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  • [ November 11, 2019]

    Lipid metabolism in the green microalga Chlamydomonas reinhardtii

    | Microalgae are fast-growing microorganisms that have developed efficient mechanisms to harvest and transform solar energy into energy-rich molecules such as lipids. They are thus potentially great renewable cell factories for production of fuels and biomaterials for the chemical industries. However, several biological as well as engineering challenges need to be addressed before the establishment of a profitable algal industrial biotechnology. The main goal of Li-Beisson’s laboratory is to investigate the molecular mechanisms involved in the conversion of solar energy and atmospheric CO2 to energy-dense compounds such as oil and hydrocarbon. The molecular limitations of these mechanisms are assessed and novel strategies are proposed for synthetic biology of microalgae. The further use of this knowledge will aid in the design and creation of strains for algal biotechnology. In this communication, she will present current projects and highlight major findings from her group.
  • [ November 11, 2019]

    Distributed Filtering for Cyber-Physical Systems: Consistency, Stability and Security

    | In this talk, the distributed filtering problem over cyber-physical systems (CPS) is investigated. First, a scalable and fully distributed Kalman filter is provided and analyzed to achieve the consistent estimation for the states of potentially unstable systems. Then, we study the case with state equality constraints (SEC). We propose a distributed Kalman filter with guaranteed consistency and satisfied SEC Then, we establish the relationship between consensus step, SEC and estimation error covariance in dynamic and steady processes, respectively. Under an extended collective observability condition based on SEC, the stability of the filter is studied. Moreover, we consider a secure distributed filtering problem for linear time-invariant systems with bounded noises and unstable dynamics under compromised observations. We first propose a recursive distributed filter consisting of saturation-like observation update and consensus operation of state estimates. A sufficient condition is then established for the boundedness of estimation error.
  • [ November 11, 2019]

    Bio-Inspired Autonomy for Mobile Sensor Networks in Aquatic Environment

    | There is a perceivable trend for robots to serve as networked mobile sensing platforms that are able to collect data in aquatic environment in unprecedented ways. The need for undisturbed operation of search and monitoring posts higher goals for sustainable autonomy. This talk reviews recent developments in autonomous collective foraging in aquatic environment that explicitly integrates insights from biology with models and provable strategies from control theory and robotics. One of the interesting insights is that sensing is used to enable implicit communications among agents, which is able to achieve coordinated behaviors while incorporating individual differences. The algorithms are rigorously analyzed and modified for mobile robots. Experimental effort with promising results demonstrates that bio-inspired autonomy might be preferred in aquatic environment that features severe limitation in communication.
  • [ October 28, 2019]

    Atomristors: Memory Effect and Applications in 2D Materials

    | This talk will present the latest research progress on the atomic-level details of non-volatile resistance switching (NVRS) in 2D memory devices In particular, we will focus on memory characteristics and atomistic imaging and transport studies, together with the first principle calculations on the common point defects of 2D materials. For this investigation, we employ the STM to characterize the vertical metal-insulator-metal (MIM) memory device and examine the defect sites in atomic resolution to elucidate memory phenomenon. These studies provide one to one correlation between the structural and electronic properties of the heterogeneities and their role in the resistance switching mechanism. Applications from RF switches to neuromorphic computing will be highlighted.
  • [ October 28, 2019]

    Metal halide perovskites for optoelectronics: the interplay of physics and chemistry

    | Metal halide perovskites have attracted enormous attention in the scientific community in recent years. This attention has been drawn by breakthroughs in perovskite optoelectronics, mainly in photovoltaics and LEDs Although there has been great progress in their use in optoelectronics, fundamentally understanding this class of materials is still challenging, in particular the interplay of several physical and chemical processes. Many fundamental questions are left unanswered, such as what makes them unique/excellent semiconductors; how to tune their optoelectronic properties; why some compositions are more stable than others; the consequence of their chemical instability on their optoelectronic properties; and how to stabilize them. We, the Computational Materials Physics Group, focus on addressing such questions using computer simulations and theoretical analyses based on the laws of Quantum Mechanics. In this talk, I will highlight our recent progress and give an outlook of our next challenges with a discussion of future strategy along this line of research.
  • [ October 25, 2019]

