Real-time Optimal Resource Allocation for Embedded UAV Communication Systems

We consider device-to-device (D2D) wireless information and power transfer systems using an unmanned aerial vehicle (UAV) as a relay-assisted node. As the energy capacity and flight time of UAVs is limited, a significant issue in deploying UAV is to manage energy consumption in real-time application, which is proportional to the UAV transmit power. To tackle this important issue, we develop a real-time resource allocation algorithm for maximizing the energy efficiency by jointly optimizing the energy-harvesting time and power control for the considered (D2D) communication embedded with UAV. We demonstrate the effectiveness of the proposed algorithms as running time for solving them can be conducted in milliseconds.Comment: 11 pages, 5 figures, 1 table. This paper is accepted for publication on IEEE Wireless Communications Letter

The Current Adoption of Dry-Direct Seeding Rice (DDSR) in Thailand and Lessons Learned for Mekong River Delta of Vietnam

The paper documents the joint study trip, organized by CCAFS Southeast Asia for Vietnamese rice researchers, extension workers, as well as local decision makers, to visit Thailand in April 2018. The goal of the study trip was to observe and learn the experience of Thai farmers on the large-scale adoption process of dry-direct seeding rice (DDSR), a viable alternative to address regional scarcity of fresh water in irrigation caused by the drought and salinity intrusion in the Mekong River Delta

Identification of rock mass properties in elasto-plasticity

A simple and effective back analysis method has been proposed on the basis of a new criterion of identification, the minimization of error on the virtual work principle. This method works for both linear elastic and nonlinear elasto-plastic problems. The elasto-plastic rock mass properties for different criteria of plasticity can be well identified based on field measurements

Electronic materials based on conducting metallopolymers and self-assembly

Conducting metallopolymers (CMPs) have been extensively studied due to their potential for various applications in sensing, catalysis, light-emitting diodes, and energy harvesting and storage. The incorporation of metal centers into conjugated organic polymer backbones not only makes these materials multi-functional, but also changes the properties, such as electroactivity and conductivity. In this work, we aim to take advantage of the direct electronic interaction between metal centers and polymer backbones in these metallopolymers to make novel materials that could be used for photovoltaic and spintronic applications. Furthermore, a fundamental study on the interactive role of transition metals in conducting metallopolymers has been conducted, which could help to provide insights for the rational design of metallopolymers for certain applications. Charge transfer in hybrid photovoltaics is often inhibited by the capping ligands on inorganic semiconductors. To bypass the ligand effect, my study was focused on preparing a conducting metallopolymer, in which metal ions are directly bound to the conjugated organic backbone. These metal ions will serve as nucleation or seed points upon which the inorganic semiconductor can grow directly within the polymer matrix. This fabrication method provides materials with direct bonds between the inorganic semiconductor and the conducting polymer backbone and therefore results in direct electronic communication between the donor and acceptor. With this material, the charge transfer limited by capping ligands could be overcome and can result in highly efficient devices when utilized in solar cells. Besides the efforts to harvest energy form renewable resources, changing the way that we use energy (e.g., in lighting and information storage) could also help to reduce our energy demand. The bistability offered by spin-crossover (SCO) complexes has resulted in sustained research interest due to potential applications in molecular electronics such as memory storage. Interested in making memory devices with a bottom up approach, we have designed and prepared CMPs that are not only conductive but also possess spin-crossover behavior. The novelty of this study lies in the fact that spin-switching could be possibly obtained by changing the oxidation states of metal centers, which could be done at room temperature, offering a new method for spin switching compared to conventional methods for SCO such as in thermal-induced spin transition. To study the charge delocalization and charge transport in CMPs, a series of conducting polymers of Schiff-base ligands and metal complexes have been prepared and characterized. Our successful syntheses of ligand polymers allows for full characterization and direct comparison of these polymers to the corresponding metal-containing polymers, from which the role of the metal centers is elucidated. The effects of conjugation length on electrochemical and spectroscopic properties are also investigated and discussed.Chemistr