Broadband Power Line Communication in Railway Traction Lines: A Survey

Power line communication (PLC) is a technology that exploits existing electrical transmission and distribution networks as guiding structures for electromagnetic signal propagation. This facilitates low-rate data transmission for signaling and control operations. As the demand in terms of data rate has greatly increased in the last years, the attention paid to broadband PLC (BPLC) has also greatly increased. This concept also extended to railways as broadband traction power line communication (BTPLC), aiming to offer railway operators an alternative data network in areas where other technologies are lacking. However, BTPLC implementation faces challenges due to varying operating scenarios like urban, rural, and galleries. Hence, ensuring coverage and service continuity demands the suitable characterization of the communication channel. In this regard, the scientific literature, which is an indicator of the body of knowledge related to BTPLC systems, is definitely poor if compared to that addressed to BPLC systems installed on the electrical transmission and distribution network. The relative papers dealing with BTPLC systems and focusing on the characterization of the communication channel show some theoretical approaches and, rarely, measurements guidelines and experimental results. In addition, to the best of the author's knowledge, there are no surveys that comprehensively address these aspects. To compensate for this lack of information, a survey of the state of the art concerning BTPLC systems and the measurement methods that assist their installation, assessment, and maintenance is presented. The primary goal is to provide the interested readers with a thorough understanding of the matter and identify the current research gaps, in order to drive future research towards the most significant issues

Wearable Brain-Computer Interfaces based on Steady-State Visually Evoked Potentials and Augmented Reality: a Review

Brain–computer interfaces (BCIs) are an integration of hardware and software communication systems that allow a direct communication path between the human brain and external devices. Among the existing BCI paradigms, steady-state visually evoked potentials (SSVEPs) have gained momentum in the development of noninvasive BCI applications as they are characterized by adequate signal-to-noise ratio (SNR) and information transfer rate (ITR). In recent years, the adoption of augmented reality (AR) head-mounted displays (HMDs) to render the flickering stimuli necessary for SSVEPs elicitation has become an attractive alternative to traditional computer screens (CSs). In fact, the increase in system wearability anticipates the possibility of adopting BCIs in contexts other than research laboratory. This has contributed to a steadily-increasing interest in BCIs, as also confirmed by the recent literature dedicated to the topic. In this evolving scenario, this review intends to provide a comprehensive picture of the current state-of-the-art in relation to the latest advancement of wearable BCIs based on SSVEPs classification and AR technology. The goal is to provide the reader with a systematic comparison of different technological solutions realized over the last years, thus making future research in this direction more efficient

Experimental procedure for metrological characterization of AR-based eye-tracking interfaces

Given the increasing demand for hands-free input interfaces within Augmented Reality (AR) applications, this paper addresses an experimental characterization of eye-tracking technology as an input mechanism for AR Head-Mounted Displays (HMDs). To this end, an AR application was developed with the aim of simulating a real-world application scenario. In this scenario, a set of objects is rendered within the scene so that each object can associated with a distinct command to be executed. The purpose of the developed application is to assess the capability of the input interface in accurately recognizing the objects selected through ocular movements. This evaluation also encompasses the interface performance in detecting the user-declared point of gaze, thereby quantifying the error between the user-reported focus and the interface perceptual outcomes. As a case study, without loss of generalization, the AR HMD Microsoft HoloLens 2 is considered. Eight different subjects were involved in the experimental campaign. The obtained experimental results showcase satisfactory performance with HoloLens 2. This paves the way for more robust development of eye-tracking-based applications, even in scenarios with stringent requirements

Infrared Thermography for Real-Time Assessment of the Effectiveness of Scoliosis Braces

