Anxiety symptoms are important contributors to the global health-related burden. Low-intensity interventions have been proposed to reduce anxiety symptoms in the population. Among these, biofeedback (BF) offers an effective approach to reducing anxiety. In the present study, BF was integrated into a novel virtual reality (VR) architecture to enhance BF's effectiveness to i) evaluate the feasibility of a VR-based single-session BF in teaching participants to self-regulate; ii) compare the BF aiming at reducing sympathetic (measured though the tonic level of skin conductance, SCL) versus increasing cardiac vagal (i.e., normalized high frequency of heart rate variability, HFnu-HRV) activation, and iii) evaluate which of the two VR-BF single-sessions was most effective in reducing perceived state anxiety. 20 healthy participants underwent both SCL- and HFnu-based in a single session VR-BF. Results showed the feasibility of a short single-session VR-BF and the effectiveness of both VR-BF sessions in reducing perceived state anxiety. Moreover, SCL-based VR-BF determined a significant reduction in sympathetic activation and in sympathovagal balance as well as a greater reduction in perceived state anxiety compared to HFnu-based VR-BF. SCL-based VR-BF represents a safe and effective intervention in reducing anxiety while enhancing adaptive psychophysiological activation.

The investigation of the physiological and pathological processes involved in fear perception is complicated due to the difficulties in reliably eliciting and measuring the complex construct of fear. This study proposes a novel approach to induce and measure subjective fear and its physiological correlates combining virtual reality (VR) with a mixed-effects model based on skin conductance (SC). Specifically, we developed a new VR scenario applying specific guidelines derived from horror movies and video games. Such a VR environment was used to induce fear in eighteen volunteers in an experimental protocol, including two relaxation scenarios and a neutral virtual environment. The SC signal was acquired throughout the experiment, and after each virtual scenario, the emotional state and fear perception level were assessed using psychometric scales. We statistically evaluated the greatest sympathetic activation induced by the fearful scenario compared to the others, showing significant results for most SC-derived features. Finally, we developed a rigorous mixed-effects model to explain the perceived fear as a function of the SC features. Model-fitting results showed a significant relationship between the fear perception scores and a combination of features extracted from both fast- and slow-varying SC components, proposing a novel solution for a more objective fear assessment.

Current capacity planning practices based on heavy over-provisioning of power infrastructure hurt (i) the operational costs of data centers as well as (ii) the computational work they can support. We explore a combination of statistical multiplexing techniques to improve the utilization of the power hierarchy within a data center. At the highest level of the power hierarchy, we employ controlled underprovisioning and over-booking of power needs of hosted workloads. At the lower levels, we introduce the novel notion of soft fuses to flexibly distribute provisioned power among hosted workloads based on their needs. Our techniques are built upon a measurement-driven profiling and prediction framework to characterize key statistical properties of the power needs of hosted workloads and their aggregates. We characterize the gains in terms of the amount of computational work (CPU cycles) per provisioned unit of power Computation per Provisioned Watt (CPW). Our technique is able to double the CPWoffered by a Power Distribution Unit (PDU) running the e-commerce benchmark TPC-W compared to conventional provisioning practices. Over-booking the PDU by 10% based on tails of power profiles yields a further improvement of 20%. Reactive techniques implemented on our Xen VMM-based servers dynamically modulate CPU DVFS states to ensure power draw below the limits imposed by soft fuses. Finally, information captured in our profiles also provide ways of controlling application performance degradation despite overbooking. The 95th percentile of TPC-W session response time only grew from 1.59 sec to 1.78 sec--a degradation of 12%.

Although Transmission Control Protocol (TCP) is a widely deployed and successful protocol, it shows some limitations in present-day environments. In particular, it is unable to exploit multiple (physical or logical) paths between two hosts. This paper presents PATTHEL, a session-layer solution designed for parallelizing stream data transfers. Parallelization is achieved by striping the data flow among multiple TCP channels. This solution does not require invasive changes to the networking stack and can be implemented entirely in user space. Moreover, it is flexible enough to suit several scenarios - e.g. it can be used to split a data transfer among multiple relays within a peer-to-peer overlay network.

Despite its efficiency, the general approach of hardcoding protocol format descriptions in packet processing applications suffers from many limitations. Among the others, the lack of flexibility when needing to extend the software for supporting new protocols, and the proliferation of modules with similar functionality between different applications, resulting in decreased maintainability. The NetPDL language was defined for overcoming such limitations, allowing decoupling applications from the knowledge of the format of protocol headers. The main criticism to NetPDL relates to its supposed performance penalties; this paper demonstrates that this language can be effectively used for the dynamic generation of optimized, i.e. efficient and fast, packet-processing code, and presents the architecture of a compiler implemented for such purpose.

With the ever increasing amount of traffic, scalability is probably the most important factor that differentiates several existing approaches to traffic classification. This paper focuses on payload-based classification and compares the results obtained through a "lightweight" traffic classification approach with the ones obtained with a "completely stateful" approach, demonstrating that the first approach, albeit less precise, is still appropriate for a large class of applications.

Despite the importance of traffic classification in modern networks, the number of languages tailored to this task is extremely limited. These languages can be valuable, because they allow the update of an application (e.g. firewall) in terms of supported protocols by simply updating its protocol description database, instead of recompiling the application from scratch. This paper presents a set of extensions to the Network Protocol Description Language (NetPDL) allowing support of traffic classification from data-link to application-layer protocols. A set of preliminary experimental results obtained with these new extensions is presented as well.

In this paper, we analyze the use of UML as a starting point to go from design issues to end of production testing of complex embedded systems. The first point is the analysis of the big gap between system signals and UML messages; then the paper focuses on the additional information necessary to fill such gap; different test types are considered, focusing on the application software test; finally the actuation and observation are both analyzed inside the test environment, with particular care to the black-box requirement for behavioral testing. The emphasis of the work is on the resulting test engine definition, verified on a complex case study of a top-of-the-line automotive application; this application is a modern car console, grouping many controls of car-related devices, such as phone, navigation, radio, CD. The testing of GSM capabilities of such device is studied in particular.

Starting from the idea of a general methodology to transform design specifications into system level functional test patterns for complex embedded systems, we propose a layered architecture as basis of such process. The architecture aims at strongly simplifying the test design, allowing the test engineer to concentrate on the high level parts of the system and wrapping all the complexity of the test environment. The results are then verified on a complex case study of automotive applications.

In this paper, we propose the use of a UML methodology to go from user requirements and specifications to end of production testing of complex embedded systems. We consider behavioral, structural and physical levels building a comprehensive and modular model. The process contains the definition of a set of properties being created and then updated in each phase, and heavily relies on message passing and elaborating facilities to increase both abstraction and descriptive power. Result of the process is test pattern generation using custom ATE commands. We also present and discuss an underdevelopment case study of a significantly complex automotive application.