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101. Monte Carlo Assessment of Spatial and Energy Effects in the VENUS-F Subcritical Configurations and Application for Reactivity Determination

Author

Bécares, V., Villamarín, D., González-Romero, E. M., Kochetkov, A., Baeten, P., Uyttenhove, W., Vittiglio, G., Wagemans, J., Billebaud, A., Chabod, S., Lecouey, J. L., Lecolley, F. R., Lehaut, G., Nathalie Marie, Doliguez, X., Mellier, F., Centre d'Etude de l'Energie Nucléaire (SCK-CEN), Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de physique corpusculaire de Caen (LPCC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Institut de Physique Nucléaire d'Orsay (IPNO), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), and Guesnon, Sandrine

Subjects
[PHYS.NEXP] Physics [physics]/Nuclear Experiment [nucl-ex], [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
Abstract

International audience; Experiments with a subcritical core and an external pulsed neutron source (PNS) have been performed at the VENUS-F reactor of theSCK-CEN during the year 2012 within the frame of the FREYA project of the 7th European Framework Programme. Different reactivity levels,obtained by varying the position of the control rods and the safety rods, have been investigated, with values of kef f ranging between 0.9and 0.96. The area-ratio and the prompt decay constant techniques are well-known techniques to determine the reactivity of the systemfrom the results of PNS experiments. However, both techniques are based on the point kinetics model and hence they are affected by thespatial and energy effects present in real systems, which will cause them to produce biased values of the reactivity. In this work, we applya methodology based on Monte Carlo simulations to assess the spatial and energy effects present in the VENUS-F core and to determinerelationships between the reactivity and the measured parameters (area-ratio and prompt decay constant) that take into account these effects and allow the application of the reactivity determination techniques to obtain accurate reactivity values beyond the limits of the point kinetics model. The results of the validation of this methodology against the experimental results obtained in the VENUS-F reactor will also be discussed.

Published
2014

102. Interpretation of experimental measurements on the SC-1 configuration of the VENUS-F core

Author

Dulla, Sandra, Nervo, Marta, Ravetto, Piero, Mila, G., Argirò, S., Beolè, S., Masera, M., Bianchini, G., Carta, M., Fabrizio, V., Peluso, V., Gabrielli, F., Rineiski, A., Kochetkov, A., Baeten, P., Uyttenhove, W., Vittiglio, G., and Wagemans, J.

Subjects
source-driven subcritical systems, FREYA Project, pulsed experiments, subcriticality level monitoring
Published
2014

103. Perceptual completions

Author

Wagemans, J., Lier, R.J. van, Gerbino, W., Wagemans, J., Lier, R.J. van, and Gerbino, W.

Abstract

Item does not contain fulltext

Published
2015

107. Mutual interplay between perceptual organization and attention: a neuropsychological perspective

Author

Gillebert, CR, Humphreys, GW, and Wagemans, J

Abstract

An efficient representation of the environment requires both the selection of a fraction of the information that reaches our senses and the organization of this information into coherent and meaningful elements. Here we discuss the dynamic interplay between selective attention and perceptual organization, important processes that allow us to perceive a seamless, integrated world. Based on evidence from behavioral and neuroimaging studies with normal observers and neuropsychological patients, we examine whether: (i) perceptual grouping constrains visual attention, determining which objects will be selected and be candidates for explicit report; (ii) visual attention modulates perceptual grouping, determining how elements are grouped to form meaningful wholes. The data suggest that, whilst not being necessary for at least some forms of perceptual grouping, visual attention can nevertheless modulate grouping. We conclude that selection is dynamically set by bottom-up stimulus factors, top-down knowledge and the allocation of attention to space and within grouped regions of objects.