This work proposes an innovative method, based on the use of low-cost infrared thermography (IRT) instrumentation, to assess in real time the effectiveness of scoliosis braces. Establishing the effectiveness of scoliosis braces means deciding whether the pressure exerted by the brace on the patient’s back is adequate for the intended therapeutic purpose. Traditionally, the evaluation of brace effectiveness relies on empirical, qualitative assessments carried out by orthopedists during routine follow-up examinations. Hence, it heavily depends on the expertise of the orthopedists involved. In the state of the art, the only objective methods used to confirm orthopedists’ opinions are based on the evaluation of how scoliosis progresses over time, often exposing people to ionizing radiation. To address these limitations, the method proposed in this work aims to provide a real-time, objective assessment of the effectiveness of scoliosis braces in a non-harmful way. This is achieved by exploiting the thermoelastic effect and correlating temperature changes on the patient’s back with the mechanical pressure exerted by the braces. A system based on this method is implemented and then validated through an experimental study on 21 patients conducted at an accredited orthopedic center. The experimental results demonstrate a classification accuracy slightly below 70% in discriminating between adequate and inadequate pressure, which is an encouraging result for further advancement in view of the clinical use of such systems in orthopedic centers

Performance Measurement of Gesture-Based Human–Machine Interfaces Within eXtended Reality Head-Mounted Displays

This paper proposes a method for measuring the performance of Human–Machine Interfaces based on hand-gesture recognition, implemented within eXtended Reality Head-Mounted Displays. The proposed method leverages a systematic approach, enabling performance measurement in compliance with the Guide to the Expression of Uncertainty in Measurement. As an initial step, a testbed is developed, comprising a series of icons accommodated within the field of view of the eXtended Reality Head-Mounted Display considered. Each icon must be selected through a cue-guided task using the hand gestures under evaluation. Multiple selection cycles involving different individuals are conducted to derive suitable performance metrics. These metrics are derived considering the specific parameters characterizing the hand gestures, as well as the uncertainty contributions arising from intra- and inter-individual variability in the measured quantity values. As a case study, the eXtended Reality Head-Mounted Display Microsoft HoloLens 2 and the finger-tapping gesture were investigated. Without compromising generality, the obtained results show that the proposed method can provide valuable insights into performance trends across individuals and gesture parameters. Moreover, the statistical analyses employed can determine whether increased individual familiarity with the Human–Machine Interface results in faster task completion without a corresponding decrease in accuracy. Overall, the proposed method provides a comprehensive framework for evaluating the compliance of hand-gesture-based Human–Machine Interfaces with target performance specifications related to specific application contexts

A General Framework for Closed Loop Negative Feedback Multivariable Physiological Control Systems: Existence, Uniqueness, and Stability of Homeostatic Equilibrium Points

The study of homeostatic equilibrium is a key concern in several fields, from physiology and biology to medicine and biomedical engineering. Control theory approaches can provide effective strategies to model physiological control systems, helping in understanding the dynamics of bio- and physio-logical regulation processes. However, the intrinsic complexity of living systems makes it difficult to identify unified biomodels that can represent a wide variety of physiological systems. In this context, the present work proposes a general framework to model the dynamics and describe the behavior of a wide class of multivariable physiological control systems, from the molecular to the whole-organ scale. The framework adopts a structure based on a closed-loop topology taking into account multiple inputs and outputs and with the negative feedback action intrinsically embedded within the model. The development of such a general model has at least three important repercussions: the first concerns the possibility of better understanding the basic mechanisms common to many physiological systems; the second is to develop a common theoretical framework to enable effective approaches to the analysis and design of synthetic biological control systems; finally, the investigation of the structural properties of the model in a general context, allows a guided and simplified application to specific cases. To this regard, in this paper, the existence, possible uniqueness and stability properties of the homeostatic equilibrium points of the general model are investigated; the theoretical framework is then illustrated through two real-world case-studies: (i) the PI3K/AKT/mTOR pathway nonlinear dynamics, a critical regulator of cellular growth, proliferation, and survival; (ii) the control mechanism of the neuromuscular stretch reflex, among the prime triggers implicated in postural control. Results proved the capability of the proposed framework to capture the intricate dynamics of multivariable physiological systems at different scales, highlighting the existence of asymptotically stable homeostatic equilibrium and allowing the study of the impact of transmission delays on the system’s stability. At the best of authors’ knowledge, following the paper Ponsiglione et al. (2023) where monovariable systems where dealt with, the proposed methodology is the first attempt to represent and investigate homeostasis from the molecular up to systemic level by exploiting a unified multivariable biomodeling architecture, which makes it a novel approach to understanding homeostatic control from a broader perspective