Multi-hop wireless ad hoc wireless networks have no fixed network infrastructure. Such a network consists of multiple nodes that maintain network connectivity through wireless links. Additionally, these nodes may be mobile and thus the topology of the network may change with time. It will be useful if the nodes in this network could communicate with the Internet; this can be done via gateways which in turn interconnect to the Internet. This functionality requires that the nodes in the ad hoc network to discover the gateway, using a gateway discovery protocol. However, a limiting factor (particularly for mobile nodes) is suing their limited energy supply provided by batteries. In order to understand the potential effect this thesis considers two key areas: internetworking between a multi-hop mobile wireless ad hoc network and the Internet and the energy utilization as a function of number of gateways and the mobility pattern of nodes. Using simulation on various mobility patterns and networks density scenarios, we show that increase the number of gateways in ad hoc network significantly improves the power efficiency of mobile node and therefore prevent network partition due to death nodes. The thesis also discusses about the impact of different environment and mobility patterns on the power consumption of mobile nodes which is a very important factor in the building and deployment of the cost-effective high performance wireless ad hoc networks.

The frequent occurrences of natural and technological disasters have incurred grave loss of life and damage to property. For mitigating the miserable aftermaths, multi-robot teleoperation systems have been developed and deployed to cooperate with human rescuers in post-earthquake scenarios, and to sample, monitor and clean pollutants in marine environments. With a bidirectional communication channel, human users can deliver commands/requests to guide the motions of the remote robots, and can receive visual/audio feedback to supervise the status of the remote environment, throughout multi-robot teleoperation. Furthermore, the remote robots can send force feedback to human operators to improve their situational awareness and task performance. This way, a closed-loop multi-robot teleoperation system becomes bilateral in which coordinated robots physically interact and exchange energy with human users, and hence needs to be rendered passive for safe human-robot interaction. Beyond guaranteeing closed-loop passivity, the control of a bilateral multi-robot teleoperation system faces two challenging problems: preserving the communication connectivity of the remote robots; and dispatching the teleoperation authority to multiple human users. Because wireless transmission of radio/acoustic signals between the remote robots is constrained by their distances, bilateral multi-robot teleoperation control must coordinate the motions of the remote robots appropriately so as to maintain their communication network connected. Further, multiple human users can send possibly conflicting teleoperation commands to the remote robots, a distributed authority dispatch algorithm is thus needed for the remote robot network to recognize and follow the most urgent user commands at runtime. This thesis develops an energy shaping strategy to preserve the connectivity of the remote robots, and to dispatch control authority over the remote robots to human users, during bilateral multi-robot teleoperation. Chapter 1 introduces the application background of multi-robot teleoperation as well as the state-of-the-art development in related research areas. In Chapter 2, a dynamic interconnection and damping strategy is proposed to reduce and constrain the position error between the local and remote robots to any prescribed bound during bilateral teleoperation. Chapter 3 derives a gradient plus damping control from a bounded potential function and then unifies it into an indirect coupling framework to preserve all communication links of an autonomous multi-robot system with time-varying delays and bounded actuation. On these bases, Chapter 4 develops a dynamic feedforward-feedback passivation strategy to preserve all communication links and thus the connectivity of the tree network of the remote robots while rendering the bilateral multi-robot teleoperation close loop passive. Specifically, by blending the sliding variable in Chapter 2 with the bounded potential function in Chapter 3, the dynamic passivation strategy decomposes the dynamics of the remote robots into a power-preserving interconnection of two subsystems, and regulates the energy behaviour of each subsystem to preserve the tree communication connectivity of the remote robots. To handle time-varying communication delays, the strategy further transforms the communication channels between the local and remote robots into a dynamic controller for passivating bilateral teleoperation. Superior to existing controls, the strategy using a bounded potential function can circumvent numerical instability, reduce noise sensitivity and facilitate future extensions to accommodate robot actuator saturation. On the other side, Chapter 5 designs a distributed and exponentially convergent winners-take-all authority dispatch algorithm that activates the teleoperation of only human users with the most urgent requests in real time. After formulating the problem as a constrained quadratic program, we employ an exact penalty function method to construct a distributed primal-dual dynamical system that can solve the problem at an exponential rate. Because the equilibrium of the system changes with user requests, we then interconnect the dynamical system with physical robot dynamics in a power-preserving way, and passivate closed-loop multi-robot teleoperation using multiple storage functions from a switched system perspective. Finally, Chapter 6 provides some conclusive remarks and two problems regarding connectivity preservation and authority dispatch for future study. / Graduate