Published
2013

108. Current progress and future plans of the FREYA Project

Author

Kochetkov, A., Baeten, P., Billebaud, A., Chabod, S., Doligez, X., Lecolley, F. R., Lecouey, J. L., Lehaut, G., Nathalie Marie, Mellier, F., Thyébault, H. E., Uyttenhove, W., Vittiglio, G., Wagemans, J., Ban, G., Dessagne, P., Kerveno, M., Mercatali, L., Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique Nucléaire d'Orsay (IPNO), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Laboratoire de physique corpusculaire de Caen (LPCC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Institut Pluridisciplinaire Hubert Curien (IPHC), Université de Strasbourg (UNISTRA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and Guesnon, Sandrine

Subjects
[PHYS.NEXP] Physics [physics]/Nuclear Experiment [nucl-ex], [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
Abstract

International audience; Reactor physics experiments are required for the design of a Fast Spectrum TransmutationExperimental Facility MYRRHA/FASTEF working in subcritical mode and in critical mode.Reactor physics experiments aim to validate a methodology for on-line subcriticalitymonitoring. For this purpose, building on the former activities accomplished in the previousFP6 project GUINEVERE, investigations on the subcritical VENUS-F (lead/uranium) corescoupled with the GENEPI-3C accelerator will be extended. This activity has been planned inwithin the framework of the on-going FREYA (Fast Reactor Experiments for hYbridApplications) FP7 project. This paper presents the current progress of the project and thefuture plans.

Published
2013

109. Reactivity monitoring using the area method for the subcritical VENUS-F core within the framework of the FREYA Project

Author

Nathalie Marie, Lehaut, G., Lecouey, J. L., Billebaud, A., Chabod, S., Doligez, X., Lecolley, F. R., Kochetkov, A., Uyttenhove, W., Vittiglio, G., Wagemans, J., Mellier, F., Ban, G., Thyébault, H. E., Villamarin, D., Laboratoire de physique corpusculaire de Caen (LPCC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique Nucléaire d'Orsay (IPNO), and Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)

Subjects
Physics - Instrumentation and Detectors, FOS: Physical sciences, Instrumentation and Detectors (physics.ins-det), Nuclear Experiment (nucl-ex), [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Experiment
Abstract

Accelerator-Driven Systems (ADS) could be employed to incinerate minor actinides and so partly contribute to answer the problem of nuclear waste management. An ADS consists of the coupling of a subcritical fast reactor to a particle accelerator via a heavy material spallation target. The on-line reactivity monitoring of such an ADS is a serious issue regarding its safety. In order to study the methodology of this monitoring, zero-power experimentswere undertaken at the GUINEVERE facility within the framework of the FP6-IP-EUROTRANS programme. Such experiments have been under completion within the FREYA FP7 project. The GUINEVERE facility is hosted at the SCK-CEN site in Mol (Belgium). It couples the VENUS-F subcritical fast core with the GENEPI-3C accelerator. The latter delivers a beam of deuterons, which are converted into 14-MeV neutrons via fusion reactions on a tritiated target. This paper presents one of the investigated methods for ADS on-line reactivity monitoring which has to be validated in the program of the FREYA project. It describes the results obtained when Pulsed Neutron Source experiments are analysed using the so called Area Method, in order to estimate the reactivity of a few sub-critical configurations of the VENUS-F reactor, around keff= 0.96. First the GUINEVERE facility is described. Then, following general considerations on the Area method, the results of its application to the neutron population time decrease spectra measured after a pulse by several fission chambers spread out over the whole reactor are discussed. Finally the reactivity values extracted are compared to the static reactivity values obtained using the Modified Source Multiplication (MSM) method., Comment: International Workshop on Technology and Components of Accelerator Driven Systems (TCADS) OECD Nuclear Energy Agency, Nantes : France (2013)

Published
2013

110. Analysis of prompt decay experiments for ADS reactivity monitoring at VENUS-F GUINEVERE facility

Author

Chabod, S., Doligez, X., Lehaut, G., Billebaud, A., Lecouey, J. L., Lecolley, F. R., Nathalie Marie, Kochetkov, A., Uyttenhove, W., Vittiglio, G., Wagemans, J., Mellier, F., Ban, G., Thyébault, H. E., Villamarin, D., Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique Nucléaire d'Orsay (IPNO), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Laboratoire de physique corpusculaire de Caen (LPCC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), and Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)

Subjects
[PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2013

111. An alternative source Jerk method implementation for the subcriticality estimation of the Venus-F subcritical core in the FREYA project

Author

Kochetkov, A., Ban, G., Baeten, P., Billebaud, A., Chabod, S., Doligez, X., Lecolley, F. R., Lecouey, J. L., Lehaut, G., Nathalie Marie, Mellier, F., Thyébault, H. E., Uyttenhove, W., Vittiglio, G., Wagemans, J., Laboratoire de physique corpusculaire de Caen (LPCC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), and Guesnon, Sandrine

Subjects
[PHYS.NEXP] Physics [physics]/Nuclear Experiment [nucl-ex], [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
Published
2013

112. On Visual Gestalt formation [Editorial]

Author

Helm, P.A. van der, Lier, R.J. van, and Wagemans, J.

