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Open Access Publications from the University of California

Scholarly Works (886 results)

  • Thesis
  • Peer Reviewed
UC Irvine Electronic Theses and Dissertations (2023)

The Internet of Things (IoT) has revolutionized the world, finding widespread utilization across diverse fields, industries, healthcare, and city management. Despite its success, the exponential growth of the IoT market has presented challenges for traditional IoT systems that demand attention. In urban scenarios, the significant influx of data from media-rich sensors poses a strain on local networks with limited resources, impacting their efficiency and effectiveness. Additionally, the impracticality and high cost of deploying sensors and network infrastructures in remote areas creates obstacles to IoT deployment.This thesis aims to explore the utilization of mobile entities as a solution to address these challenges. Specifically, we emphasize the usage of planned entities with predictable or controllable movements to enhance the sensing and networking capabilities of IoT systems, particularly in time-sensitive community IoT applications. Time-sensitive scenarios demand data collection and analysis within specific time frames to preserve data value. To comprehensively investigate the usage of mobility, this thesis explores strategies for integrating mobile entities in diverse scenarios across urban and remote areas, each presenting unique time-sensitivity requirements and design challenges.

In the first scenario, we investigate the utilization of public transit fleets in network-constrained smart city applications. Our proposal involves using these fleets and network infrastructures along their routes to establish a cost-effective backbone network for long-range sensor data transmission, effectively addressing the limitations of local network resources.To achieve this, we develop approaches for optimal deployment of network infrastructure along with planning data collection from public transit fleets, considering the heterogeneity of delay tolerance and priority of sensor data, as well as the trade-off between data delivery delay/loss and network infrastructure installation cost. This thesis evaluates the proposed approaches using real-world bus networks in Orange County, CA and compares them with several other methods.

As a second use case, we investigate the use of drones to enhance sensing coverage in mission-critical IoT applications, specifically high-rise fire monitoring, where in-situ sensors are unavailable due to extreme conditions. We design and implement a drone-based IoT platform for real-time data collection in fire settings. The platform provides a dashboard for firefighters to visualize monitoring areas, user interfaces for commanding tasks to drones, and automatic flight planning for multiple drones to fulfill specified monitoring tasks. We propose multiple-drone flight planning approaches, optimizing data collection processes while considering the heterogeneity of monitoring tasks in terms of periods and priorities, as well as the trade-off between sensing coverage and data quality. The proposed algorithms are evaluated in a simulated high-rise fire scenario with real building structures at UCI. Additionally, we assess the applicability of the proposed system by implementing it in a lab-based testbed with mockup high-rise fires.

In the third scenario, we focus on utilizing drones to assist mobile sensing and sensor data transmission of IoT-based monitoring systems in remote areas with limited in-situ sensors and poor network conditions, particularly for wildland fire monitoring. We automate the drone-based monitoring system by enabling real-time perception of the physical world based on sensor data, automatic task generation for mobile entities, and dynamic planning and control of their movements to continuously monitor dynamic environments. We propose a rule-based task generation procedure for spatial-temporal monitoring requirements based on fire status and prediction. Additionally, we investigate approaches for multiple-drone flight planning, considering data collection timeliness, the trade-off between sensing coverage and data quality, and network disconnection during flights. The proposed flight planning algorithms are evaluated using simulated wildland fire burns at the Blodgett Forest Research Station, and the system's applicability is assessed through lab-based testbed implementation.

Overall, this thesis offers valuable insights into using mobile entities to address challenges in traditional IoT systems and enhance time-sensitive IoT applications. The exploration of different scenarios, from leveraging public transit fleets as a cost-effective backbone network to employing drones for high-rise fire monitoring and remote area sensing, demonstrates the versatility and practicality of mobile solutions in advancing IoT technologies.