Background: Recently there has been a revitalization in research on classic psychedelic substances. This class of drugs has been found to produce intense and profoundly meaningful experiences, and offers a unique opportunity to study the neural correlates of the sense of self. The objective of this research was to systematically review the effects of classic psychedelics on spontaneous brain activity, as measured on three electrophysiological modalities: spectral analysis, signal diversity, and functional connectivity. Method: We searched Pubmed to identify papers in English, published between January 1990 to May 2021, where electrophysiological methods were used to evaluate the effects of classic psychedelics in healthy individuals during non-task resting states. Results: Sixteen papers were included. Classic psychedelic substances generally decrease spectral power in most frequency bands, mainly in the alpha range, increase signal diversity, and decrease the flow of information throughout the brain. Conclusion: Decreases in alpha power, increased signal diversity, and decreases in default mode network activity might be important neural correlates of the psychedelic state. However, inconsistencies in the results and heterogeneity in study design are some of the limitations that have to be considered when interpreting these results.

Social anxiety disorder (SAD) interferes with everyday life. It can, for instance, hinder careers, relationships, and leisure time. It is a common anxiety disorder that was neglected for decades. SAD individuals crave and fear social interactions simultaneously, leading to isolation in our highly social world. Therefore, research surrounding these kinds of disorders is essential. This systematic review has focused on the neural aspects and differences between SAD and healthy controls surrounding amygdala activation and connectivity. Functional magnetic resonance imaging (fMRI) studies conducted using social and emotional tasks were included. Findings include increased amygdala activation to fearful faces and words and a positive correlation between amygdala activation and symptom severity. Further, deficits in emotion regulation and a finding of gradual habituation have been found in SAD compared to healthy controls. Some limitations to this research are the small sample sizes used in the included articles and the use of both SAD and individuals with generalized SAD. The study is essential to assess future questions and directions regarding diagnosis, treatment, and understanding of SAD.

QUIC is a relatively new transport layer network protocol that has gained popularity over the last few years. The protocol was initially developed by Google and standardization work has been continued by the Internet Engineering Task Force (IETF) with the goal of it becoming the next generation transport protocol. While the standardization work is not yet finished, the protocol has seen a large adoption, already covering a large portion of the internet traffic. As a new protocol, many researchers have studied QUIC and compared it to TCP in typical scenarios. However, few studies have been performed on QUIC in specific scenarios. In this thesis, we present the first performance study of QUIC over Dual Connectivity (DC). DC is a multi-connectivity technique that allows users to connect to multiple cell towers with one user equipment. It is an important lower-layer feature accelerating the transition from 4G to 5G, which is also expected to play an important role in standalone 5G networks. With DC, higher throughput and reliability can be achieved by using multiple paths simultaneously. However, the drawback of DC is that it introduces packet reordering and jitter, which can significantly impact the performance of upper-layer protocols such as TCP and QUIC. To study the extent of this effect, a testbed is set up to evaluate QUIC over DC. Our performance evaluation compares the throughput of QUIC over DC with that of TCP over DC, and evaluates the fairness of QUIC over DC. Using a series of throughput and fairness experiments, we show how QUIC is affected by different DC parameters, network conditions, and whether the DC implementation aims to improve throughput or reliability. Our findings provide network operators with insights into understanding the impacts of splitting QUIC traffic in a DC environment. We show the value of increasing the UDP receive buffers when running QUIC over DC and that QUIC can utilize the increased bandwidth and reliability in DC, provided that the links' characteristics are similar. We also show that with reasonably selected DC parameters and increased UDP receive buffers, QUIC over DC performs similarly to TCP over DC and achieves optimal systemwide fairness under symmetric link conditions when DC is not used for packet duplication.

