Laboratoire Angevin de Mécanique, Procédés et InnovAtion

International audience

Current design of virtual reality (VR) applications relies essentially on the transposition of users' viewpoint in first-person perspective (1PP). Within this context, our research aims to compare the impact and the potentialities enabled via the integration of the third-person perspective (3PP) in immersive virtual environments (IVE). Our empirical study is conducted in order to assess the sense of presence, the sense of embodiment and performance of users confronted with a series of tasks presenting a case of potential use for the video game industry. Our results do not reveal significant differences concerning the sense of spatial presence with either point of view. Nonetheless, they provide evidence confirming the relevance of using the first-person perspective to induce a sense of embodiment toward a virtual body, especially in terms of self-location and ownership. However, no significant differences were observed concerning the sense of agency. Concerning users' performance, our results demonstrate that the first-person perspective enables more accurate interactions, while the third-person perspective provides better space awareness.

There are increasing new advances in virtual reality technologies as well as a rise in immersive virtual environments research and user experience research. Within this framework, we decided to address the overall user experience in immersive virtual environments. Indeed, in our point of view, this topic is not fully dealt with in the scientific literature, neither in terms of user experience components nor in terms of user experience measurement methods. It is in this context that we conducted a study aiming at proposing and validating a unified questionnaire on user experience in immersive virtual environment(IVEQ). Our questionnaire contains 10 subscales measuring presence, engagement, immersion, flow, usability, skill, emotion, experience consequence, judgement and technology adoption. The construction of our questionnaire was based on existing ones. It was tested on 116 participants after they use the edutainment virtual environment "Think and Shoot". Results show that 9 out of 10 subscales and 68 out of 87 items are reliable as demonstrated by an internal consistency analysis with Cronbach's alpha and an item analysis. Findings also indicate that the scale scores from 6 subscales are considered normal distributed (e.g. presence) whereas the scale scores from 3 subscales are considered negatively skewed (e.g. skill). This study provides important new insight into UX in IVEs assessment.

Selective Laser Melting (SLM) and Electron Beam Melting (EBM) are powder bed fusion processing which allows to build-up parts by successive addition of layers using 3D-CAD models. Among the advantages, are the high degree of freedom for part design and the small loss of material, which explain the increase of Ti-6Al-4V parts obtained by these processes. However, Ti-6Al-4V parts produced by SLM and EBM contain defects (surface roughness, porosity, tensile residual stresses) which decrease significantly the High Cycle Fatigue (HCF) life. In order to minimize the porosity and tensile residual stresses, post-processing treatments like Hot Isostatic Pressing (HIP) and Stress Relieving are often conducted. But the modification of the surface roughness by machining is very costly and not always possible, especially for parts with complex design. The aim of this work is to evaluate the effect of the surface roughness and microstructure of Ti-6Al-4V parts produced by SLM and EBM on the HCF life. Five sets of specimens were tested in tension-compression (R=-1; f=120Hz): Hot-Rolled (reference); SLM HIP machined; SLM HIP As-Built; EBM HIP machined; EBM HIP As-Built. For each condition, microstructure characterization, observation of the fracture surface of broken specimens and surface analysis were carried out respectively by Optical Microscope (OM), Scanning Electron Microscope (SEM) and 3D optical profilometer. Results of fatigue testing show a significant decrease of the HCF life mainly due to the surface roughness. Along with experimental testing, numerical simulations using FEM were conducted using the surface scans obtained by profilometry. Based on extreme values statistics of the crossland equivalent stress averaged on a critical distance, a methodology is proposed to take into account the effect of the surface roughness on the HCF life.

Most of the models of User eXperience (UX) in Immersive Virtual Environment (IVE) are partial due to the components and the measuring methods they suggest. We have presented in a previous work a holistic UX in IVE model, combining key components and influencing factors from the most common fields of Virtual Reality (education, entertainment and edutainment). We do not doubt that the best way to measure the UX in IVEs is to gather and compare results from the appropriate subjective methods with the appropriate objective methods. Nevertheless, in this paper, we chose to focus only on the questionnaire method. Indeed, most of components can be measured through questionnaires. The objective of this paper is to rely on the components of our UX model to select appropriate existing questionnaires and finally choose the more suitable items to create our own mixed questionnaire. First, this paper reviews the questionnaires chosen to create our own. Finally, it proposes an elaboration of the final questionnaire.

