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Delay Tolerant Networking (DTN) has been proposed as a new architecture to provide efficient store-carry-and-forward data transport in satellite networks. Since these networks relay on scheduled contact plans, the Contact Graph Routing (CGR) algorithm can be used to optimize routing and data delivery performance. However, in spite of the various improvements that have been made to CGR, there have been no significant proposals to prioritize traffic with different quality of service requirements. In this work we propose adaptations to CGR that allow performance improvements when sending traffic with different latency constraints, and develop a linear programming optimization model that works as a performance upper bound. The simulation results of the proposed schemes are promising and open the debate on other ways to improve performance while meeting the particular needs of heterogeneous traffic., 6 pages, 2 figures

Recent advances have shown that satellite communication (SatCom) will be an important enabler for next generation terrestrial networks as it can provide numerous advantages, including global coverage, high speed connectivity, reliability, and instant deployment. An ideal alternative for radio frequency (RF) satellites is its free-space optical (FSO) counterpart. FSO or laser SatCom can mitigate the problems occurring in RF SatCom, while providing important advantages, including reduced mass, lower consumption, better throughput, and lower costs. Furthermore, laser SatCom is inherently resistant to jamming, interception, and interference. Owing to these benefits, this paper focuses on downlink laser SatCom, where the best ground station (GS) is selected among numerous candidates to provide reliable connectivity and site diversity. To quantify the performance of the proposed scheme, we derive closed-form outage probability and ergodic capacity expressions for two different practical GS deployment scenarios. Thereafter, asymptotic analysis is conducted to obtain the overall site diversity order, and aperture averaging is studied to illustrate the impact of aperture diameter on the overall performance. Furthermore, we investigate the site diversity order for a constellation of satellites that are communicating with the best GS by using opportunistic scheduling. Finally, important design guidelines that can be useful in the design of practical laser SatComs are outlined.

Garg, Goldwasser and Vasudevan (Eurocrypt 2020) invented the notion of deletion-compliance to formally model the “right to be forgotten’, a concept that confers individuals more control over their digital data. A requirement of deletion-compliance is strong privacy for the deletion requesters since no outside observer must be able to tell if deleted data was ever present in the first place. Naturally, many real world systems where information can flow across users are automatically ruled out. The main thesis of this paper is that deletion-compliance is a standalone notion, distinct from privacy. We present an alternative definition that meaningfully captures deletion-compliance without any privacy implications. This allows broader class of data collectors to demonstrate compliance to deletion requests and to be paired with various notions of privacy. Our new definition has several appealing properties: •It is implied by the stronger definition of Garg et al. under natural conditions, and is equivalent when we add a strong privacy requirement. •It is naturally composable with minimal assumptions. •Its requirements are met by data structure implementations that do not reveal the order of operations, a concept known as history-independence. Along the way, we discuss the many challenges that remain in providing a universal definition of compliance to the “right to be forgotten.”, 18th International Conference on Privacy, Security and Trust (PST 2021), Dec. 13-15, 2021, Auckland, New Zealand [Held Virtually], Series: Annual Conference on Privacy, Security and Trust, PST

Post stroke individuals going through rehabilitation exercises are given feedback on their performances to potentially regain a normal gait. Research suggests that technologically complemented feedback helps patients reinforce behavioral changes faster via neuroplasticity. In this work, we develop a novel wearable real-time auditory feedback and gait analysis system: AudiTread. The device can provide auditory feedback on multiple parameters based on the thresholds set on the computer system and other variables can be added if required through its code accessible online. The device consists on multiple distance sensors, Bluetooth-enabled microcontroller, battery management system - all of which are integrated together to form an easily replicable system. The device is tested against standard Vicon data through time-series data analysis and signal processing to demonstrate the validity of the prototype. A comprehensive testing with stroke patients is currently under way and shall be followed. An elaborate description is provided on how system can be constructed and thereby corroborated.

