Explore the vast range of titles available.

A bstract Predicting the rate for μ → e conversion in nuclei for a given set of effective operators mediating the violation of lepton flavor symmetry crucially depends on hadronic and nuclear matrix elements. In particular, the uncertainties inherent in this non-perturbative input limit the discriminating power that can be achieved among operators by studying different target isotopes. In order to quantify the associated uncertainties, as a first step, we go back to nuclear charge densities and propagate the uncertainties from electron scattering data for a range of isotopes relevant for μ → e conversion in nuclei, including 40 , 48 Ca, 48 , 50 Ti, and 27 Al. We provide as central results Fourier-Bessel expansions of the corresponding charge distributions with complete covariance matrices, accounting for Coulomb-distortion effects in a self-consistent manner throughout the calculation. As an application, we evaluate the overlap integrals for μ → e conversion mediated by dipole operators. In combination with modern ab-initio methods, our results will allow for the evaluation of general μ → e conversion rates with quantified uncertainties.

The Lake Chad region is facing a nexus of interconnected problems including fragility, violent conflict, forced displacement, and scarcity of water and other resources, further aggravated by climate change. Focusing on northeast Nigeria, this study aims to answer the following questions: (1) What role does access to water and farming play in out-migration and return in northeast Nigeria? (2) What is the potential of tensions between internally displaced persons (IDPs) and host communities? Data for this study were collected between March and May 2019 by interviewing 304 local residents and IDPs in northeast Nigeria, as well as experts on migration, environmental, humanitarian and conflict-related issues in research centers and governmental institutions in Abuja. Given the pronounced water scarcity in the region, the results show that between 47% and 95% of rural community members interviewed in northeast Nigeria would be willing to migrate in cases of water scarcity. At the time of study, only 2.5% to 7% of respondents had migrated previously in response to water scarcity, indicating that insecurity and conflict were, however, more relevant drivers of displacement. Regarding our second research question, we find a potential for tensions between IDPs and host communities, as 85% of the interviewed host community members oppose the presence of the IDPs. Hence, measures are needed to improve relations between the two groups. In order to avoid a future scenario where water scarcity becomes a significant driver of migration, efficient management of water resources is paramount. Such action would not only address the issue of migration, but also strengthen the resilience of communities in northern Nigeria.

The birth of the approach Model-Based System Engineering (MBSE) with a paradigm transition from document-based to model-based aims to improve the system architect activities. However, the methods and tools of this approach are inherited from software engineering, leading to various difficulties, such as the need for dispersed information in different views and models, increased complexity in human-model interactions for modelling tasks, highly codified data with domain-specific languages, substantial volume of data with esoteric diagrammatic representations, etc. Those difficulties make the adoption in the practice field extremely challenging. Virtual Reality (VR), on the other hand, offers interaction methods that are close to those used in the real world. Thus, the VR technology could address those challenges by integrating the possibility of having one complete immersive virtual environment encompassing all the presentations of different points of view, with more intuitive interactions with models. Consequently, this paper proposes a new human-centric MBSE modelling environment using 3D visuals, with the objective of an intuitive and complete environment to ease the collaboration of interdisciplinary co-design tasks in systems engineering. Formative usability tests with 3 groups of experts from different disciplines are conducted with a questionnaire and an interview with open questions. The overall evaluation of the user experience with the immersive virtual environment was very positive. Experts demonstrated great interest in the environments for easier-to-understand representations, more ludic user experience, and improvements in the co-conception activities. More experiments with quantitative analysis will be conducted for the next step, and future studies will focus on extending the proposed modelling environment for symmetric/asymmetric collaboration and complex industrial product-process systems.

In this study, we aim to analyze social networks in which internally displaced persons (IDPs) are involved in northeast Nigeria, after they have been displaced by the insurgency of the Boko Haram group. While IDPs usually resettle in camps operated by the government, contacts with host communities are common. We further analyze the potential that such contacts may lead to conflicts between IDPs and their host communities in the Lake Chad region. Data for this study were collected by interviewing IDPs in the Bakassi IDP camp in Maiduguri and by interviewing members of the host community in Maiduguri in close proximity to the Bakassi IDP camp. A Social Network Analysis approach was used to analyze the data, by constructing social network graphs and computing network attributes, mainly the betweenness centrality of actors. The results of the study show on the one hand a mixture of friendly and conflicting relationships between IDPs and the host community from the IDPs’ perspective, and on the other hand, only few contacts between members of the host community and IDPs in the Bakassi IDP camp, from the host community's perspective. The analysis suggests that in the context of conflict present in the Lake Chad region, IDPs and members of the host community mainly use closed networks, to keep available resources and economic opportunities within their communities. We recommend a better service delivery to IDPs but also to members of the host communities who feel neglected as more attention is given to IDPs with the distribution of humanitarian aid.

For almost two decades, the Lake Chad Basin (LCB) in general and northeast Nigeria in particular have been subject to the insurgency of the Islamist terrorist group Boko Haram. This region is also known for its poor environmental conditions that mostly manifest in land desertification and water scarcity. We analyze the impact of the insecurity and conflict on migration from the most affected rural areas of northeast Nigeria to Maiduguri. We also explore the role that water scarcity and land desertification play in the decision of local people to migrate. Data were collected by interviewing 204 internally displaced persons (IDPs) at the Bakassi IDP camp in Maiduguri between March and May 2019. Experts were also interviewed at various governmental, non-governmental, and international institutions in Abuja. Respondents at the Bakassi IDP camp came from Guzamala, Gwoza, Marte, Monguno, and Nganzai. Though insecurity created by the conflict between Boko Haram insurgents and government forces was mentioned by all respondents as the main factor that triggered migration, this study shows that the decision to migrate was also a function of other factors that differ between communities. These factors include the geographical location of the community, land ownership, the socioeconomic status of the migrants, access to water and land, and wealth. This study reveals that in some communities, it was possible for people to live with conflict if they were still able to practice farming or if they had additional sources of income such as small businesses. The decision to migrate was only taken when the practice of such activities was no longer possible and they had nothing to hold on to.