Subjects
Action, intention, and motor control
Abstract

Item does not contain fulltext This special issue appears on the occasion of Emanuel Leeuwenberg’s retirement. During 40yea rs of research on visual perception, Leeuwenberg studied a wide range of topics, such as judged complexity, neon effects, subjective contours, visual pattern completion, ambiguity, assimilation and contrast, temporal order, beauty, object handedness, veridicality, and visual regularity. To him, the empirical study of these topics is not a goal in itself but rather a means to focus on underlying principles of perceptual organization. Most prominently, he advocated the simplicity principle which states that, from among all possible interpretations of a pattern, the visual system selects the interpretation with the simplest description.

Published
2003

113. The GUINEVERE Experiment: first PNS measurements in a lead moderated sub-critical fast core

Author

Thyébault, H. E., Baeten, P., Billebaud, A., Chabod, S., Kochetkov, A., Lecolley, F. R., Lecouey, J. L., Lehaut, G., Nathalie Marie, Mellier, F., Uyttenhove, W., Vittiglio, G., Wagemans, J., Ban, G., Dessagne, P., Kerveno, M., Steckmeyer, J. C., Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de physique corpusculaire de Caen (LPCC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Institut Pluridisciplinaire Hubert Curien (IPHC), Université de Strasbourg (UNISTRA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), GUINEVERE, and Vernay, Emmanuelle

Subjects
[PHYS.NEXP] Physics [physics]/Nuclear Experiment [nucl-ex], [PHYS.PHYS.PHYS-ACC-PH]Physics [physics]/Physics [physics]/Accelerator Physics [physics.acc-ph], [PHYS.PHYS.PHYS-ACC-PH] Physics [physics]/Physics [physics]/Accelerator Physics [physics.acc-ph], [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
Abstract

Item ID: 700368 / ISBN: 978-0-89448-091-1; International audience

Published
2012

114. Detector positioning for the initial subcriticality level determination in Accelerator-Driven Systems

Author

Uyttenhove, W., Den Eynde, G., Baeten, P., Kochetkov, A., Vittiglio, G., Wagemans, J., Lathouwers, D., Kloosterman, J. L., Hagen, T. J. H. H., Wols, F., Billebaud, A., Chabod, S., Thyebault, H. E., Lecouey, J. L., Ban, G., Lecolley, F. R., Nathalie Marie, Steckmeyer, J. C., Dessagne, P., Kerveno, M., Mellier, F., Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de physique corpusculaire de Caen (LPCC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Département Recherches Subatomiques (DRS-IPHC), Institut Pluridisciplinaire Hubert Curien (IPHC), Université de Strasbourg (UNISTRA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and Vernay, Emmanuelle

Subjects
Hardware_MEMORYSTRUCTURES, [PHYS.NEXP] Physics [physics]/Nuclear Experiment [nucl-ex], Hardware_CONTROLSTRUCTURESANDMICROPROGRAMMING, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
Abstract

CD Rom, paper 299

Published
2012

119. Effective delayed neutron fraction measurement in the critical VENUS-F reactor using noise techniques

Author

Doligez, X., primary, Billebaud, A., additional, Chabod, S., additional, Chevret, T., additional, Fourmentel, D., additional, Krasa, A., additional, Kochetkov, A., additional, Lecolley, F. R., additional, Lecouey, J. L., additional, Lehaut, G., additional, Marie, N., additional, Mellier, F., additional, Vittiglio, G., additional, and Wagemans, J., additional

Published
2015
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120. Thermal fission cross section measurements of 243Cm and 245Cm

Author

Popescu, L, Heyse, J, Wagemans, J, Wagemans, Cyrillus, Wagemans, Cyrillus, Wagemans, Jan, and D'hondt, Pierre

Subjects
Physics and Astronomy
Abstract

A new measurement program was set up at SCK-CEN to determine the thermal neutroninduced fission cross section of a number of Cm isotopes. The experiments are performed at a thermal neutron beam from the graphite moderated reactor BR1 at SCK-CEN. This paper presents preliminary results of our ^243Cm(n,f) and ^245Cm(n,f) cross-section measurements.

