Search results

The choke flutter is a fluid-structure interaction that can lead to the failure of fan or compressor blade in turbojet engines. In ultra high bypass ratio (UHBR) fans, the choke flutter appears at part-speed regimes and at low or negative incidence when a strong shock-wave chokes the blade to blade channel. The purpose of this study is to locate the main excitation sources and improving the understanding of the different work exchange mechanisms. This work contributes to avoiding deficient and dangerous fan design.

In this paper, an UHBR fan is analyzed using a time-linearized Reynolds-averaged Navier–Stokes equation solver to investigate the choke flutter. The steady-state and the imposed vibration (inter blade phase angle, reduced frequency and mode shape) are selected to be in choke flutter situation. Superposition principle induced by the linearization allow to decompose the blade in numerous small subsections to track the contribution of each local vibration to the global damping. All simulations have been performed on a two-dimensional blade to blade extraction.

Result analysis points to a restricted number of excitation sources at the trailing edge which induce a large part of the work exchange in a limited region of the airfoil. Main phenomena suspected are the shock-wave motion and the shock-wave/boundary layer interaction.

An original excitation source tracking methodology allowed by the linearized calculation is addressed and applied to a UHBR fan test case.

Traditional embedded operation systems are resource consuming multitask, thus they are not adapted for smart wireless sensors. This paper presents a super‐small distributed real‐time microkernel (SDREAM) dedicated to wireless sensors. SDREAM is a tuple‐based message‐driven real‐time kernel. It adopts a meta language: Kernel Modeling Language to define and describe the system primitives in abstract manner. The IPC and processes synchronization are based on the LINDA concept: the tuple model implemented by two light primitives (SND: OUT & RCV: IN). In SDREAM, tasks are classified into two categories: periodic and priority. The periodic task has the highest priority level and is responsible for capturing sensor signals or actuating control signals; the priority task has various priority levels and is suitable for time‐constraints applications. A two‐level task scheduling policy scheme, named priority‐based pre‐emptive scheduling, is used for task scheduling. SDREAM is simple and efficient. It has a flexible hardware abstraction capability that enables it to be rapidly ported into different WSN platforms and other tiny embedded devices. Currently, it has been ported and evaluated in several hardware platforms. The performance results show SDREAM requires tiny resource and is suitable and efficient for hard real‐time multitask WSN applications.

The purpose of this paper is to present a frequency domain analysis of high frequency behaviour of an indoor Powerline communications (PLC) circuit in the presence of a plaster board/concrete wall structure. The main purpose of this analysis is to investigate the influence of the wall structure on the current distribution and the radiated electric field due to PLC signals in range from 3 MHz to 30 MHz.

The mathematical model is based on the full‐wave theory formulated by the Mixed Potential Integral Equation (MPIE) for the electric field due to energized thin‐wire conductors in stratified media. The solution for the current and the electric field distribution is obtained by using the Method of Moments.

Numerical results are obtained of the current distribution along the conductors of the PLC circuit and the radiated electric field in presence of a wall structure. Two cases are analyzed: when the circuitry is placed in the wall; and when the circuitry is placed outside the wall.

The paper presents the mathematical model that may be applied for analysis of indoor PLC circuits placed in presence of wall structures.

In the paper, a full‐wave model of the PLC circuitry in presence of a wall structure is developed, on the basis of MPIE and the Method of Moments.

Presents the kinematic calibration of an H4 parallel prototype robot using a vision‐based measuring device. Calibration is performed according to the inverse kinematic model method, using first the design model then a model developed for calibration purpose. To do so, the end‐effector pose (i.e. position and orientation) has to be measured with the utmost accuracy. Thus, first the practical accuracy of the low‐cost vision‐based measuring system is evaluated to have a precision in the order of magnitude of 10μ_it;m and 10^−3° for a 1,024×768 pixel CCD camera. Second, the prototype is calibrated using the easy‐to‐install vision system, yielding a final positioning accuracy of the end‐effector reduced from more than 1cm down to less than 0.5mm. Also provides a discussion on the use of such a method on commercial systems.

Two different configurations of steel-to-timber connections are tested in bending in normal conditions and under ISO-fire exposure. To observe the influence of clearances in the connection area on the fire resistance of the connections, two specimens were previously tested under cyclic loadings. These tests consist in the application of loading-unloading cycles by controlled displacements. The experimental results of connections tested in cold and under ISO-fire conditions are analyzed and commented. These results are then used to validate a finite element model. This model allows to simulate numerically the evolution of the temperatures inside the connections as well as their mechanical and thermo-mechanical behaviours. The thermal modelling is validated on the basis of the temperature-time evolutions measured during fire tests. The nonlinear modelling of the mechanical behaviour of timber is done using the Hill yield criterion in combination with the Tsaï-Wu failure criterion. The thermo-mechanical modelling allows obtaining fire resistances of the tested connections in good agreement with the experimental ones.

Health and education are inextricably linked. Health promotion sits somewhat uncomfortably within schools, often remaining a marginal aspect of teachers’ work. The purpose of this paper is to examine the compatibility of an HP-initiative with teacher professional identity.