Virtual Reality (VR) technology has advanced forward in everyday life where virtual fitness is possible through physically moving around in the real world. Exergame is a video game for exercise aimed at making exercise more fun. VR exergame applies these trends together for virtual fitness with immersive game play. The VR locomotion is traveling in VR, which is commonly used in adventure role-playing games (RPG). Virtual running can be applied as a locomotion technique for VR exergames. The design of virtual running in VR exergames should be considered as an exercise for fitness and also for enjoyment. This paper proposed two motion-based locomotion techniques: ArmSwing and Squat for virtual running, which are considered as aerobic and strength exercise. These two postures were used to study how physical exertion affected players while interacting in the test scene. Usability, motion sickness, and enjoyment were assessed to analyze the differences of each posture. The results showed that motion sickness and enjoyment of ArmSwing and Squat were not different, while usability was different where ArmSwing was rated higher than Squat. The results from the interviews suggest that most players preferred aerobic exercise (ArmSwing) more than strength exercise (Squat) for a long period of exercise. However, for a short period of exercise, players preferred strength exercise more than aerobic exercise. The adventure-based RPG for exercise needs a solution design appropriate for virtual running in VR, and our results can be a guideline for developers in order to handle motion-based locomotion for VR exergames.

Product development involves many experts collaborating to the same design goal. Every expert has his own formalisms and tools leading to a high heterogeneity of information systems supporting design activities. Interoperability became a major challenge to avoid information incompatibility along the product life cycle. To synchronise heterogeneous representations of product will be a major step to integrate expert activities. In this paper, the authors propose a meta-model framework to connect together heterogeneous design models. This meta-model framework is used to formalise possible interactions between heterogeneous representations. Interaction formalisation is considered as a key point to synchronise heterogeneous models and to provide more interoperability between various computer assisted systems. The synchronisation loop is also presented as a major sequence of activities to manage collaborative design. Tools to support synchronisation are proposed. However, through a basic case study, authors highlight what can be automated and where human intervention is still expected.

A new application for virtually simulating assembly tasks was developed by integrating multimodal data and kinematic information provided by a mobility module into a Collaborative Virtual Environment. During assembly simulations, the haptic device implemented in the application supports the user’s movements by using the automatically detected kinematic constraints between the components of the assembly. Thus, all stages of the assembly process can be simulated, which leads to an increase of the user immersion. The current paper presents the methodology, the protocols and the results of evaluating the application, the test being performed by a group of 20 participants. Tasks were run for assessing the following criteria: usability, efficiency, ease of use and quality of the haptic feedback. Each participant tested the application for two types of assemblies (mounting flange and standard vise) with different complexity and number of components. Testing protocols considered both objective evaluation (using real-time information), as well as subjective evaluation using questionnaires. The analysis of the results proved the feasibility of the proposed approach. Further work will be focused on extensive studies for assessing intra-users variations and improvement of the haptic feedback for a number of particular situations reported by users as important.

Virtual Reality (VR) technology is frequently applied in simulation, particularly in medical training. VR medical training often requires user input either from controllers or free-hand gestures. Nowadays, hand gestures are commonly tracked via built-in cameras from a VR headset. Like controllers, hand tracking can be used in VR applications to control virtual objects. This research developed VR intubation training as a case study and applied controllers and hand tracking for four interactions—namely collision, grabbing, pressing, and release. The quasi-experimental design assigned 30 medical students in clinical training to investigate the differences between using VR controller and hand tracking in medical interactions. The subjects were divided into two groups, one with VR controllers and the other with VR hand tracking, to study the interaction time and user satisfaction in seven procedures. System Usability Scale (SUS) and User Satisfaction Evaluation Questionnaire (USEQ) were used to measure user usability and satisfaction, respectively. The results showed that the interaction time of each procedure was not different. Similarly, according to SUS and USEQ scores, satisfaction and usability were also not different. Therefore, in VR intubation training, using hand tracking has no difference in results to using controllers. As medical training with free-hand gestures is more natural for real-world situations, hand tracking will play an important role as user input for VR medical training. This allows trainees to recognize and correct their postures intuitively, which is more beneficial for self-learning and practicing.

PurposeThe paper aims to present the processing pipeline of an assembly immersive simulation application which can manage the interaction between the virtual scene and user using stereoscopic display and haptic devices. A new set of elements are integrated in a Collaborative Virtual Environment (CVE) and validated using an approach based on subjective and objective users’ performance criteria. The developed application is intended for Assembly/Disassembly (A/D) analysis, planning and training.Design/methodology/approachA mobility module based on contact information is used to handle the assembly components’ movements through real-time management of collision detection and kinematically constraint guidance. Information on CVE architecture, modules and application configuration process are presented. Impact of device type (3 degrees of freedom (DoFs) vs 6 DoFs) over user’s experience is evaluated. Parameters (number of assembled components and components assembly time) are measured for each user and each haptic device, and results are compared and discussed.FindingsTest results proved the efficiency of using a mobility module based on predefined kinematic constraints for reducing the complexity of collision detection algorithms in real-time assembly haptic simulations. Also, experiments showed that, generally, users performed better with 3 DoFs haptic device compared to 6 DoFs haptic equipment.Originality/valueThe proposed immersive application automates the kinematical joints inference from 3D computer-aided design (CAD) assembly models and integrates it within a haptic-based virtual environment, for increasing the efficiency of A/D process simulations.