Published
2010

122. Memory effects in bi-stable depth-order perception: Influence of active and passive intermittent presentation of images

Author

Hermans, L., Stuer, D., Ee, R. van, Wagemans, J., Kogo, N., Hermans, L., Stuer, D., Ee, R. van, Wagemans, J., and Kogo, N.

Abstract

Contains fulltext : 135141.pdf (Publisher’s version ) (Closed access), The assignment of the “owner side” of a border, is an important aspect in the computation of depth- order and figure-ground organization. There is evidence for the existence of border-ownership (BOWN) sensitive neurons in the lower visual cortex. A neural circuit of a feedback system has been suggested in which BOWN computation is influenced by depth-order, while depth-order is constructed from BOWN signals. We recently developed a neuro-computational model, which implemented this idea [Kogo et al., 2011, Vision Research, 51(18), 2085-2098]. This Differentiation Integration for Surface Completion (DISC) model reproduces bi-stable depth-order perception by adding noise and adaptation. The DISC model predicts that passive intermittent presentation of an image stabilizes the perception. This perceptual stabilization is also called prolongation effect and demonstrates the influence of recent history of visual experiences in bi-stable depth-order perception. Furthermore, it has been reported that an active intermittent presentation by opening and closing eyes caused an even stronger stabilization [Leopold et al., 2002, Nature Neuroscience, 5(6), 605-609]. In this study, we investigated the prolongation effect by a passive intermittent presentation using Kanizsa’s anomalous transparency (KAT) image, Rubin’s face or vase (FV) image and the Necker cube (NC). The prolongation effect was observed in KAT and NC, but not in FV. In addition, we investigated the prolongation effect when subjects saw the images intermittently by opening and closing their eyes. The prolongation is further enhanced, which suggests that a higher level expectation influences the perceptual organization when ambiguous images are presented.

Published
2014

123. What’s your diagnosis?

Author

Clement, Paul and Wagemans, J

Abstract

ispartof: Belgian Journal of Medical Oncology vol:2 issue:5 pages:293-293 status: published

Published
2008

124. Ballistocardiogram artifacts in simultaneous EEG-fMRI acquisitions

Author

Vanderperren, K., Ramautar, J.R., Novitskiy, N., de Vos, M., Mennes, M., Vanrumste, B., Stiers, P., van den Bergh, B., Wagemans, J., Lagae, L., Sunaert, S., Van Huffel, S., Developmental Psychology, Neuropsychology & Psychopharmacology, and RS: FPN NPPP I

Subjects
SISTA, biomedical signal processing, ComputingMilieux_LEGALASPECTSOFCOMPUTING, DSP
Abstract

Vanderperren, K., Ramautar, J., Novitskiy, N., De Vos, M., Mennes, M., Vanrumste, B., Stiers, P., Van den Bergh, B., Wagemans, J., Lagae, L., Sunaert, S., Van Huffel, S. (2007). Ballistocardiogram artifacts in simultaneous EEG-fMRI acquisitions. International Journal of Bioelectromagnetism, 9 (3), 146-150.