    Cover page: Leveraging Mobility to Enhance IoT Applications
    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2014)
    The large increase in upper-ocean sampling during the past decade enables improved estimation of the mean meridional volume transport in the midlatitude South Pacific, and hence of the climatically important Meridional Overturning Circulation. Transport is computed using Argo float profile data for geostrophic shear and trajectory data for reference velocities at 1000 m. For the period 2004-2012, the mean geostrophic transport across 32S is 20.6 ± 6.0 Sv in the top 2000 m of the ocean. From west to east, this includes the southward East Australian Current (23.3 ± 2.9 Sv), its northward recirculation (16.3 ± 3.6 Sv), the broad interior northward flow (18.4 ± 4.1 Sv), and the net northward flow (9.2 ± 2.2 Sv) in opposing currents in the eastern Pacific. The basin-integrated geostrophic transport includes 7.3 ± 0.9 Sv of surface and thermocline waters, 4.9 ± 1.0 Sv of Subantarctic Mode Water, and 4.9 ± 1.4 Sv of Antarctic Intermediate Water. Interannual variability in volume transport across 32S in the South Pacific shows a Southern Annual Mode signature characterized by an increase during the positive phase of the Southern Annular Mode and a decrease during the negative phase. Maximum amplitudes in geostrophic transport anomalies, seen in the East Australian Current and East Australian Current recirculation, are consistent with wind stress curl anomalies near the western boundary. Key Points Improved meridional volume transport in the South Pacific using Argo EAC transport variability tied to the SAM © Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
      Cover page: Meridional volume transport in the South Pacific: Mean and SAM‐related variability
      • Article
      • Peer Reviewed
      UCLA Previously Published Works (2016)

      Background

      Children with intellectual disability (ID) are at heightened risk for developing other psychological disorders, including internalising disorders. Anxiety and depression have been shown to be familial, and parenting is a contributing factor to the development of these disorders. To extend this research, we examined the extent to which mother and father depression and negative, unsupportive parenting related to child internalising behaviour problems, in children with ID or with typical development (TD).

      Method

      Participants were 156 mother and father dyads and their children, assessed at ages 4 and 5 years. We examined parent (mother and father) and child delay status (ID and TD) in relation to measures of both observed and self-reported unsupportive, negative parenting. Utilising moderation models, we examined the relationship between parental depression, unsupportive/negative parenting and child internalising behaviour problems.

      Results

      Unsupportive, negative parenting differed based on parent gender and child delay status. In addition, father depression was a significant moderator of the relationship between unsupportive parenting and child internalising behaviour problems.