    High-Fidelity Simulation of Premixed Flames

    | Lean premixed combustion is the desired combustion regime in industrial gas turbines. It results in a low level of NOX due to operating at lower temperatures and facilitates better combustion efficiency. However, the primary issue with operating gas turbines in this regime is thermoacoustic instability, commonly initiated by combustion-generated sound. To avoid this type of instability, the mechanism of sound generation by premixed flames needs to be fully understood. This presentation will provide a technical review of our understanding of the mechanism of sound generation by premixed flames. Examples from direct numerical simulation (DNS) studies undertaken at the University of Melbourne are provided. Furthermore, the implications of the findings for developing accurate models that can predict combustion-generated sound are discussed.
  • [ October 10, 2019]

    Nanostructured Electrocatalysts for Energy-relevant Conversion Processes

    | Replacement of precious metal catalysts by commercially available alternatives is of great importance among both fundamental and practical catalysis research. Nanostructured carbon-based and transition metal materials have demonstrated promising catalytic properties in a wide range of energy generation/storage applications. Specifically engineering carbon with guest metals/metal-free atoms can improve its catalytic activity for electrochemical oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), thus can be considered as potential substitutes for the expensive Pt/C or IrO2 catalysts in metal-air batteries and water splitting process. In this presentation, I will talk about the synthesis of nonprecious metal and metal free elements-doped graphene, and their application on electrocatalysis [1-6]. The excellent OER and HER performance (high catalytic activity and efficiency) and reliable stability indicate that new materials are promising highly efficient electrocatalysts for clean energy conversion. I will also present some research results of electrocatalytic CO2 reduction eraction (CRR) and N2 reduction reaction (NRR) conducted in my research group [7-10].
  • [ October 10, 2019]

    Metal Halide Perovskite Solar Cell Research by Surface Science and Advanced Characterization

    | Metal halide perovskite materials and devices have become one of the most active research fields and continues to progress rapidly on various fronts. My group at OIST is making efforts to use surface science and advanced material characterization to obtain in-depth understanding about perovskite materials and devices. Instability, upscalability and lead toxicity are currently the major challenges for perovskite photovoltaic technology to move forward towards commercialization. In this talk, I will present our research progress on degradation mechanisms of perovskite materials], development of strategies to improve perovskite solar cell device stability, reduction of lead leakage using self-healing polymer-based encapsulation, upscalable fabrication of perovskite solar cells and modules, and surface science understanding of perovskite materials and stability.
  • [ October 09, 2019]

    Rare-Event Simulation of Regenerative Systems

    | Rare events occur by definition with a very small probability but are important to analyze because of potential catastrophic consequences. During this talk, we will focus on rare event for so-called regenerative processes, that are basically processes such that portions of the process are statistically independent of each other. For many complex and/or large models, simulation is the only tool at hand but requires specific implementations to get an accurate answer in a reasonable time. There are two main families of rare-event simulation techniques: importance sampling (IS) and splitting.

    This talk is mostly based on collaborative works with Peter W. Glynn and Marvin K. Nakayama.
  • [ September 26, 2019]

    Decision-Environment Co-evolutionary Game Dynamics in A Closed Loop

    | In response to the growing interest in how to efficiently influence complex systems of interacting self-interested agents, new efforts have been made to address open problems related to the analysis and control of evolutionary matrix games, with particular emphasis on applications in social, economic, biological and robotic networks. In our evolutionary game models for networks of interacting agents, we consider both the decision-making dynamics of interacting multiple populations and the evolution of the environment affecting the game payoffs. It is then possible to perform global convergence analysis for the resulting closed-loop co-evolutionary dynamics, to identify in particular under what conditions the dynamics converge to periodic orbits The goal is to build a general framework towards optimal control of evolutionary games on networks and ultimately resolving social dilemmas in large populations of interacting self-interested agents.
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