Published
2007

125. Retrospective Dosimetry of Fast Neutrons Focused on the Reactions 93Nb(n,n')93Nbm and 54Fe(n,p)54Mn

Author

Voorbraak, W. P., Kekki, Tommi, Serén, Tom, Van Bockxstaele, M., Wagemans, J., Woittiez, J. R. W., Vehar, David, Gilliam, David, and Adams, James

Subjects
neutron fluence, neutron damage, manganese, retrospective dosimetry, niobium, liquid scintillation counting, column anion exchange, neutron activation analysis
Abstract

An overview is given of practices for retrospective dosimetry based on extraction and counting of niobium and manganese present in typical pressure vessel materials. The main problem of counting structural materials is the overwhelming presence of the nuclide 60Co in the gamma-ray spectra of irradiated materials. Chemical separation of niobium and manganese is needed to determine the induced 93Nbm and 54Mn activities. Procedures have been developed for retrospective dosimetry applicable at normally equipped radiochemical laboratories. Chemical separation procedures have been applied followed by determination of the amount of niobium in dissolution after separation. Special attention has been given to the accurate counting of the very weak X rays of 93Nbm. Different techniques have been applied. Advantages, disadvantages, and the accuracy that can be achieved are discussed. Special attention has been given to the maximum accuracy that can be reached and the minimum amount of niobium that has to be collected to reach this accuracy.

Published
2007
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136. Miniature Fission Chambers Calibration in Pulse Mode: Interlaboratory Comparison at the ${\rm SCK}\bullet{\rm CEN}$ BR1 and CEA CALIBAN Reactors

Author

Lamirand, V., primary, Geslot, B., additional, Wagemans, J., additional, Borms, L., additional, Malambu, E., additional, Casoli, P., additional, Jacquet, X., additional, Rousseau, G., additional, Gregoire, G., additional, Sauvecane, P., additional, Garnier, D., additional, Breaud, S., additional, Mellier, F., additional, Di Salvo, J., additional, Destouches, C., additional, and Blaise, P., additional

Published
2014
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138. Reduced accuracy and sensitivity in the perception of emotional facial expressions in individuals with high autism spectrum traits

Author

Poljac, E., Wagemans, J., Poljac, E., and Wagemans, J.

Abstract

Item does not contain fulltext, Autism spectrum disorder (ASD) is among other things characterized by specific impairments in emotion processing. It is not clear, however, to what extent the typical decline in affective functioning is related to the specific autistic traits. We employed The Autism Spectrum-Quotient (AQ) to quantify autistic traits in a group of 500 healthy individuals and investigate whether we could detect similar difficulties in the perception of emotional expressions in a broader autistic phenotype. The group with high AQ score was less accurate and needed higher emotional content to recognize emotions of anger, disgust, and sadness. Our findings demonstrate a selective impairment in identification of emotional facial expressions in healthy individuals that is primarily related to the extent of autistic traits.

Published
2013

139. Preparation and characterization of a $^{39}Ar$ sample and study of the $^{39}Ar(n_{th},\alpha)^{36}S$ reaction

Author

Goeminne, G, Denecke, B, Geltenbort, P, Johansson, L, Köster, U, Pommé, S, Wagemans, C, and Wagemans, J

Subjects
Nuclear Physics - Experiment
Abstract

The $^{39}$Ar(n$_{\rm th}$,$\alpha$)$^{36}$S reaction has been studied for the first time. A sample containing $2.85 \times 10^{14}$ $^{39}$Ar atoms, was produced at the ISOLDE facility at CERN. The number of $^{39}$Ar atoms in the layer was determined by measuring the $^{39}$Ar $\beta$-activity using a primary standardization method. Subsequently, the sample was irradiated with thermal neutrons at the High Flux Reactor of the ILL. An upper limit of 0.29~b was obtained for the $^{39}$Ar(n$_{\rm th}$,$\alpha$)$^{36}$S reaction cross-section.

Published
2002

140. Energy distributions and yields of 3H, 4He and 6He-particles emitted in the 245Cm(n_th,f) reaction

Author

Serot, O, Wagemans, C, Wagemans, J, Goeminne, G, Köster, U, Geltenbort, P, and Nesvizhevsky, V V

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Nuclear Physics
Abstract

The energy distributions and yields of light charged particles emitted during thermal neutron induced fission of 245Cm have been measured at the high flux reactor of the Institute Laue Langevin in Grenoble (France). The detection of the ternary particles was done using a Delta-E/E telescope, permitting a good separation of the ternary particles. In this way, the characteristics of the energy distribution (average energy and full width at half maximum) for 4He, 3H and 6He particles as well as their emission probabilities could be determined. For the emission probabilities per fission, the following values were obtained: LRA/B=(2.15+-0.05)E-3, 3H/B=(1.85+-0.10)E-4 and 6He/B=(4.95+-1.25)E-5.

