Search results

The purpose of this paper is to present the original study of an industrial device. Industrial inductors are used to decrease the current variations, resulting from the use of modern power converters. To reduce these variations, the magnetic energy stored in these components is automatically used when the receptor is unconnected to the principal sources. Such storage is generally obtained by using a magnetic circuit containing air‐gaps. The rigidity of this circuit, associated with the magnetic stresses which appear in these areas, causes the structure to produce mechanical vibration and to emit audible sounds.

Experiments, simulations and test devices are used to determine the main physical phenomenon that generates the undesirable audible noise. The resulting knowledge is used to design a quieter device.

The mechanical vibrations and emitted noises are attached to magnetic effects. Even if it is not possible to suppress all these effects, the level of sound emitted can be decreased through a suitable design of the magnetic core.

Industrial inductors are usually built and designed using methods coming from the transformer studies. A new concept for the design of the magnetic core is presented. Experimental approaches and numerical simulations are performed in order to highlight the physical behaviours of the coils and their magnetic coupling to the magnetic core. It appears that breaking the magnetic core into free parts is an original solution that decreases the emitted noise.

The purpose of this paper is to introduce a simplified method to calculate an estimation of local forces acting on a body submitted to electric or magnetic fields. With experimentations, the method is thereafter evaluated.

When an external strength exists on a body, its deformation is an effect always observed. With materials with low elasticity modulus, such a deformation becomes visible and its measurement can be used to validate numerical simulations. Using similarities between electric and magnetic behaviour laws, magnetic problems can be modelled with an electric field approach and studied with an experiment that also uses an electric field.

Geometrical singularities and their effects on calculations are not always well taken into account by a finite element resolution. An adaptive mesh refinement is often required. If such mesh refinement is refused, another solution can be explored. The goal is to know the external stress distribution induced by the field. The methods only focus on this stress distribution and assume that the magnetic or electric field distribution is imprecise when it is calculated near geometrical singularities. The stress distributions suggested are verified with experiments.

Using new materials with particular physical properties provides a new concept of experimental validation.

The archives of François Perroux deposited at IMEC bear witness to the fact that he has devoted, beyond his scientific production, great energy to the most material aspects of research: setting up and maintaining networks to publicize his work and that of other economists, either directly or through the institutes and the journals he headed; organize seminars and symposiums; take care of relations with colleagues and the press; create collections and journals; and so on.

In this chapter, we concentrate our attention on the archives relating to the management of the institutes, those attesting to the lines and themes of the producer’s research, and those concerning his important correspondence.

Thanks to the archives deposited at IMEC, it is possible to follow the development of the theoretical work of François Perroux by contextualizing it. They also show the itinerary of a Christian intellectual, whose attachment to social Catholicism constitutes a guiding thread and is reflected in all his activities. Finally, the archives illuminate his substantial role in the institutionalization of research in economics in the France of the twentieth century.

The purpose of this paper is to refine and measure esthetic development.

Three phrases of data collection were conducted utilizing four separate student samples (n = 120, 154, 241, and 343). In Phase I, an initial esthetic development stage model was tested with a constructed response test format using generalizability measurement theory. In Phase II, this conceptual model in esthetic development was refined with a modified constructed response format. In Phase III, a selective response test format was designed with five esthetic development stage scores, which were correlated with several artistic discipline-based and interdisciplinary courses.

Higher esthetic development stages correlate with verbal ability and grades in interdisciplinary general education arts courses. Lower esthetic development stages were associated with lower verbal ability and grades in traditionally taught discipline-based arts courses.

What this study did not do is examine whether attendance at arts events and activities support or lead to higher esthetic development.

People at Stages Four and Five of this esthetic development model are able to compare artistic experience – whether visual or performing art – within a historical and cultural context or perspective. Individuals at these highest stages are able to communicate about the social significance and societal themes of the artistic experience to wider audiences.

No accepted model or assessment method about the arts in higher education is available. Although the arts are commonly accepted as important in higher education, there is a paucity of research about esthetic development in the curriculum. This paper attempts to address this gap, in part, and to advance further study about quality of arts’ programs and activities in higher education.

The determination of the vibration induced by an aircraft impact on an industrial structure requires dynamic studies. The determination of the response by using classical finite element method associated with explicit numerical schemes requires significant calculation time, especially during the transient stage. This kind of calculation requires several load cases to be analyzed in order to consider a wide range of scenarios. Moreover, a large frequency range has to be appropriately considered and therefore the mesh has to be very fine, resulting in a refined time discretization. The purpose of this paper is to develop new ways for calculating the shaking of reinforced concrete structures following a commercial aircraft impact (see Figure 1). The cutoff frequency for this type of loading is typically within the 50-100 Hz range, which would be referred to as the medium-frequency range.

Taking into account this type of problem and assuming that the structure is appropriately sized to withstand an aircraft impact, the vibrations induced by the shock bring about shaking of the structure. Then these vibrations can travel along the containment building, as directly linked with the impact zone, but also in the inner part of the structure due to the connection with the containment building by the raft. So the excited frequency range, due to the impact of a commercial aircraft, contains two frequency ranges: low frequencies (less than ten wavelengths in the structure) and medium frequencies (between ten and 100 wavelengths). The strategy, which is presented in this paper, is inscribed in the context of the verification of inner equipment under this kind of shaking. The non-linear impact zone is assumed to have been delimited with classical finite element simulations. In this paper the authors only focus on the response of the linear part of the structure. This phenomenon induces a non-linear localized area around the impact zone.

So the medium frequencies can therefore induce significant displacements and stresses at the level of equipment and thus cause damage if the structure is not dimensioning to this frequency range.

In this context the use of finite elements method for the resolution of the shaking implies a spatial discretization in correlation with the number of wavelengths to represent, and thus a long computation time especially for medium frequencies. That is why in the case of a coarse mesh the medium-frequency range is ignored. For example, a concrete structure with a characteristic dimension of about 30 and 1 m of thickness, may not represent frequencies higher than 16 Hz with a mesh size of 1 m (assuming ten elements per wavelength).

The paper includes implications for proper dimensioning civil engineering structures subjected to a load case containing a large frequency range.

This paper shows the gain of the strategy using appropriate method to medium frequencies compared to conventional method such as finite elements.