Vehicle to Vehicle (V2V) communication provides a flexible and real-time information dissemination mechanism through various applications of Intelligent Transportation Systems (ITS). Achieving seamless connectivity through multi-hop vehicular communication with sparse network is a challenging issue. In this paper, we have studied this multi-hop vehicular connectivity in an urban scenario using GPS traces obtained from San Francisco Yellow cabs. Our current work describes a new algorithm for the analysis of topological properties like connectivity and partitions for any kind of vehicular or mobile computing environment. The novel approach uses bitwise manipulation of sparse matrix with an efficient storage technique for determining multi-hop connectivity. The computation mechanism can be further scaled to parallel processing environment. The main contribution of this research is threefold. First, developing an efficient algorithm to quantify multi-hop connectivity with the aid of bitwise manipulation of sparse matrix. Second, investigating the time varying nature of multi-hop vehicular connectivity and dynamic network partitioning of the topology. Third, deriving a mathematical model for calculating message propagation rate in an urban environment.

The ability to attentively filter sensory information and manipulate it in working memory is critical for our ability to interact with the world. Although primary and secondary sensory cortical areas have been well-studied, frontal lobe contributions to sensory attention and working memory remain under-investigated. This dissertation investigates the topography and network organization of sensory-biased and multi-sensory regions in the healthy human brain using functional magnetic resonance imaging (fMRI). First, this research developed a series of functional connectivity analyses of data from the Human Connectome Project to validate and extend recently localized auditory-biased network structures, transverse gyrus intersecting the precentral sulcus (tgPCS) and caudal inferior frontal sulcus (cIFS), and visual-biased network structures, superior precentral sulcus (sPCS) and inferior precentral sulcus (iPCS), in lateral frontal cortex (LFC). Results replicated the original findings and extended them by revealing five additional bilateral LFC regions, including middle inferior frontal sulcus (midIFS) and frontal operculum (FO), differentially connected to either the visual- or auditory-biased networks. Due to inter-subject anatomical variability, identification of sPCS, tgPCS, iPCS and cIFS depends critically on within-subject analyses. Next, this work demonstrated that an individual’s unique pattern of resting-state functional connectivity can accurately identify their specific pattern of working memory (WM) and attention task activation in LFC using “connectome fingerprinting” (CF). CF predictions were superior to group-average predictions and matched the accuracy of within-subject task-based functional localization. This research developed and validated methods that use intrinsic functional connectivity information to perform functional brain analyses on highly idiosyncratic brain regions. Finally, a combined auditory, tactile and visual WM study revealed the joint organization of sensory-biased and multi-sensory regions within individual subjects. Hypothesized visual-biased midIFS and auditory-biased FO regions were functionally confirmed for the first time. Several bilateral tactile-biased regions, premotor dorsal, premotor ventral, anterior middle frontal gyrus, middle insula, postcentral sulcus, posterior middle temporal gyrus and pre-supplemental motor area, abutting previously described visual- and auditory-biased regions were identified. Several multi-sensory WM regions, recruited in each stimulus modality, were observed to partially overlap with visual-biased regions. Intrinsic functional connectivity analyses revealed that regions segregate into networks largely based upon their modality preferences. / 2020-06-14T00:00:00Z