Published
2001

142. Perceptual wholes can reduce the conscious accessibility of their parts

Author

Poljac, E., de-Wit, L., Wagemans, J., Poljac, E., de-Wit, L., and Wagemans, J.

Abstract

Item does not contain fulltext, Humans can rapidly extract object and category information from an image despite surprising limitations in detecting changes to the individual parts of that image. In this article we provide evidence that the construction of a perceptual whole, or Gestalt, reduces awareness of changes to the parts of this object. This result suggests that the rapid extraction of a perceptual Gestalt, and the inaccessibility of the parts that make up that Gestalt, may in fact reflect two sides of the same coin whereby human vision provides only the most useful level of abstraction to conscious awareness.

Published
2012

143. Interaction of depth probes and style of depiction

Author

Doorn, A.J. (Andrea) van, Koenderink, J.J., Leyssen, M.H.R. (Mieke), Wagemans, J. (Johan), Doorn, A.J. (Andrea) van, Koenderink, J.J., Leyssen, M.H.R. (Mieke), and Wagemans, J. (Johan)

Abstract

We study the effect of stylistic differences on the nature of pictorial spaces as they appear to an observer when looking into a picture. Four pictures chosen from diverse styles of depiction were studied by 2 different methods. Each method addresses pictorial depth but draws on a different bouquet of depth cues. We find that the depth structures are very similar for 8 observers, apart from an idiosyncratic depth scaling (up to a factor of 3). The differences between observers generalize over (very different) pictures and (very different) methods. They are apparently characteristic of the person. The differences between depths as sampled by the 2 methods depend upon the style of the picture. This is the case for all observers except one.

Published
2012

144. Awareness of the light field: The case of deformation

Author

Van Doorn, A.J. (author), Koenderink, J.J. (author), Todd, J.T. (author), Wagemans, J. (author), Van Doorn, A.J. (author), Koenderink, J.J. (author), Todd, J.T. (author), and Wagemans, J. (author)

Abstract

Human observers group local shading patterns into global super-patterns that appear to be illuminated in some unitary fashion. Many years ago, this was noticed for the case of uniform, unidirectional illumination. Recently, we found that it also applies to convergent and divergent illumination flows, but that human observers are blind to rotational light flow patterns (in the sense of being unable to group the local shading patterns). We now report that human observers are also blind to deformation patterns. This is perhaps interesting because convergent, divergent, rotational, and deformation patterns all occur in natural light fields. This is an idiosyncrasy of the human visual system, on par with the fact that visual awareness fails to present the observer with saddle shapes., Industrial Design, Industrial Design Engineering

Published
2012
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145. Interaction of depth probes and style of depiction

Author

Van Doorn, A.J. (author), Koenderink, J.J. (author), Leyssen, M.H.R. (author), Wagemans, J. (author), Van Doorn, A.J. (author), Koenderink, J.J. (author), Leyssen, M.H.R. (author), and Wagemans, J. (author)

Abstract

We study the effect of stylistic differences on the nature of pictorial spaces as they appear to an observer when looking into a picture. Four pictures chosen from diverse styles of depiction were studied by 2 different methods. Each method addresses pictorial depth but draws on a different bouquet of depth cues. We find that the depth structures are very similar for 8 observers, apart from an idiosyncratic depth scaling (up to a factor of 3). The differences between observers generalize over (very different) pictures and (very different) methods. They are apparently characteristic of the person. The differences between depths as sampled by the 2 methods depend upon the style of the picture. This is the case for all observers except one., Industrial Design, Industrial Design Engineering

Published
2012
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147. Integrating biological motion: The role of grouping in the perception of point-light actions

Author

Poljac, E., Verfaillie, K., Wagemans, J., Poljac, E., Verfaillie, K., and Wagemans, J.

