Remy Springs - Academia.edu (original) (raw)

Papers by Remy Springs

Research paper thumbnail of Optimization of detectors positioning with respect to flying dynamics for future formation flight missions

In a X-ray telescope in formation flight configuration, the optics and the focal-plane detectors ... more In a X-ray telescope in formation flight configuration, the optics and the focal-plane detectors reside in two different spacecraft. The dynamics of the detector spacecraft (DSC) with respect to the mirror spacecraft (MSC, carrying the mirrors of the telescope) changes continuously the arrival positions of the photons on the detectors. In this paper we analyze this issue for the case of the SIMBOL-X hard X-ray mission, extensively studied by CNES and ASI until 2009 spring. Due to the existing gaps between pixels and between detector modules, the dynamics of the system may produce a relevant photometric effect. The aim of this work is to present the optimization study of the control-law algorithm with respect to the detector's geometry. As the photometric effect may vary depending upon position of the source image on the detector, the analysis-carried out using the simuLOS (INAF, CNES, CEA) simulation tool-is extended over the entire SIMBOL-X field of view.

Research paper thumbnail of Chikungunya Outbreaks — The Globalization of Vectorborne Diseases

New England Journal of Medicine, 2007

Research paper thumbnail of Three-year-old child neck finite element modelization

European Journal of Orthopaedic Surgery and Traumatology, 2006

Despite the recent progresses in occupant safety, protection of children is not still optimal. To... more Despite the recent progresses in occupant safety, protection of children is not still optimal. To offer a better understanding of child injury mechanisms, the present study proposes a human-like finite element model of a 3-year-old child neck. The subject underwent scanning. The images were first segmented semi-automatically in order to extract the soft tissues and the bones. In the second step, we separated the different bones slice by slice on the geometry previously reconstructed. The anatomic structures were identified and each vertebra was reconstructed independently with special attention to the articular process. In the third step, we generated an original meshing on the previous geometry to obtain a finite element model of the child’s neck. The modelled anatomical structures are the head, the seven cervical vertebrae (C1–C7), the first thoracic vertebra (T1), the intervertebral discs and the principal ligaments which were modelled using non-linear shock-absorbing spring elements. The stiffness values used were taken from the literature, and scaled down using scale factors from Irwin. This model incorporates 7,340 shell elements to model the 8 vertebrae, the head and 1,068 solid 8-node elements to model the intervertebral discs. Contact between the articular surfaces is represented by interfaces permitting frictionless movement. Since this study does not aim to reproduce bone fractures, we have modelled the cervical vertebrae as rigid bodies. Given that validation data was not available, the model validation was conduced against crash test dummy component sled tests. The accelerometric responses of the head model were similar with those recorded experimentally with a Q3 dummy neck in backward, frontal and lateral impact direction. Malgré l’évolution récente des systèmes de protection dans les automobiles, les traumatismes du rachis cervical de l’enfant restent encore un problème d’actualité. Le sujet de cette étude est donc la création et la validation d’un modèle éléments finis tridimensionnel détaillé du rachis cervical d’un enfant de trois ans, destiné à améliorer la compréhension des mécanismes lésionnels en situation de choc. Pour ce faire, nous sommes partis de coupes scanographiques; les images ont d’abord été seuillées de manière semi-automatique pour extraire les parties osseuses. Les vertèbres ont été identifiées coupes par coupes sur la base de la géométrie ainsi reconstruite. Dans un second temps, à partir de la géométrie obtenue, nous avons généré un maillage original comprenant le crâne, les sept vertèbres cervicales, la première vertèbre thoracique, les disques intervertébraux et les principaux ligaments. Les huit vertèbres ainsi que le crâne ont été modélisés par des éléments coques, les disques intervertébraux par des éléments volumiques et les ligaments par des éléments ressorts. Les éléments osseux se sont vus déclarés en tant que corps rigides puisque l’étude ne prend pas en compte la rupture osseuse. Les ligaments ont été modélisés par des ressorts viscoélastiques non-linéaires dont les valeurs de raideur sont issues de la littérature et ont été ajustés selon les coefficients d’échelle de Irwin. Le contact entre les surfaces articulaires est géré par des interfaces sans frottement. Du fait de l’absence de données expérimentales sur le comportement de l’enfant en situation d’impact, nous avons mené des essais chariots sur le cou d’un mannequin de crash Q3. Les réponses numériques de la tête en terme d’accélération étaient similaires à celles mesurées expérimentalement en choc avant, arrière et latéral.