There are increasing new advances in virtual reality technologies as well as a rise in learning virtual environments for which several studies highlighted the pedagogical value, knowledge transfer, and learners’ engaged-behaviors. Moreover, the notion of user experience is now abundant in the scientific literature without the fact that there are specific models for immersive environments. This paper aims at proposing and validating a model of User eXperience in Immersive Virtual Environment, including virtual learning environments. The model is composed of 10 components extracted from existing models (i.e., presence, engagement, immersion, flow, usability, skill, emotion, experience consequence, judgement, and technology adoption). It was validated in a user study involving 152 participants who were asked to use the edutainment application Think and Shoot and to complete an immersive virtual environment questionnaire. The findings lead us to a modified user experience model questioning new paths between user experience components (e.g., the influence of experience consequence on flow).

This study presents the second phase of a series of experiments investigating the impact of avatar visual fidelity on the sense of embodiment and users' behavior in immersive virtual environments. Our main focus concerns the similarity between users and avatars, a factor known as truthfulness. Our experiment requires the participants to control three avatars using a third-person perspective: a robot, a suit and their virtual doppelganger (virtual representation of the self). In order to analyze users' reactions and strategies, each task of the scenario of the virtual reality application can potentially affect the integrity of their characters. Our results revealed that ownership, one of the three factors of the sense of embodiment, is higher for the participants controlling their self-representation than with abstract representations. Furthermore, avatar visual fidelity seems to affect users' subjective experience, half of the panel reported having different behavior depending on the controlled character. Abstract representations allow the users to adopt more risky behaviors, while self-representations maintain a connection with the real world and encourage users to preserve the integrity of their avatar.

Sparse model identification by means of data is especially cumbersome if the sought dynamics live in a high dimensional space. This usually involves the need for large amount of data, unfeasible in such a high dimensional settings. This well‐known phenomenon, coined as the curse of dimensionality, is here overcome by means of the use of separate representations. We present a technique based on the same principles of the Proper Generalized Decomposition that enables the identification of complex laws in the low‐data limit. We provide examples on the performance of the technique in up to ten dimensions.

In recent years, technologies have evolved towards social, universal and collaborative uses involving multiple users. However, methods and models from user centered design are focused on single-user design and do not take into account the impact of other users on intentions and behaviors to use the technology. The objective of this article is to provide paths of reflection on how to integrate a multi-user centered approach to existing user centered design methods and models. Each phase of user-centered design has been rethought to implement this new framework. Guidelines for moving from user experience to Multi-User eXperience (MUX) are provided. In the same way, we recommend adding a multi-user variable in the technology acceptance models to become the Multi-user Acceptance Model (MAM). User research and user testing have also been rethought to a multi-user reach and a multi-user testing. All these considerations are discussed, and lead to a proposal of a future Multi-user Centered Design (MCD) approach, specifically adapted to manage multi-user digital technology development projects. Finally, it is therefore necessary and important to direct research in the fields (acceptance, user experience, user research and user testing) to assist designers with the development of new methods of product design more respectful of social, environmental and collaborative values.

Laser Doppler flowmetry signals give information about many physiological activities of the cardiovascular system. The activities manifest themselves in rhythmic cycles. In order to explore these activities during the reactive hyperemia phenomenon, a novel time-frequency method, called the S-transform, based on a scalable Gaussian wavelet, is applied. The goal is to have a deeper understanding of reactive hyperemia. This paper focuses on the evaluation of the different activities between a rest signal and an hyperemia signal, both acquired simultaneously on the two forearms of healthy subjects. The results show that after the release of the occlusion, the myogenic, neurogenic, and endothelial related activities clearly increase on the forearm where the occlusion took place. Then, they return progressively to their basal level. However, on the rest forearm, no increase is noted for the three activities. The mechanisms that take place during reactive hyperemia are, therefore, local. The S-transform proves to be a suited time-frequency method, in order to analyze laser Doppler signal underlying mechanisms.