Abstract

Contains fulltext : 130332.pdf (publisher's version ) (Open Access), The human visual system is highly sensitive to biological motion and manages to organize even a highly reduced point-light stimulus into a vivid percept of human action. The current study investigated to what extent the origin of this saliency of point-light displays is related to its intrinsic Gestalt qualities. In particular, we studied whether biological motion perception is facilitated when the elements can be grouped according to good continuation and similarity as Gestalt principles of perceptual organization. We found that both grouping principles enhanced biological motion perception but their effects differed when stimuli were inverted. These results provide evidence that Gestalt principles of good continuity and similarity also apply to more complex and dynamic meaningful stimuli.

Published
2011

148. Measuring 3D point configurations in pictorial space

Author

Wagemans, J. (author), Van Doorn, A.J. (author), Koenderink, J.J. (author), Wagemans, J. (author), Van Doorn, A.J. (author), and Koenderink, J.J. (author)

Abstract

We propose a novel method to probe the depth structure of the pictorial space evoked by paintings. The method involves an exocentric pointing paradigm that allows one to find the slope of the geodesic connection between any pair of points in pictorial space. Since the locations of the points in the picture plane are known, this immediately yields the depth difference between the points. A set of depth differences between all pairs of points from an N-point (N > 2) configuration then yields the configuration in depth up to an arbitrary depth offset. Since an N-point configuration implies N(N_1) (ordered) pairs, the number of observations typically far exceeds the number of inferred depths. This yields a powerful check on the geometrical consistency of the results. We report that the remaining inconsistencies are fully accounted for by the spread encountered in repeated observations. This implies that the concept of 'pictorial space' indeed has an empirical significance. The method is analyzed and empirically verified in considerable detail. We report large quantitative interobserver differences, though the results of all observers agree modulo a certain affine transformation that describes the basic cue ambiguities. This is expected on the basis of a formal analysis of monocular optical structure. The method will prove useful in a variety of potential applications., Industrial Design, Industrial Design Engineering

Published
2011
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149. Space perception in pictures

Author

Van Doorn, A.J. (author), Wagemans, J. (author), De Ridder, H. (author), Koenderink, J.J. (author), Van Doorn, A.J. (author), Wagemans, J. (author), De Ridder, H. (author), and Koenderink, J.J. (author)

Abstract

A "picture" is a at object covered with pigments in a certain pattern. Human observers, when looking "into" a picture (photograph, painting, drawing, . . . say) often report to experience a three dimensional "pictorial space." This space is a mental entity, apparently triggered by so called pictorial cues. The latter are sub-structures of color patterns that are pre-consciously designated by the observer as "cues," and that are often considered to play a crucial role in the construction of pictorial space. In the case of the visual arts these structures are often introduced by the artist with the intention to trigger certain experiences in prospective viewers, whereas in the case of photographs the intentionality is limited to the viewer. We have explored various methods to operationalize geometrical properties, typically relative to some observer perspective. Here "perspective" is to be understood in a very general, not necessarily geometric sense, akin to Gombrich's "beholder's share". Examples include pictorial depth, either in a metrical, or a mere ordinal sense. We find that different observers tend to agree remarkably well on ordinal relations, but show dramatic differences in metrical relations., Industrial Design, Industrial Design Engineering

Published
2011
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150. Depth

Author

Koenderink, J.J. (author), Van Doorn, A.J. (author), Wagemans, J. (author), Koenderink, J.J. (author), Van Doorn, A.J. (author), and Wagemans, J. (author)

Abstract

Depth is the feeling of remoteness, or separateness, that accompanies awareness in human modalities like vision and audition. In specific cases depths can be graded on an ordinal scale, or even measured quantitatively on an interval scale. In the case of pictorial vision this is complicated by the fact that human observers often appear to apply mental transformations that involve depths in distinct visual directions. This implies that a comparison of empirically determined depths between observers involves pictorial space as an integral entity, whereas comparing pictorial depths as such is meaningless. We describe the formal structure of pictorial space purely in the phenomenological domain, without taking recourse to the theories of optics which properly apply to physical space—a distinct ontological domain. We introduce a number of general ways to design and implement methods of geodesy in pictorial space, and discuss some basic problems associated with such measurements. We deal mainly with conceptual issues., Design Engineering, Industrial Design Engineering

Published
2011
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