Research paper thumbnail of Optimization of detectors positioning with respect to flying dynamics for future formation flight missions

In a X-ray telescope in formation flight configuration, the optics and the focal-plane detectors ... more In a X-ray telescope in formation flight configuration, the optics and the focal-plane detectors reside in two different spacecraft. The dynamics of the detector spacecraft (DSC) with respect to the mirror spacecraft (MSC, carrying the mirrors of the telescope) changes continuously the arrival positions of the photons on the detectors. In this paper we analyze this issue for the case of the SIMBOL-X hard X-ray mission, extensively studied by CNES and ASI until 2009 spring. Due to the existing gaps between pixels and between detector modules, the dynamics of the system may produce a relevant photometric effect. The aim of this work is to present the optimization study of the control-law algorithm with respect to the detector's geometry. As the photometric effect may vary depending upon position of the source image on the detector, the analysis-carried out using the simuLOS (INAF, CNES, CEA) simulation tool-is extended over the entire SIMBOL-X field of view.

Research paper thumbnail of Chikungunya Outbreaks — The Globalization of Vectorborne Diseases

New England Journal of Medicine, 2007

Research paper thumbnail of Three-year-old child neck finite element modelization

European Journal of Orthopaedic Surgery and Traumatology, 2006

Despite the recent progresses in occupant safety, protection of children is not still optimal. To... more Despite the recent progresses in occupant safety, protection of children is not still optimal. To offer a better understanding of child injury mechanisms, the present study proposes a human-like finite element model of a 3-year-old child neck. The subject underwent scanning. The images were first segmented semi-automatically in order to extract the soft tissues and the bones. In the second step, we separated the different bones slice by slice on the geometry previously reconstructed. The anatomic structures were identified and each vertebra was reconstructed independently with special attention to the articular process. In the third step, we generated an original meshing on the previous geometry to obtain a finite element model of the child’s neck. The modelled anatomical structures are the head, the seven cervical vertebrae (C1–C7), the first thoracic vertebra (T1), the intervertebral discs and the principal ligaments which were modelled using non-linear shock-absorbing spring elements. The stiffness values used were taken from the literature, and scaled down using scale factors from Irwin. This model incorporates 7,340 shell elements to model the 8 vertebrae, the head and 1,068 solid 8-node elements to model the intervertebral discs. Contact between the articular surfaces is represented by interfaces permitting frictionless movement. Since this study does not aim to reproduce bone fractures, we have modelled the cervical vertebrae as rigid bodies. Given that validation data was not available, the model validation was conduced against crash test dummy component sled tests. The accelerometric responses of the head model were similar with those recorded experimentally with a Q3 dummy neck in backward, frontal and lateral impact direction. Malgré l’évolution récente des systèmes de protection dans les automobiles, les traumatismes du rachis cervical de l’enfant restent encore un problème d’actualité. Le sujet de cette étude est donc la création et la validation d’un modèle éléments finis tridimensionnel détaillé du rachis cervical d’un enfant de trois ans, destiné à améliorer la compréhension des mécanismes lésionnels en situation de choc. Pour ce faire, nous sommes partis de coupes scanographiques; les images ont d’abord été seuillées de manière semi-automatique pour extraire les parties osseuses. Les vertèbres ont été identifiées coupes par coupes sur la base de la géométrie ainsi reconstruite. Dans un second temps, à partir de la géométrie obtenue, nous avons généré un maillage original comprenant le crâne, les sept vertèbres cervicales, la première vertèbre thoracique, les disques intervertébraux et les principaux ligaments. Les huit vertèbres ainsi que le crâne ont été modélisés par des éléments coques, les disques intervertébraux par des éléments volumiques et les ligaments par des éléments ressorts. Les éléments osseux se sont vus déclarés en tant que corps rigides puisque l’étude ne prend pas en compte la rupture osseuse. Les ligaments ont été modélisés par des ressorts viscoélastiques non-linéaires dont les valeurs de raideur sont issues de la littérature et ont été ajustés selon les coefficients d’échelle de Irwin. Le contact entre les surfaces articulaires est géré par des interfaces sans frottement. Du fait de l’absence de données expérimentales sur le comportement de l’enfant en situation d’impact, nous avons mené des essais chariots sur le cou d’un mannequin de crash Q3. Les réponses numériques de la tête en terme d’accélération étaient similaires à celles mesurées expérimentalement en choc avant, arrière et latéral.