Abstract In this paper the coupling of a parabolic model with a system of local kinetic equations is analyzed. A space–time separated representation is proposed for the global model (this is simply the radial approximation proposed by Pierre Ladeveze in the LATIN framework ( Non‐linear Computational Structural Mechanics . Springer: New York, 1999)). The originality of the present work concerns the treatment of the local problem, that is first globalized (in space and time) and then fully globalized by introducing a new coordinate related to the different species involved in the kinetic model. Thanks to the non‐incremental nature of both discrete descriptions (the local and the global one) the coupling is quite simple and no special difficulties are encountered by using heterogeneous time integrations. Copyright © 2009 John Wiley & Sons, Ltd.

Piloting a manual wheelchair is an important necessity for the everyday life and social activities of people with physical and sometimes cognitive disabilities. It requires complex capacities and may become tiring and stressful during indoor as well

The present paper aims to study the effect of manufacturing build orientation on both flexural quasi-static and fatigue behaviours of semi-crystalline polyamide 6 obtained by Fused Filament Fabrication (FFF), by considering the porosity and surface roughness. The glass transition temperature, melting temperature, and crystallinity degree were measured complementary to understand better the process. Fatigue analysis is here fully described in visco-elastic domain of material. The results highlight that the XZ build orientation is better than the XY one and suggest that porosity plays an important role. The obtained results are also compared with conventional techniques given by the literature review.

Classifying the many types of video games is difficult, as their genres and supports are different, but they all have in common that they seek the commitment of the player through exciting emotions and challenges. Since the income of the video game industry exceeds that of the film industry, the field of inducting emotions through video games and virtual environments is attracting more attention. Our theory, widely supported by substantial literature, is that the chromatic stimuli intensity, brightness, and saturation of a video game environment produce an emotional effect on players. We have observed a correlation between the RGB additives color spaces, HSV, HSL, and HSI components of video game images, presented to<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mi>n</mml:mi><mml:mo>=</mml:mo><mml:mn fontstyle="italic">85</mml:mn></mml:math>participants, and the emotional statements expressed in terms of arousal and valence, recovered in a subjective semantic questionnaire. Our results show a significant correlation between luminance, saturation, lightness, and the emotions of joy, sadness, fear, and serenity experienced by participants viewing 24 video game images. We also show strong correlations between the colorimetric diversity, saliency volume, and stimuli conspicuity and the emotions expressed by the players. These results allow us to propose video game environment development methods in the form of a circumplex model. It is aimed at game designers for developing emotional color scripting.

The sense of "Presence" (evolving from "telepresence") has always been associated with virtual reality research and is still an exceptionally mystifying constituent. Now the study of presence clearly spans over various disciplines associated with cognition. This paper attempts to put forth a concept that argues that it's an experience of an "Evoked Reality (ER)" (illusion of reality) that triggers an "Evoked Presence (EP)" (sense of presence) in our minds. A Three Pole Reality Model is proposed to explain this phenomenon. The poles range from Dream Reality to Simulated Reality with Primary (Physical) Reality at the center. To demonstrate the relationship between ER and EP, a Reality-Presence Map is developed. We believe that this concept of ER and the proposed model may have significant applications in the study of presence, and in exploring the possibilities of not just virtual reality but also what we call "reality."

The mevalonate kinase deficiency (MKD), including hyperimmunoglobulinemia D periodic fever syndrome (HIDS) and the more severe mevalonic aciduria are rare, autosomal recessive, autoinflammatory diseases belonging to the hereditary periodic fever (HPF) family. Other members include: familial mediterranean fever (FMF), the cryopyrin-associated periodic syndromes (CAPS) and TNFR-associated periodic syndromes (TRAPS). MKD is caused by mutations in the gene encoding mevalonate kinase (MK), an enzyme of the cholesterol pathway, leading to its inactivation. The molecular mechanisms linking MKD and abnormalities of isoprenoid biosynthesis to cytokine production and inflammation have yet to be fully elucidated. Statins, which are extensively prescribed for lowering cholesterol, are potent inhibitors of 3-hydroxy-3-methylglutaryl-CoA reductase, the enzyme directly upstream of MK. In this review, we discuss recent reports demonstrating that in vitro inhibition of the mevalonate pathway by statins specifically increases the production, by activated monocytes, of cytokines of the IL-1 family, by enhancing caspase-1 activity, the enzyme responsible for IL-1beta and IL-18 maturation. The molecular mechanisms involve geranylgeranylation and the enhancement of the activity of G proteins such as Rac-1. Interestingly, activated fibroblasts from MKD patients secrete more IL-1beta than fibroblasts from healthy donors. Taken together, these data highlight the specific enhancement of the IL-1 family of cytokines, the maturation of which is caspase-1-dependent in MKD. Finally, the spectacular decrease in febrile attacks in patients with severe HIDS under IL-1 receptor antagonist (anakinra) treatment, reinforces this hypothesis. Deregulated caspase-1 activation could be responsible for the inflammatory component of MKD, thereby mechanistically linking MKD to FMF and CAPS through cytokines of the IL-1 family.

