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.     

Determination of the Mg-Rich Phase Boundary of the Binary Mg-Nd Phase Diagram by Means of Atom Probe Tomography

The present paper relates the investigation of the Mg-rich side of the binary Mg-Nd phase diagram by means of Atom Probe Tomography (APT). The solid solubility of Nd in Mg at the temperatures 400, 480, 520 °C has been measured. The results of the current investigation demonstrate that the solid solubility of Nd in Mg is much larger than is usually supposed and presented in more recent Mg-Nd phase diagrams. The data presented in this work can be used for further thermodynamic calculations in order to interpolate the phase boundary between temperature points.     

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.     

Characterisation of power modules ceramic substrates for reliability aspects

Electronic power devices used for transportation applications (automotive and avionics) experience severe temperature variations which promote their thermal fatigue and failure. For example, for power modules mounted on the engine of an aircraft, temperature variations range from −55 °C (in the worst case of storage before takeoff) to +200 °C (flight). In theses conditions failure (conchoïdal fracture) can occur in DBC substrates. The Weibull approach was used to model the brittle fracture of the ceramic layer from a natural defect. Besides, geometric singularities in the upper ceramic/copper interface are at the origin of cracks, which grow by fatigue and finally bifurcate and break the ceramic layer. With the framework of linear elastic fracture mechanics (LEFM) and using the finite element method, it was possible to analyse how a thermal loading history may modify the risk of failure of the DBC substrate and can increase the fatigue life of a power module. This result shows that the fatigue life and the reliability of power electronic devices could be optimized using a thermo-mechanical approach of the problem and suitable failure criteria.     

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.     

Effect of the oxygen content in solution on the static and cyclic deformation of titanium foams

It is well known that interstitials affect the mechanical properties of titanium and titanium alloys. Their effects on the fatigue properties of titanium foams have not, however, been documented in the literature. This paper presents the effect of the oxygen content on the static and dynamic compression properties of titanium foams. Increasing the oxygen content from 0.24 to 0.51 wt% O in solution significantly increases the yield strength and reduces the ductility of the foams. However, the fatigue limit is not significantly affected by the oxygen content and falls within the 92 MPa ± 12 MPa range for all specimens investigated in this study. During cyclic loading, deformation is initially coming from cumulative creep followed by the formation of microcracks. The coalescence of these microcracks is responsible for the rupture of the specimens. Fracture surfaces of the specimens having lower oxygen content show a more ductile aspect than the specimens having higher oxygen content.     

Recruitment and training of a sensory expert panel to measure the touch of beverage packages: Issue and methods employed

Although formerly considered an intermediate product, packaging has become a main component of the product and largely contributes to its perceived quality. It is the first contact with consumer. For many years, the food industry has used sensory analysis techniques to improve the gustative and olfactive quality of its products, yet there has been very little application to the packaging. The present article investigates issues involved in the recruitment and training of a sensory tactile expert panel for beverage packaging. The study addresses two important questions: what are the sensory tactile attributes that are usable for packages, and do the hand movements performed by each expert have an impact on the sensory response? The first part presents the research of sensory attributes and the training of two groups on different types of beverage packaging (glass, plastic, aluminum bottles). The performances of both groups have been controlled. In the second part, the impact of hand movements (kind of movement, variation, and strategy of haptic exploration) is demonstrated by a three-step experiment.