The impact of moisture diffusion on two types of fully integrated stacks was investigated. One of them with dense SiO 2 layers and the other with ultra low k (ULK), both of which are predominantly used in BEOL (Back End of Line) as inter layer dielectric films. For half of the samples of each dielectric, their surrounding seal ring was intentionally damaged. Storage of these samples was then performed either at ambient or at 85°C/85% relative humidity (RH) for five months to study the impact of moisture. Capacitance measurements and current voltages curves were used to assess moisture effect. For intact seal ring samples, no variations are observed for both dielectrics, which confirms the moisture protection offered by surrounding seal ring. For damaged seal ring structures, there is no variation neither after five months at ambient nor at 85°C/85% RH for dense SiO 2 structures. However, very significant variations are observed on capacitance and breakdown values of ULK structures. The effect of baking on these samples was then investigated. Baking at 125°C or 250°C does not give full recovery of capacitance in the integrated stacks. Moreover, its effect is not permanent. Finally, to assess moisture diffusion path, time of flight — secondary ion mass spectrometry (Tof-SIMS) analysis was performed. Moisture seems to diffuse at ULK/SiCN interfaces.

We proposed a simple noise model based on the photon transfer method for the testing of a hybrid optical sensor for imaging in short-wavelength infrared regime. The proposed testing procedure allowed us to separate the noise sources and then work on noise mitigation., 2019 IEEE Research and Applications of Photonics in Defense Conference, RAPID 2019, August 19-21, 2019, Miramar Beach, FL, USA

Community walking remains compromised in the majority of stroke survivors even after rehabilitation. We developed a virtual reality (VR) toolkit prototype to provide intensive, task-specific training of complex locomotor tasks as required for community walking in safe yet ecological virtual environments. The toolkit, supported by best evidence and developed using low-cost VR tools, comprises of 6 dimensions that include endurance, walking speed, postural transitioning environmental encumbrance, cognitive load and a more complex dimension combining encumbrance and cognitive load. Feedback collected through hands-on interaction and focus groups with stroke participants and clinicians will be used to refine the prototype. The resulting VR toolkit will be combined to field training practice as part of a multi-centered intervention study to enhance community walking in stroke survivors.

Gait asymmetry, one of the hallmarks of post stroke locomotion, often persists despite gait rehabilitation interventions, impacting negatively on functional mobility. This pilot study examines the feasibility and instantaneous effects of real time visual feedback provided in the form of an avatar on gait symmetry. Preliminary results obtained from seven chronic stroke survivors showed no improvements in step length and step time ratios while using three avatar views (back, frontal and paretic side). Improvements in lower limb joint angle symmetry, however, were observed. Faster walking speed and larger paretic step length were also noted during the adaptation and post-adaptation phases. We are currently extending the study to a larger sample to validate the use of real time visual feedback to enhance spatial parameters of gait among stroke survivors.

The paper reviews the robustness/reliability achievements and include previously published data related to the hybrid bonding module for W2W and D2W bonding techniques.

The recent proliferation of drones has contributed to the emergence of new threats in security applications. Because of their great agility and small size, UAS can be used for numerous missions and are very challenging to detect. Radar technology with its all-weather capability can play an important role in detecting UAS-based threats and in protecting critical assets. However, to be successful, radars have to quickly scan large volumes with great sensitivity, eliminate nuisance alarms from birds and discriminate UAS from ground targets. Radar parameters, antenna scan techniques and target classification requirements for UAS detection are analyzed. A radar implementation is discussed and preliminary results presented. Overall, an X-band radar with electronic scanning capability can contribute to a reliable and affordable solution for detecting UAS-based threats.

Background: Accidents and deaths associated to mobile communications while walking are on the rise, while the influence of phone messaging on the ability to avoid moving obstacles remains poorly understood. Objectives: This study aims to describe the extent to which reading messages at different stages of the avoidance strategy affects circumvention of pedestrians. Methods: Healthy adults (n = 5, 36.2 ± 6 years (mean ±1SD)) were tested while walking overground and viewing a virtual subway station in a helmet mounted display. Three virtual avatars were positioned 7m ahead of the participant (±40° right/left and straight ahead (0°)). As participants walked 0.5m, one avatar randomly moved towards a theoretical point of collision located on the midline. Messages, when present, were randomly delivered at 0.5m and 2.5m of participants' forward displacement. Body movements were recorded with a Vicon system. Results: For diagonal obstacle approaches only, a trend towards reduced minimum walking speed was observed in response to reading phone messages as compared to when no messages were displayed. No consistent changes in obstacle minimal clearance or distance at onset of avoidance strategy were observed with the introduction of text messages. Conclusions: Slower minimum walking speeds in the presence of text messages for diagonally approaching obstacles may have facilitated deciphering the text messages while maintaining a safe clearance from the obstacles during the avoidance strategy. For centrally approaching obstacles, however, such reduction in walking speed would have been unhelpful as a change in walking trajectory is mandatory to prevent a collision in that condition.