Additive manufacturing of polymer products over the past decade has become widespread in various areas of industry. Using the fused filament fabrication (FFF) method, one of the most technologically simple methods of additive manufacturing, it is possible to produce parts from a large number of different materials, including wear-resistant nylon. The novelty of the work is properties investigation of ±45° filling configuration with different filling degree for nylon, as well as calculating the effect of infill on the strength characteristics, excluding the shell. This article reflects the process of manufacturing samples from nylon using FFF technology with various internal topologies, as well as tensile tests. The analysis of the obtained results is performed and the relationship between the structure of the sample and the limit of its strength is established. To calculate real filling degree and the effect of internal filling on the strength characteristics of the specimen, it is proposed to use a method based on the geometric and mass parameters. The FFF method is promising for developing methods for producing a composite material. The results of this article can be useful in choosing the necessary manufacturing parameters.

The corrosion resistance of magnesium alloys depends mainly on its surface integrity. Previous experimental studies have shown that machining can induces small (nano-scale) grain size, compressive residual stresses and basal plane crystallographic texture, which significantly improve the corrosion resistance of magnesium alloy. These studies have focused on the positive effects of cryogenic cooling and tool edge radius preparation. In this paper, the influence of a wide range of cutting process parameters (including cut-ting speed, feed, tool rake angle, tool edge radius and cooling conditions) acting on the cutting mechanics and surface integrity produced during machining of AZ31B-O magnesium alloy have been studied experimentally and numerically.

OBJECTIVE: To evaluate whether visual cues are helpful for virtual spatial navigation and memory in Alzheimer's disease (AD) and patients with mild cognitive impairment (MCI). METHOD: 20 patients with AD, 18 patients with MCI and 20 age-matched healthy controls (HC) were included. Participants had to actively reproduce a path that included 5 intersections with one landmark at each intersection that they had seen previously during a learning phase. Three cueing conditions for navigation were offered: salient landmarks, directional arrows and a map. A path without additional visual stimuli served as control condition. Navigation time and number of trajectory mistakes were recorded. RESULTS: With the presence of directional arrows, no significant difference was found between groups concerning the number of trajectory mistakes and navigation time. The number of trajectory mistakes did not differ significantly between patients with AD and patients with MCI on the path with arrows, the path with salient landmarks and the path with a map. There were significant correlations between the number of trajectory mistakes under the arrow condition and executive tests, and between the number of trajectory mistakes under the salient landmark condition and memory tests. CONCLUSION: Visual cueing such as directional arrows and salient landmarks appears helpful for spatial navigation and memory tasks in patients with AD and patients with MCI. This study opens new research avenues for neuro-rehabilitation, such as the use of augmented reality in real-life settings to support the navigational capabilities of patients with MCI and patients with AD. (PsycINFO Database Record

Abstract In metal cutting a large amount of the external energy supplied to the cutting system is converted into heat. Therefore, the study of the thermal phenomenon developed in the metal cutting process is of prime concern. This phenomenon has a great influence on many metal cutting variables as tool wear, residual stress, and part distortion. This article presents the experimental analysis of the temperature distribution in the three-dimensional cutting process. Specially designed thermal imaging equipment, included both hardware and software, was developed in order to determine the temperature distribution in the deformation zone. A detailed description of this equipment, its calibration procedure and a full analysis of the emissivity of the cutting system components (chip, tool, and workpiece) are discussed. The designed thermal imaging equipment was proven to be very powerful to analyze the influence of the cutting parameters (cutting speed, cutting feed, depth of cut, work material, tool geometry, and tool material) on this temperature distribution. This equipment can also be useful for the construction and validation of numerical and analytical models of the three-dimensional cutting process.