      Conclusions

      Children with ID were found to be at higher risk of experiencing unsupportive, negative parenting than children with TD. Children of depressed fathers were especially vulnerable to developing internalising behaviour problems in an unsupportive parenting context.
        Cover page: Unsupportive parenting and internalising behaviour problems in children with or without intellectual disability
        • Article
        • Peer Reviewed
        UC San Diego Previously Published Works (2017)
        Abstract: Observations of absolute velocity based on Argo float profiles and trajectories in the ocean interior show evidence for an equatorward current, the East Pacific Rise current, between 42°S and 30°S, along the western flank of the East Pacific Rise. The East Pacific Rise current carries predominantly intermediate water masses, including Subantarctic Mode Water and Antarctic Intermediate Water, and deeper waters, from the southern edge of the subtropical gyre toward the Equator. The 2004 to 2014 mean East Pacific Rise current transport extrapolated through the 0–2600 m depth range is 8.1 ± 1.6 sverdrup (Sv) (1 Sv = 106 m3 s−1), consistent with a wind‐driven interior transport influenced by the East Pacific Rise topography. While deep ocean mixing and geothermal heating can both create pressure gradients that support geostrophic flows in the deep ocean, this study indicates that about half of the East Pacific Rise current transport is associated with topographic steering of the deep flow over the East Pacific Rise.
          Cover page: The East Pacific Rise current: Topographic enhancement of the interior flow in the South Pacific Ocean
          • Article
          • Peer Reviewed
          UC Riverside Previously Published Works (2018)
          Despite the significant potential of organic piezoelectric materials in the electro-mechanical or mechano-electrical applications that require light and flexible material properties, the intrinsically low piezoelectric performance as compared to traditional inorganic materials has limited their full utilization. In this study, we demonstrate that dimensional reduction of poly(vinylidene fluoride trifluoroethylene) (P(VDF-TrFE)) at the nanoscale by electrospinning, combined with an appropriate thermal treatment, induces a transformative enhancement in piezoelectric performance. Specifically, the piezoelectric coefficient (d33) reached up to -108 pm V-1, approaching that of inorganic counterparts. Electrospun mats composed of thermo-treated 30 nm nanofibers with a thickness of 15 μm produced a consistent peak-to-peak voltage of 38.5 V and a power output of 74.1 μW at a strain of 0.26% while sustaining energy production over 10k repeated actuations. The exceptional piezoelectric performance was realized by the enhancement of piezoelectric dipole alignment and the materialization of flexoelectricity, both from the synergistic effects of dimensional reduction and thermal treatment. Our findings suggest that dimensionally controlled and thermally treated electrospun P(VDF-TrFE) nanofibers provide an opportunity to exploit their flexibility and durability for mechanically challenging applications while matching the piezoelectric performance of brittle, inorganic piezoelectric materials.
            Cover page: Transformative piezoelectric enhancement of P(VDF-TrFE) synergistically driven by nanoscale dimensional reduction and thermal treatment
            • Article
            • Peer Reviewed
            UCLA Previously Published Works (2014)
            © 2014 Elsevier Ltd. Amyotrophic lateral sclerosis has been linked to the gain of aberrant function of superoxide dismutase, Cu,Zn-SOD1 upon protein misfolding. The mechanism of SOD1 misfolding is thought to involve mutations leading to the loss of Zn, followed by protein unfolding and aggregation. We show that the removal of Zn from SOD1 may not lead to an immediate unfolding but immediately deactivates the enzyme through a combination of subtle structural and electronic effects. Using quantum mechanics/discrete molecular dynamics, we showed that both Zn-less wild-type (WT)-SOD1 and its D124N mutant that does not bind Zn have at least metastable folded states. In those states, the reduction potential of Cu increases, leading to the presence of detectable amounts of Cu(I) instead of Cu(II) in the active site, as confirmed experimentally. The Cu(I) protein cannot participate in the catalytic Cu(I)-Cu(II) cycle. However, even without the full reduction to Cu(I), the Cu site in the Zn-less variants of SOD1 is shown to be catalytically incompetent: unable to bind superoxide in a way comparable to the WT-SOD1. The changes are more radical and different in the D124N Zn-less mutant than in the Zn-less WT-SOD1, suggesting D124N being perhaps not the most adequate model for Zn-less SOD1. Overall, Zn in SOD1 appears to be influencing the Cu site directly by adjusting its reduction potential and geometry. Thus, the role of Zn in SOD1 is not just structural, as was previously thought; it is a vital part of the catalytic machinery.
              Cover page: Cu,Zn-Superoxide Dismutase without Zn Is Folded but Catalytically Inactive
              • Article
              • Peer Reviewed
              UC San Francisco Previously Published Works (1984)
              Plasma membranes derived from NR-6 cells, a variant line of Swiss mouse 3T3 cells that does not have cell surface receptors for epidermal growth factor (EGF), inhibited EGF-induced stimulation of DNA synthesis by 50% in serum-starved, subconfluent 3T3 cells. Membranes derived from SV3T3 cells were much less effective in inhibiting EGF-induced DNA synthesis. This inhibition on DNA synthesis by NR-6 membranes was not a direct effect of membranes on EGF, nor could it be overcome by high concentrations of EGF. NR-6 membranes were most effective when added 3 h before EGF addition and had little effect when added 2 h or more after EGF. NR-6 membranes also reduced the stimulation of DNA synthesis induced by platelet-derived growth factor or fibroblast growth factor in serum-starved 3T3 cells. These findings indicate that membrane-membrane interactions between nontransformed cells may diminish their ability to proliferate in response to serum polypeptide growth factors.
                Cover page: Purified plasma membranes inhibit polypeptide growth factor-induced DNA synthesis in subconfluent 3T3 cells.
                • Article
                • Peer Reviewed
                UCLA Previously Published Works (2014)
                Amyotrophic lateral sclerosis has been linked to the gain of aberrant function of superoxide dismutase, Cu,Zn-SOD1 upon protein misfolding. The mechanism of SOD1 misfolding is thought to involve mutations leading to the loss of Zn, followed by protein unfolding and aggregation. We show that the removal of Zn from SOD1 may not lead to an immediate unfolding but immediately deactivates the enzyme through a combination of subtle structural and electronic effects. Using quantum mechanics/discrete molecular dynamics, we showed that both Zn-less wild-type (WT)-SOD1 and its D124N mutant that does not bind Zn have at least metastable folded states. In those states, the reduction potential of Cu increases, leading to the presence of detectable amounts of Cu(I) instead of Cu(II) in the active site, as confirmed experimentally. The Cu(I) protein cannot participate in the catalytic Cu(I)-Cu(II) cycle. However, even without the full reduction to Cu(I), the Cu site in the Zn-less variants of SOD1 is shown to be catalytically incompetent: unable to bind superoxide in a way comparable to the WT-SOD1. The changes are more radical and different in the D124N Zn-less mutant than in the Zn-less WT-SOD1, suggesting D124N being perhaps not the most adequate model for Zn-less SOD1. Overall, Zn in SOD1 appears to be influencing the Cu site directly by adjusting its reduction potential and geometry. Thus, the role of Zn in SOD1 is not just structural, as was previously thought; it is a vital part of the catalytic machinery.
                  • Article
                  • Peer Reviewed
                  UC San Diego Previously Published Works (2016)