Locomotor adaptations to circumvent moving obstacles are initiated with respect to obstacle and self-motion perception, in order to predict and avoid an impending collision. We have developed a virtual reality (VR) based obstacle circumvention task to assess locomotor adaptation (experiment [Exp] 1) and the ability to predict an impending collision (Exp 2) as well as detection of the onset of obstacle motion (Exp 3). The locomotor (Exp 1) and seated perceptuomotor [Exp 2–3] behaviors were contrasted between post-stroke (n=12) and healthy participants (n=12). Three red cylindrical obstacles approaching from head-on (0°) and diagonally (30° left/right) were seen in a virtual room along with a blue central target inside a helmet-mounted display. In Exp 1, participants walked towards the target while avoiding collision with the approaching obstacles. The delay in initiation of an avoidance strategy after the initiation of obstacle motion was assessed. In Exp 2, obstacles moved diagonally (left/right) at a fixed speed of 0.75 m/s while the virtual scene moved at 0.5, 0.75 and 1 m/s, thus creating ‘collision’ and ‘no collision’ conditions. Participants were instructed to indicate their prediction of such using the joystick. In Exp 3, participants were instructed to indicate as soon as they perceived motion of obstacle in the virtual scene. The delay in pressing the joystick button after initiation of obstacle motion was assessed. Individuals with stroke initiated locomotor avoidance strategies significantly later than healthy individuals for all obstacle approaches. This delay, however, was not associated with the delay in obstacle detection. No significant difference was found in either the accuracy of collision prediction or the delay in detection of obstacle motion. However, two post-stroke individuals who collided frequently with obstacles demonstrated low accuracy in predicting an impending collision. One of them also showed significant delays in detecting initiation of obstacle motion when compared with others. Thus, the seated perceptuomotor tasks may reveal underlying sensory-perceptual and cognitive deficits post-stroke. VR based locomotor obstacle circumvention along with seated perceptuomotor assessments provide a comprehensive understanding of obstacle circumvention behavior and the underlying perceptual and cognitive factors shaping them in post-stroke and healthy individuals.

Background: Virtual reality (VR) is increasingly being incorporated into research and clinical practice. Its usefulness, however, remains largely dependent on the extent to which it elicits human behaviors that are similar to those observed in the real world. Objectives: In this study, we estimated whether obstacle avoidance strategies while walking in response to pedestrians approaching from different directions differed when performed in a virtual (VE) vs. physical environment (PE). We also examined the extent to which avoidance strategies in the VE change with repeated practice. Methods: Participants (n=4) were assessed while walking overground and avoiding moving pedestrians in both a VE and a PE, in a random order. Three female collaborators acted as interferers in the PE experiment. For the VE experiment, we created avatars using full body kinematics recorded from the actors. The task consisted of walking towards a target while avoiding one of the interferers, which could approach from either the left or right side (±30°), or from the center (0°). In a fourth condition, all interferers walked away (no obstacle). Results: Delayed onset times of avoidance strategy and slower walking speeds were observed in the VE vs. PE. With practice in the VE, there was a progressive decrease in onset time of avoidance strategy and an increase in walking speed. Differences between the two environments, however, persisted by the end of the experiment. Maximal trajectory deviation and distance at onset of avoidance strategy remained comparable between the VE and PE throughout the experiment. Conclusion: Obstacle avoidance behavior in response to moving pedestrians differs in the VE vs. PE, although spatial parameters (e.g. distance at the onset and maximum lateral deviation) appear to be similar. Differences decrease but remain present despite of repeated exposure to the VE. Results should be taken into consideration when using the VR technology for assessment or training purposes.

