Self-Propagating High-Temperature Synthesis of Ti3SiC2: Study of the Reaction Mechanisms by Time-Resolved X-Ray Diffraction and Infrared Thermography

Ti₃SiC₂ is synthesized by self-propagating high-temperature synthesis (SHS) of elemental titanium, silicon, and graphite powders. The reaction paths and structure evolution are studied in situ during the SHS of the 3Ti+Si+2C mixture by time-resolved X-ray diffraction coupled with infrared thermography. The proposed reaction mechanism suggests that Ti₃SiC₂ might be formed from Ti–Si liquid phase and solid TiC _x . Finally, the effect of the powders starting composition on the Ti₃SiC₂ synthesis is studied. For the investigated initial mixtures, TiC _x is always formed as a major impurity together with the Ti₃SiC₂ phase.     

Formula One’s new urban economies

The Formula One (F1) industry has become a true microcosm of the world economy, as new business opportunities surface in emerging countries. Until the beginning of the twenty-first century, this sport was mostly relevant to traditional western urban elites, but since then, the F1 calendar has been largely altered to the benefit of ‘dominant-emerging cities’ and to the detriment of more traditional destinations. This article focuses on this urban question through a historical analysis of the F1 circuit’s expansion phases as well as through a study of the current Grand Prix’s estimate sanction fee.     

Model falsification diagnosis and sensor placement for leak detection in pressurized pipe networks

Pressurized pipe networks used for fresh-water distribution can take advantage of recent advances in sensing technologies and data-interpretation to evaluate their performance. In this paper, a leak-detection and a sensor placement methodology are proposed based on leak-scenario falsification. The approach includes modeling and measurement uncertainties during the leak detection process. The performance of the methodology proposed is tested on a full-scale water distribution network using simulated data. Findings indicate that when monitoring the flow velocity for 14 pipes over the entire network (295 pipes) leaks are circumscribed within a few potential locations. The case-study shows that a good detectability is expected for leaks of 50 L/min or more. A study of measurement configurations shows that smaller leak levels could also be detected if additional pipes are instrumented.     

Experimental comparison of classical PID and model-free control: Position control of a shape memory alloy active spring

Shape memory alloys (SMA) are being more frequently integrated into engineering applications. These materials with their shape memory effect enable the simplification of mechanisms and the reduction in size of actuators. SMA parts can easily be activated by Joule effect but their modeling and consequently their control remains difficult. It is principally due to their non-linear hysteretic thermomechanical behavior. Most of successful control strategies applied to SMA actuators are not often suitable for industrial applications: they are particularly heavy and use the Preisach model or neural networks to model the hysteretic behavior of these materials; this kind of model is difficult to identify and to use in real time. This paper deals with an application of the new framework of model-free control (MFC) of an SMA-spring based actuator. This control strategy relies on new results for fast derivative estimation of noisy signals. Their main advantages are: its simplicity and its robustness. Experimental results and comparisons with PI control are presented that demonstrate the efficiency of this new control strategy.     

A Simple Compressive Sensing Algorithm for Parallel Many-Core Architectures

In this paper we consider the l ¹-compressive sensing problem. We propose an algorithm specifically designed to take advantage of shared memory, vectorized, parallel and many-core microprocessors such as the Cell processor, new generation Graphics Processing Units (GPUs) and standard vectorized multi-core processors (e.g. quad-core CPUs). Besides its implementation is easy. We also give evidence of the efficiency of our approach and compare the algorithm on the three platforms, thus exhibiting pros and cons for each of them.     

Application of the Resources Model to the Supervision of an Automated Process

The present study was designed to ascertain how far flagging up potential errors can improve the automatic interpretation of technical documents. We used the resources model to analyze the supervised retro-conversion of architectural floor plans from the perspective of distributed cognition. Results showed that automated assistance helps users to correct errors spotted by the system and saves time. Surprisingly, they also showed that flagging up possible errors may make users less effective in identifying and correcting errors that go unnoticed by the system. Responses to a questionnaire probing the participants’ confidence in the system suggested that they were so trusting that they lowered their vigilance in those areas that had not been signaled by the system, leading to the identification of fewer errors there. Thus, although the participants’ confidence in the automated assistance system led to improved performances in those areas it highlighted, it also meant that areas to which the system did not draw attention were less thoroughly checked.     

Toward a Trust‐Based Construction Management

Abstract: The growing complexity of AEC projects is increasing the importance of the building construction coordination role. Moreover, the uncertainty linked to the environment of the construction activity makes way for the notion of trust. The coordinator can make use of multiple tools/views for accomplishing his mission. This research work suggests analyzing data coming from these different views to consolidate trust indicators informing the coordinator about “trust in the correct progression of the construction activity.” The approach suggested in this article distinguishes between four aspects of the activity determining the global trust level: task progress, actor's performance, documents required to perform the task, and building elements resulting from the task. The proposal suggests introducing these trust indicators in a dashboard, included in a multiview interface, thus allowing the coordinator to identify the tasks with a low trust level and to understand the nature of dysfunctions. A prototype has been developed and integrated in a service‐based IT infrastructure. Results of an experiment stage are finally discussed to validate the approach.     

Influence of surface tension, osmotic pressure and pores morphology on the densification of ice-templated ceramics

We attempt here to clarify the influence of the nature of the solvent on the ice-templating process, based on literature experimental results of porosity and suspension concentration. In particular, we compare the relative influence of surface tension, osmotic pressure and the pore size and radius of curvature on the densification of the green bodies. Variations of the osmotic pressure when changing the solvent can yield significantly different behaviour during the freezing stage and therefore significantly affect the densification behaviour, an effect not apparent when using the Shanti model. In addition, and equally important, a modification of the macropores morphology is induced by the evolution of the solvent crystals morphology, and resulting in smaller and more intricate crystals and macropores which facilitates the densification. The radius of curvature is probably also an essential parameter controlling the densification of ice-templated ceramics.     

Quantification of rotenone in seeds of different species of yam bean (Pachyrhizus sp.) by a SPE HPLC-UV method

This study describes the development of a validated method for the quantification of rotenone in yam bean. The milled seeds were submitted to a Soxhlet dichloromethane extraction which allowed extracting 90% of the seeds rotenone. Elimination of the lipids was obtained via solid phase extraction. Rotenone was eluted with dichloromethane/methanol and the solution dried under vacuum and solubilised directly in methanol before injection in HPLC. The whole process was realised as much as possible protected from light and at temperatures lower than 40 °C which allowed high recovery rates of spiked rotenone. Total error was used as criterion for the validation process and accuracy profiles drawn. The method allows the quantification of rotenone in yam bean seeds from 0.07% up to 1.25% (w/w). This method was applied to the quantification of rotenone in the seeds of several accessions of Pachyrhizus erosus and Pachyrhizus ahipa. The results range from 1.13 to 2.76 mg/g dry material.