                  Background

                  Researchers have primarily relied on mother report to understand the parenting contexts of rearing children with intellectual disabilities. Fathers are increasingly being considered as equally important reporters of their child's behaviours, as they have unique and independent relationships with their children. The purpose of this study was to understand how one source of stress - reports of child behaviour problems - along with spousal support related to parenting tasks, associated with fathers' reports of psychological symptoms over time.

                  Method

                  One hundred eighty-two father participants completed measures of child behaviour problems, spousal support and psychological symptoms. Growth curve modelling was employed to examine paternal psychological symptoms over the child's developmental trajectory.

                  Results

                  Fathers' reports of child behaviour problems predicted initial levels of paternal psychological symptoms but did not predict change in paternal psychological symptoms over time. Spousal support further reduced initial levels of paternal psychological symptoms.

                  Conclusions

                  Child behaviour problems are more important than disability status in predicting father's psychological symptoms. Spousal support predicts paternal psychological symptoms and can be viewed as an additional resource for fathers. Implications for research and practice are discussed.
                    Cover page: Fathers of children with or without ID: understanding long‐term psychological symptoms
                    • Article
                    • Peer Reviewed
                    UC San Diego Previously Published Works (2018)
                    Abstract: Western boundary currents (WBCs) are highly variable narrow meandering jets, making assessment of their volume transports a complex task. The required high-resolution temporal and spatial measurements are available only at a limited number of sites. In this study a method is developed for improving estimates of the East Australian Current (EAC) mean transport and its low-frequency variability, using complementary modern datasets. The present calculation is a case study that will be extended to other subtropical WBCs. The method developed in this work will reduce uncertainties in estimates of the WBC volume transport and in the interannual mass and heat budgets of the meridional overturning circulations, improving our understanding of the response of WBCs to local and remote forcing on long time scales. High-resolution expendable bathythermograph (HR-XBT) profiles collected along a transect crossing the EAC system near Brisbane, Australia, are merged with coexisting profiles and parking-depth trajectories from Argo floats, and with altimetric sea surface height data. Using HR-XBT/Argo/altimetry data combined with Argo trajectory-based velocities at 1000 m, the 2004–15 mean poleward alongshore transport of the EAC is 19.5 ± 2.0 Sv (1 Sv ≡ 106 m3 s−1) of which 2.5 ± 0.5 Sv recirculate equatorward just offshore of the EAC. These transport estimates are consistent in their mean and variability with concurrent and nearly collocated moored observations at 27°S, and with earlier moored observations along 30°S. Geostrophic transport anomalies in the EAC system, including the EAC recirculation, show a standard deviation of ±3.1 Sv at interannual time scales between 2004 and 2015.
                      Cover page: Estimating the velocity and transport of Western Boundary Current systems: A case study of the East Australian Current near Brisbane
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