This study examines attributes of virtual human behavior that may increase the plausibility of a simulated crowd and affect the user's experience in Virtual Reality. Purpose-developed experiments in both Immersive and semi-Immersive Virtual Reality systems queried the impact of collision and basic interaction between real-users and the virtual crowd and their effect on the apparent realism and ease of navigation within VR. Participants' behavior and subjective measurements indicated that facilitating collision avoidance between the user and the virtual crowd makes the virtual characters, the environment and the whole Virtual Reality system appear more realistic and lifelike. Adding basic social interaction, such as verbal salutations, gaze, and other gestures by the virtual characters towards the user, further contributes to this effect, with the participants reporting a stronger sense of presence. On the other hand, enabling collision avoidance on its own produces a reduced feeling of comfort and ease of navigation in VR. Objective measurements showed another interesting finding that collision avoidance may reduce the user's performance regarding their primary goal (navigating in VR following someone) and that this performance is further reduced when both collision avoidance and social interaction are facilitated.

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A key challenge in designing algorithms for leakage detection and isolation in drinking water distribution systems, is the performance evaluation and comparison between methodologies using benchmarks. For this purpose, the "Battle of the Leakage Detection and Isolation Methods" (Bat-tLeDIM) competition was organized in 2020 with the aim to objectively compare the performance of methods for the detection and localization of leakage events, relying on SCADA measurements of flow and pressure sensors installed within a virtual water distribution system. Several teams from academia and the industry submitted their solutions, using various techniques including time-series analysis, statistical methods, machine learning, mathematical programming, meta-heuristics and engineering judgment, and were evaluated using realistic economic criteria. This paper summarizes the results of the competition and conducts an analysis of the different leakage detection and isolation methods used by the teams. The competition results highlight the need for further development of methods for leakage detection and isolation, and also the need to develop additional open benchmark problems for this purpose. Vrachimis et al., May 24, 2022 network; and leakage localization, which aims to provide an approximate location of leakages given the available measurements. A recent review paper (Chan et al. 2018) classifies leakage detection methodologies into Passive and Active methods. Passive methods (also referred to as equipmentbased, hardware or external methods) require the deployment of specialized equipment, such as acoustic sensors or ground penetrating radars, at areas that are suspect of leakage. Active methods(also referred to as internal or software methods) are methods that are based on the presence of permanently installed sensors which continuously monitor the system for leakages. The latest developments in hydraulic sensor technology and on-line data acquisition systems have enabled water companies to deploy a larger number of more accurate pressure and flow devices with less cost. These data can be used to monitor the system in real-time and develop methodologies that use the data to detect and pre-localize leaks using Active methods. Pre-localization is the process of defining an area in which the leak exists, instead of pin-pointing exactly its location. This research area has witnessed a significant interest, as indicated in recent review papers (