Abstract
Developing and optimizing software applications for high performance and energy efficiency is a very challenging task, even when considering a single target machine. For instance, optimizing for multicore-based computing systems requires in-depth knowledge about programming languages, application programming interfaces (APIs), compilers, performance tuning tools, and computer architecture and organization. Many of the tasks of performance engineering methodologies require manual efforts and the use of different tools not always part of an integrated toolchain. This paper presents Pegasus, a performance engineering approach supported by a framework that consists of a source-to-source compiler, controlled and guided by strategies programmed in a Domain-Specific Language, and an autotuner. Pegasus is a holistic and versatile approach spanning various decision layers composing the software stack, and exploiting the system capabilities and workloads effectively through the use of runtime autotuning. The Pegasus approach helps developers by automating tasks regarding the efficient implementation of software applications in multicore computing systems. These tasks focus on application analysis, profiling, code transformations, and the integration of runtime autotuning. Pegasus allows developers to program their strategies or to automatically apply existing strategies to software applications in order to ensure the compliance of non-functional requirements, such as performance and energy efficiency. We show how to apply Pegasus and demonstrate its applicability and effectiveness in a complex case study, which includes tasks from a smart navigation system.

Abstract
Typical VR interactions can be tiring, including standing up, walking, and mid-air gestures. Such interactions result in decreased comfort and session duration compared with traditional non-VR interfaces, which may, in turn, reduce productivity. Nevertheless, current approaches often neglect this aspect, making the VR experience not as promising as it can be. As we see it, desk VR experiences provide the convenience and comfort of a desktop experience and the benefits of VR immersion, being a good compromise between the overall experience and ergonomics. In this work, we explore navigation techniques targeted at desk VR users, using both controllers and a large multi-touch surface. We address travel and orientation techniques independently, considering only continuous approaches for travel as these are better suited for exploration and both continuous and discrete approaches for orientation. Results revealed advantages for a continuous controller-based travel method and a trend for a dragging-based orientation technique. Also, we identified possible trends towards task focus affecting overall cybersickness symptomatology.

Abstract
Virtual reality (VR) technologies have been used successfully in tourism marketing. While most conventional VR applications are of an audiovisual nature, the constant evolution of these technologies allows providing enriched multisensory VR content that can further increase the potential of VR applied to the tourism field. To generate insights into the impact of such VR technologies, this manuscript investigates the impact of such multisensory VR setups and gender on the user's sense of presence, satisfaction, emotions, and attitudes. A user study with a gender-balanced sample (N = 80) was carried where two VR setups (audiovisual vs multisensory) were compared taking into account the user's gender. Results revealed that the female sample scored significantly higher spatial presence across VR setups and reported more involvement and overall presence in the audiovisual condition. In addition, correlations were found between the pairs Spatial Presence-Emotions, Spatial Presence-Enjoyment, Satisfaction-Involvement, Satisfaction-Enjoyment, and Satisfaction and Usefulness to perceive the destination. Results also suggest that multisensory stimulus can mitigate possible gender differences in passive VR scenarios. We concluded that the capability of the VR system to make users feel physically present in the virtual environment contributes significantly to the development of positive emotions and enjoyment, which can contribute positively to the user's consumer behaviour towards the touristic products and services.

Abstract
As blockchains go beyond cryptocurrencies into applications in multiple industries such as Insurance, Healthcare and Banking, handling personal or sensitive data, data access control becomes increasingly relevant. Access control mechanisms proposed so far are mostly based on requester identity, particularly for permissioned blockchain platforms, and are limited to binary, all-or-nothing access decisions. This is the case with Hyperledger Fabric's native access control mechanisms and, as permission updates require consensus, these fall short regarding the flexibility required to address GDPR-derived policies and client consent management. We propose SDAM, a novel access control mechanism for Fabric that enables fine-grained and dynamic control policies, using both contextual and resource attributes for decisions. Instead of binary results, decisions may also include mandatory data transformations as to conform with the expressed policy, all without modifications to Fabric. Results show that SDAM's overhead w.r.t baseline Fabric is acceptable. The scalability of the approach w.r.t to the number of concurrent clients is also evaluated and found to follow Fabric's.

Abstract

Abstract
Digital musical instruments have become increasingly prevalent in musical creation and production. Optimizing their usability and, particularly, their expressiveness, has become essential to their study and practice. The absence of multimodal feedback, present in traditional acoustic instruments, has been identified as an obstacle to complete performer-instrument interaction in particular due to the lack of embodied control. Mobile-based digital musical instruments present a particular case by natively providing the possibility of enriching basic auditory feedback with additional multimodal feedback. In the experiment presented in this article, we focused on using visual and haptic feedback to support and enrich auditory content to evaluate the impact on basic musical tasks (i.e., note pitch tuning accuracy and time). The experiment implemented a protocol based on presenting several musical note examples to participants and asking them to reproduce them, with their performance being compared between different multimodal feedback combinations. Collected results show that additional visual feedback was found to reduce user hesitation in pitch tuning, allowing users to reach the proximity of desired notes in less time. Nonetheless, neither visual nor haptic feedback was found to significantly impact pitch tuning time and accuracy compared to auditory-only feedback.