Effect of cerium concentration on corrosion resistance and polymerization of hybrid sol–gel coating on martensitic stainless steel

Stainless steels are increasingly used in the aeronautics field for the manufacture of structural parts. One of them, the X13VD martensitic stainless steel (X12CrNiMoV12-3), known for its good mechanical properties, has a poor corrosion resistance in confined or severe environments. In the past years, Cr(VI) based pre-treatments have been currently used for corrosion protection of different metals, however, they are toxic and due to environmental regulations, they will be definitely banned in a near future. Alternatives to replace Cr(VI) show advantages and drawbacks considering key properties such as: corrosion resistance, adhesion of coatings, fatigue resistance, durability and reliability. However, some of their possible alternatives show high potential.     

Comparison between the influence of applied electrode and electrolyte temperatures on porous anodizing of aluminium

A new approach for studying the effect of temperature on anodic oxide growth on aluminium is presented in this paper. Using an in-house developed electrode holder, anodizing is performed under conditions of applied and controlled electrode temperature. The influence of temperature on the process is evaluated by experiments in a broad temperature range for both the electrode and the electrolyte temperature. The electrochemical behaviour of the aluminium electrodes is demonstrated to be more susceptible to variations of the electrode temperature than to variations of the electrolyte temperature. Concerning the morphology of the anodic film it is shown that by cooling the electrode a normal oxide layer could be grown at high electrolyte temperatures, whereas anodizing in a cool electrolyte at high electrode temperature results in a collapsed porous structure at the oxide surface. Furthermore, the electrode temperature affects the formation ratio of the oxide to a larger extent than the electrolyte temperature, indicating its important influence even on the level of the ionic conductivity during anodic oxide growth. All observations indicate that merely considering the electrolyte temperature upon studying the influence of temperature on the process is not sufficient; the electrode temperature is much more determining.     

A Note on a Nonlinear Version of Wagner��s Classical Model of Internal Oxidation

A nonlinear version of Wagner??s classical model of internal oxidation is presented. This version accounts for the fact that precipitates may act as diffusion barriers by introducing a heuristic dependence of the diffusion coefficients of elements upon the local volume fraction of oxides formed. Remarkably, the now nonlinear problem still admits an analytic solution. This solution reveals a sudden and discontinuous transition from internal oxidation to formation of some external oxidized scale, when the fraction of oxide precipitates reaches some critical value which can be calculated explicitly in terms of the respective specific volumes of the matrix and the oxide.     

Driver–vehicle cooperation: a hierarchical cooperative control architecture for automated driving systems

The concept of automated driving changes the way humans interact with their cars. However, how humans should interact with automated driving systems remains an open question. Cooperation between a driver and an automated driving system—they exert control jointly to facilitate a common driving task for each other—is expected to be a promising interaction paradigm that can address human factors issues caused by driving automation. Nevertheless, the complex nature of automated driving functions makes it very challenging to apply the state-of-the-art frameworks of driver–vehicle cooperation to automated driving systems. To meet this challenge, we propose a hierarchical cooperative control architecture which is derived from the existing architectures of automated driving systems. Throughout this architecture, we discuss how to adapt system functions to realize different forms of cooperation in the framework of driver–vehicle cooperation. We also provide a case study to illustrate the use of this architecture in the design of a cooperative control system for automated driving. By examining the concepts behind this architecture, we highlight that the correspondence between several concepts of planning and control originated from the fields of robotics and automation and the ergonomic frameworks of human cognition and control offers a new opportunity for designing driver–vehicle cooperation.