The field of marine population connectivity is receiving growing attention from ecologists worldwide. The degree to which metapopulations are connected via larval dispersal has vital ramifications for demographic and evolutionary dynamics and largely determines the way we manage threatened coastal ecosystems. Here we addressed different questions relating to connectivity by integrating direct and indirect genetic approaches over different spatial and ecological scales in a coral reef fish in the Red Sea. We developed 35 novel microsatellite loci for our study organism the two-band anemonefish Amphiprion bicinctus (Rüppel 1830), which served as the basis of the following approaches. First, we collected nearly one thousand samples of A. bicinctus from 19 locations across 1500 km along the Saudi Arabian coast to infer population genetic structure. Genetic variability along the northern and central coast was weak, but showed a significant break at approximately 20°N. Implementing a model of isolation by environment with chlorophyll-a concentrations and geographic distance as predictors we were able to explain over 90% of the genetic variability in the data (R2 = 0.92). For the second approach we sampled 311 (c. 99%) putative parents and 172 juveniles at an isolated reef, Quita al Girsh (QG), to estimate self-recruitment using genetic parentage analysis. Additionally we collected 176 juveniles at surrounding locations to estimate larval dispersal from QG and ran a biophysical dispersal model of the system with real5 time climatological forcing. In concordance with model predictions, we found a complete lack (c. 0.5%) of self-recruitment over two sampling periods within our study system, thus presenting the first empirical evidence for a largely open reef fish population. Lastly, to conceptualize different hypotheses regarding the underlying processes and mechanisms of self-recruitment versus long-distance dispersal in marine organisms with pelagic larval stages, I introduce and discuss the concept of “origin effects”, providing the theoretical background to some of the questions that have arisen during this research. Overall, this thesis has generated significant new insights into the patterns of coral reef fish connectivity, specifically for the Red Sea, where such information has previously been scarce.

Broad-scale population genetics can reveal population structure across an organism’s entire range, which can enable us to determine the most efficient population-wide management strategy depending on levels of connectivity. Genetic variation and differences in genetic diversity on small-scales have been reported in anemones, but nothing is known about their broad-scale population structure, including that of “host” anemone species, which are increasingly being targeted in the aquarium trade. In this study, microsatellite markers were used as a tool to determine the population structure of a sessile, host anemone species, Heteractis magnifica, across the Indo-Pacific region. In addition, two rDNA markers were used to identify Symbiodinium from the samples, and phylogenetic analyses were used to measure diversity and geographic distribution of Symbiodinium across the region. Significant population structure was identified in H. magnifica across the Indo-Pacific, with at least three genetic breaks, possibly the result of factors such as geographic distance, geographic isolation and environmental variation. Symbiodinium associations were also affected by environmental variation and supported the geographic isolation of some regions. These results suggests that management of H. magnifica must be implemented on a local scale, due to the lack of connectivity between clusters. This study also provides further evidence for the combined effects of geographic distance and environmental distance in explaining genetic variance.

A thesis submitted to the Faculty of Science and Agriculture in fulfilment of the Degree of Doctor of Philosophy in the Department of Computer Science at the University of Zululand, 2017 / InfrastructureWireless Mesh Networks (I-WMNs) are increasingly used to provide network connectivity and Internet access to previously under-served areas in the developing world. It is common for some of these deployments to be battery-powered due to a lack of electrical infrastructure in the targeted areas. Thus, the energy-efficiency of these networks gains additional importance. Topology Control (TC) has been previously reported to improve the energy-efficiency and network performance of wireless ad-hoc networks, including I-WMNs. However,simulation-based studies have been relied upon to reach these conclusions and the study of TC prototypes applicable to I-WMNs has largely been limited to design issues. Thus, the study of the efficacy of TC prototypes as a mechanism for improving energy-fficiency and network performance remains an open issue. The thesis addresses this knowledge gap by studying the dynamic, run-time behaviours and the network topologies created by two standards-compatible TC prototypes. This study provides unique insight into how the prototypes consume computational resources, maintain network connectivity, produce cumulative transceiver power savings and affect the workings of the routing protocol being employed. This study also documents the topology instability caused by transceiver power oscillations produced by the PlainTC prototype. A context-based solution to reduce transceiver power oscillations and the subsequent topology instability is proposed. This solution applies the Principal Component Analysis statistical method to historical network data in order to derive the weights associated with each of the identified context variables. A threshold value is defined that only permits a node to adjust its transceiver power output if the observed change in a node’s context exceeds the threshold. The threshold mechanism is incorporated into the PlainTC+ prototype and is shown to reduce topology instability whilst improving network performance when compared to PlainTC.The results obtained in this study suggest that I-WMN topologies formed by TC are able to closely match the performance of networks that do not employ TC. However, this study shows that TC negatively affects the energy efficiency of the network despite achieving cumulative transceiver power savings.