering detector for measurements on reactive systems

A detector with high dynamic range designed for combined small- and wide-angle x-ray scattering experiments has been developed. It allows measurements on single events and reactive systems, such as particle formation in flames and evaporation of levitating drops. The detector consists of 26 channels covering a region from 0.5° to 60° and it provides continuous monitoring of the sampled signal without readout dead time. The time resolution for fast single events is about 40 μs and for substances undergoing slower dynamics, the time resolution is set to 0.1 or 1 s with hours of continuous sampling. The detector has been used to measure soot particle formation in a flame, burning magnesium and evaporation of a toluene drop in a levitator. The results show that the detector can be used for many different applications with good outcomes and large potential.     

A Multi-formalism Approach for the Validation of UML Models

Our approach is based on UML models. They are edited with the rational Rose^™ tool [Rat96] and complemented with annotations that state several constraints. The class diagram is the starting point of a translation process that produces formal specifications in Z [Spi92] and Lustre [CHP87]. The RoZ tool is used to translate the class diagram into Z automatically. The Z and Lustre specifications are used to validate the UML models by means of a prover and a testing environment. Received February 2000 / Accepted in revised form December 2000     

The Psychology of Novelty‐Seeking,Creativity and Innovation: Neurocognitive Aspects Within a Work‐Psychological Perspective

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