     

LOcal Uncertainty Processing (LOUP) method for multidisciplinary robust design optimization

In this paper, we develop an easy-to-implement approximate method to take uncertainties into account during a multidisciplinary optimization. Multidisciplinary robust design usually involves setting up a full uncertainty propagation within the system, requiring major modifications in every discipline and on the shared variables. Uncertainty propagation is an expensive process, but robust solutions can be obtained more easily when the disciplines affected by uncertainties have a significant effect on the objectives of the problem. A heuristic method based on local uncertainty processing (LOUP) is presented here, allowing approximate solving of specific robust optimization problems with minor changes in the initial multidisciplinary system. Uncertainty is processed within the disciplines that it impacts directly, without propagation to the other disciplines. A criterion to verify a posteriori the applicability of the method to a given multidisciplinary system is provided. The LOUP method is applied to an aircraft preliminary design industrial test case, in which it allowed to obtain robust designs whose performance is more stable than the one of deterministic solutions, relatively to uncertain parameter variations.     

A formally verified hybrid system for safe advisories in the next-generation airborne collision avoidance system

The Next-Generation Airborne Collision Avoidance System (ACAS X) is intended to be installed on all large aircraft to give advice to pilots and prevent mid-air collisions with other aircraft. It is currently being developed by the Federal Aviation Administration (FAA). In this paper, we determine the geometric configurations under which the advice given by ACAS X is safe under a precise set of assumptions and formally verify these configurations using hybrid systems theorem proving techniques. We consider subsequent advisories and show how to adapt our formal verification to take them into account. We examine the current version of the real ACAS X system and discuss some cases where our safety theorem conflicts with the actual advisory given by that version, demonstrating how formal hybrid systems proving approaches are helping to ensure the safety of ACAS X. Our approach is general and could also be used to identify unsafe advice issued by other collision avoidance systems or confirm their safety.     

Dynamic Delaunay tetrahedralisation of a deforming surface

Reconstruction algorithms make it possible to retrieve a surface from the Delaunay tetrahedralisation (DT) of a point sampling, whose density reflects the surface local geometry and thickness. Most of these algorithms are static and some work remains to be done to handle deforming surfaces. In such case, we defend the idea that each point of the sampling should move with the surface using the information given by the motion to allow fast reconstruction. In this article, we tackle the problem of producing a good evolving sampling of a deforming surface S, and maintaining its DT along the motion. The surface is known only through a projection operator (O ₁):ℝ³→S, and a normal operator (O ₂) that returns the oriented normal at a point on the surface. On that basis, we offer some perspectives on how reconstruction algorithms can be extended to the tracking of deforming surfaces.     

Friable rock embedding in methyl methacrylate for thin-sectioning in geological preparations

In most cases, technical problems prevent the production of good geological thin-slabs from friable rocks such as muds, sands or decomposed granites. Usual impregnation methods using Araldite or epoxies lead to incompletely impregnated blocks. Furthermore the excessive heat occurring during polymerization alters the micromorphology of heat sensitive minerals. Methyl methacrylate (MMA) is a widely used plastic for bone embedding. We have developed a new procedure using vacuum infiltration with MMA in a cold environment. Wafers from friable rocks are easily obtained and can be processed in the same way as those of firm and coherent rocks, without grain loss nor mineral heat alterations.     

Regional characterization of freshwater Use in LCA: modeling direct impacts on human health

Life cycle assessment (LCA) is a methodology that quantifies potential environmental impacts for comparative purposes in a decision-making context. While potential environmental impacts from pollutant emissions into water are characterized in LCA, impacts from water unavailability are not yet fully quantified. Water use can make the resource unavailable to other users by displacement or quality degradation. A reduction in water availability to human users can potentially affect human health. If financial resources are available, there can be adaptations that may, in turn, shift the environmental burdens to other life cycle stages and impact categories. This paper proposes a model to evaluate these potential impacts in an LCA context. It considers the water that is withdrawn and released, its quality and scarcity in order to evaluate the loss of functionality associated with water uses. Regionalized results are presented for impacts on human health for two modeling approaches regarding affected users, including or not domestic uses, and expressed in disability-adjusted life years (DALY). A consumption and quality based scarcity indicator is also proposed as a midpoint. An illustrative example is presented for the production of corrugated board with different effluents, demonstrating the importance of considering quality, process effluents and the difference between the modeling approaches.