Virtual Reality Simulators for Inclusion and Participation: Broadening Perspectives on Accessible Cities and Public Space

The design of urban public space often involves a convergence of different actors with different priorities in the use of available space. This becomes evident when different modes of transport are combined in the very limited space available. At the same time, the growing and aging population strengthens demands for action in public space design towards better accessibility and involvement of the vulnerable. Innovations in digital design and simulation tools have shown a great demand to address these challenges as they have the potential to facilitate mediation and improve citizen science, participative and collaborative planning processes. Joint evaluation is supported and planners, decision makers and foremost citizens are brought together [(Yang et al. 2019), (Sanchez-Sepulveda et al. 2019), (Buffel et al. 2012)]. In our research, we have implemented human-computer interfaces for urban digital twins. These digital twins combine geometry and point cloud models, simulation results, and sensor data and enable analysis of existing situations, scenario testing, as well as prediction, on all urban scales, from buildings to cities and regions. By visualization in VR environments such as a CAVE (Cave Automatic Virtual Environment) they provide a powerful method for informed discussions between all stakeholders which is essential for joint decision-making. Our recent work extends these tools to include often neglected groups, such as people with disabilities, the elderly, or children, with the aim to empower them and to address their specific needs with respect to public spaces, while making these needs more traceable for others. Therefore, we have implemented different modes of traffic in simulators: Cars, bicycles, skateboards, and wheelchairs. Using one of these simulators, users can then interactively explore virtual replicas of public spaces using a real vehicle for steering. In combination with a tracking system, the user’s perspective in the virtual world is adjusted accordingly, enabling an impression of riding through the replica similar as in a real environment. Users can explore the accessibility of public spaces and detect shortcomings like high curbs or slopes. Often, these are unnoticed by pedestrians while posing major obstacles for people in wheelchairs, with strollers or roller walkers. Hence, this simulator helps to better understand and include the mentioned group in public participation. Moreover, the simulator was combined with traffic simulations (Zeile et al. 2021). These, in particular when visualized along with the digital twin, improve the depiction of the actual processes and dynamic scenarios, and allow to simulate and compare scenarios of different design proposals. Bottlenecks such as narrow sidewalks incapable of handling the load of pedestrians, or unclear intersections with an insufficient view can be detected as well as the use of space in certain conditions as during rush hours or at construction sites. Experiments were carried out using the different simulators as human-computer interfaces. Observations and questionnaires were used to analyse the experiences of 23 test subjects. In summary, the developed simulators are intended to contribute to safer and better accessible urban spaces for all. In this initial work, the focus lies on groups with special needs in public spaces - for example, highly mobile young people and in contrast people with limited mobility or the elderly. By detecting current barriers, the developed simulators make them tangible and understandable for the wider public but also for planners, designers, and decision-makers

Systematic Optimization of a Fragment-Based Force Field against Experimental Pure-Liquid Properties Considering Large Compound Families: Application to Saturated Haloalkanes

Direct optimization against experimental condensed-phase properties concerning small organic molecules still represents the most reliable way to calibrate the empirical parameters of a force field. However, compared to a corresponding calibration against quantum-mechanical (QM) calculations concerning isolated molecules, this approach is typically very tedious and time-consuming. The present article describes an integrated scheme for the automated refinement of force-field parameters against experimental condensed-phase data, considering entire classes of organic molecules constructed using a fragment library via combinatorial isomer enumeration. The main steps of the scheme, referred to as CombiFF, are as follows: (i) definition of a molecule family; (ii) combinatorial enumeration of all isomers; (iii) query for experimental data; (iv) automatic construction of the molecular topologies by fragment assembly; and (v) iterative refinement of the force-field parameters considering the entire family. As a first application, CombiFF is used here to design a GROMOS-compatible united-atom force field for the saturated acyclic haloalkane family. This force field relies on an electronegativity-equalization scheme for the atomic partial charges and involves no specific terms for σ-holes and halogen bonding. A total of 749 experimental liquid densities ρliq and vaporization enthalpies ΔHvap concerning 486 haloalkanes are considered for calibration and validation. The resulting root-mean-square deviations from experiment are 49.8 (27.6) kg·m–3 for ρliq and 2.7 (1.8) kJ·mol–1 for ΔHvap for the calibration (validation) set. The values are lower for the validation set which contains larger molecules (stronger influence of purely aliphatic interactions). The trends in the optimized parameters along the halogen series and across the compound family are in line with chemical intuition based on considerations related to size, polarizability, softness, electronegativity, induction, and hyperconjugation. This observation is particularly remarkable considering that the force-field calibration did not involve any QM calculation. Once the time-consuming task of target-data selection/curation has been performed, the optimization of a force field only takes a few days. As a result, CombiFF enables an easy assessment of the consequences of functional-form decisions on the accuracy of a force field at an optimal level of parametrization.ISSN:1549-9618ISSN:1549-962