A qualitative research design was adopted consisting of semi-structured interviews. In total, 49 teachers in two school districts in the Auvergne region in central France were interviewed in depth post having completed three years’ involvement in a health promoting schools initiative called “Learning to Live Better Together” (“Apprendre a Mieux Vivre Ensemble”).

Teachers in the study had a broad conceptualisation of their role in health promotion. In keeping with international trends, there was more success at classroom than at whole school level. While generally teachers can be reluctant to engage with health promotion, the teachers in this study identified having little difficulty in understanding their professional identity as health promoters and identified strong compatibility with the HP-initiative.

Teachers generally viewed professional development in health promotion in a positive light when its underlying values were commensurate with their own and when the context was seen as compatible with the school mission. The promotion of health in schools needs to be sensitive to professional identity and be tailored specifically to blend more successfully with current teacher identity and practice.

The promotion of health in schools needs to be sensitive to professional identity and be tailored specifically to blend more successfully with current teacher identity and practice.

The mechanization of the meat cutting companies has become essential. This paper aims to study the feasibility of cutting operations for beef and boning operations for pork ham. The study aims to enhance industrial robots application by using vision or force control.

The paper opted for an industrial robot‐based cell. The first part of this paper focuses on in‐depth study of operators' expertise, so as to translate their actions into automatable operative tasks and to identify the constraints of robotization. It details more particularly a cutting strategy using a bone as a guide which shows the complexity of the process. The analysis of the cutting and task constraint parameters involves the use of a kinematically redundant robotized cell with force control. Then the cell model is developed, and experimentation is performed.

The paper explains how to solve the problem of the high variability of the size for beef carcass. It gives several ideas to realize the boning of pork ham. It develops the strategies, the sensors and the cell architecture to make this type of operations.

Because of the choice of an existing industrial robot, the tool paths with force control are limited. Therefore, new force control instructions have to be developed to continue this work on more complicated operations.

This study was carried out within the framework of the SRDViand project in cooperation with meat industry partners.

The paper fulfils an identified need to study the beef quartering which is a high‐variability operation and ham deboning which is a high precision operation.

Considering the importance of supply chain integration (SCI) in literature and the increasing outsourcing of logistics, this paper aims to study the role of logistics service providers (LSPs) in supporting SCI and clients' performance.

This research is based on a two‐step approach: a literature review on supply chain integration (SCI) and performance regarding how LSPs are taken into account; and an analysis of web sites of LSPs concerning how they communicate their role and whether they themselves consider they have a role in improving the SCI and performance of their clients. Results are then discussed in view of some major works on third party logistics.

Some surprising conclusions are drawn. Among the analysed articles very few take LSPs into consideration. The web site analysis shows LSPs varying in their communication. Some do not consider SCI as part of their job, others balance between being pure “resource providers” and taking the riskier role of “supply chain designers”. The analysis of the roles LSPs can play in supply chains enriches the understanding of the SCI phenomenon.

In this paper SCI performance papers are analysed. A review of papers on LSPs could be another relevant starting point. The web site analysis concerns LSPs' communication. Further research could complement with the shippers' perspectives.

Results suggest different dimensions to structure LSPs' strategies vis‐à‐vis clients' SCI and performance.

The main contributions of this paper are questioning and analysing what role LSPs play in SCI and performance, and expanding the framework for SCI studies.

The purpose of this paper is to address optimal positioning of a group of mobile robots for a successful manipulation and transportation of payloads of any shape.

The chosen methodology to achieve optimal positioning of the robots around the payload to lift it and to transport it while maintaining a geometric multi-robot formation is presented. This appropriate configuration of the set of robots is obtained by combining constraints ensuring stable and safe lifting and transport of the payload. A suitable control law is then used to track a virtual structure in which each elementary robot has to keep its desired position with respect to the payload.

An optimal positioning of mobile robots around a payload to ensure stable co-manipulation and transportation task according to stability multi-criteria constraints. Simulation and experimental results validate the proposed control architecture and strategy for a successful transportation task based on virtual structure navigation approach.

This paper presents a new strategy for co-manipulation and co-transportation task based on a virtual structure navigation approach. An algorithm for optimal positioning of mobile robots around a payload of any mass and shape is proposed while ensuring stability during the whole process by respecting multi-criteria task stability constraints.

The purpose of this paper is to describe designing Pobot V2, a robot capable to climb poles with a cylindrical or conical shape.

This paper describes the design of the pole‐climbing robot Pobot V2, based on the innovative principle of rolling self‐locking that uses no energy to maintain itself at a given altitude.

The robot is also capable of avoiding tangential obstacles, crossing small collars and regulating passively its normal contact force on conical poles with a diameter that evolves from 300 to 100 mm. The work is validated by experiments. The robot can also perform axial rotation, can cross‐tangential obstacles and climb poles with a strong conical shape, due to passive normal force regulation with springs and a force amplifying linkage. The first experiments showed excellent stability during vertical climbing.

More work will be required to make the robot more rigid, more compact, and lighter. The robot is jointly patented by Thales and IFMA.

It is original because of its rolling self‐locking concept: rolling allows continuous ascension whereas self‐locking guarantees a null energy consumption while staying still on the pole.