Background: Avoiding collisions with other pedestrians during overground locomotion is a trivial task for young adults, but with age or for stroke survivors it can become a daunting endeavour. Coordinated eye-head movements probably play an important role in obstacle circumvention, but unfortunately the literature on the subject is rather scarce. Objectives: The aim of this study was therefore to investigate eye-head coordination during overground locomotion, and, more specifically, during avoidance of dynamic virtual pedestrians. Methods: We recorded eye (ASL eyetracker ) and body (Vicon system) movements in five healthy young adults during overground locomotion as they navigated in a virtual environment visualized in a helmet mounted display. Medio-lateral (ML) displacements as well as the pattern of eye, head and gaze reorientation in the horizontal plane were examined. Participants were instructed to walk toward a goal represented by a blue target located 9.5m straight ahead and to avoid a non-reactive human-like avatar coming from different angles of approach. Results: We found that ML trajectory displacements were preceded by a head rotation in the direction of veering. Halfway through the ML head displacement, a head rotation in the direction opposite to that of the ML displacement was observed. Head rotations were themselves preceded by eye saccade(s) toward the side of circumvention. During the circumvention, no attempt was made to keep the head in alignment with the goal. Conclusions: Eye/gaze movements appear to play an important role during the avoidance of dynamic obstacles while walking. Eye movements are initiated ahead of the trajectory ML displacement, possibly to localize the obstacle and/or plan the future walking trajectory.

This paper presents a novel particle swarm optimization (PSO) algorithm that combines the strengths of several PSO variants into a single competitive algorithm. This novel algorithm, named Time Adaptive Dual Particle Swarm Optimization (TAD-PSO), is comprised of two specialized populations, with one focusing on exploration of the search space and the other on exploitation. The main population, specialized in exploration, uses orthogonal learning to create information-rich exemplars which intelligently guide particle movement throughout the search space. The auxiliary population uses a PSO variant known for its very fast convergence speed, and thus very high performance on unimodal problems. This population is specialized in exploitation of the interesting local minima. The main population size decays linearly, to foster exploration early and convergence in the later stages of the optimization procedure. Additionally, TAD-PSO does not have the topological structure of the swarm as an algorithm hyper-parameter, making it a fast and simple algorithm to apply to new problems. TAD-PSO was tested extensively and compared to 6 widely used PSO variants on 19 benchmark problems, for 10, 30 and 100 dimensions. TAD-PSO consistently ranked first in each dimensional space, making it a competitive optimization algorithm on both unimodal and multimodal problems.

Background: Unilateral spatial neglect (USN), a highly prevalent post-stroke impairment, has been strongly associated with poor functional outcomes in self-care and instrumental activities of daily living. Hence, its sensitive detection is crucial. Yet, conventional USN assessments present with significant limitations, often leading to misdiagnosis. Virtual reality (VR) can be used to counteract those issues and increase detection sensitivity. Objective: To examine the feasibility, refine development and promote future implementation of a novel Ecological VR-based Evaluation of Neglect Symptoms (EVENS). Methods: EVENS consists of two (simple and complex) immersive, 3-D scenes, depicting grocery shopping shelves, where object-detection and navigation tasks are performed using a joystick. Through a cross-sectional study, the effects of virtual scene complexity on navigational and detection abilities in patients with (USN+) and without (USN−) post-stroke USN and in healthy controls (HC) were determined. These findings were complimented by gathering the opinion of clinicians and experts in the field as to the barriers/facilitators to the use of VR and the features for an optimal assessment. Results: Longer detection times and larger mediolateral deviations from ideal paths were found in USN+ vs. USN− and HC groups. Several barriers/facilitators for clinical VR use and features of an optimal VR-based tool were identified. Conclusion: Navigation and detection abilities are affected by environmental complexity of the VR scene in individuals with post-stroke USN and can be employed for USN assessment. The present knowledge translation initiatives can refine EVENS' design and promote its future application and adherence to its use in clinical settings.

Gait asymmetry, one of the hallmarks of post-stroke locomotion, often persists despite of gait rehabilitation interventions and negatively affects functional mobility. This pilot study examines the feasibility and instantaneous effects of real-time visual feedback provided in the form of a virtual avatar replicating on gait symmetry after stroke. Based on the results obtained from one chronic stroke survivor, step length and step time ratios were improved towards normal values (1.0) in presence of the avatar displayed in a third person back and paretic side view, while mixed results were observed for the front view condition. Gains were not maintained following the removal of the avatar. These preliminary results, to be confirmed in a larger sample of participants, support the feasibility of using virtual avatars as a source of visual feedback to promote gait symmetry in stroke survivors.