Trajectory Planning for UAVs equipped with RISs to Provide Aerial LoS Service for Mobile Nodes in 5G/Optical Wireless Communication Networks

Modern wireless communication systems are limited to line-of-sight (LoS) links due to high path loss and blockage issues in millimeter wave (5G) and beyond in optical/visible light communication networks. This letter proposes utilizing (optical) reconfigurable intelligent surface (RIS)-equipped UAV (RISeUAV) to support indirect aerial LoS (ALoS) links for mobile vehicles that deliver critical metropolitan emergency/security services. The RISeUAV performs as an aerial transponder and reflects optical and wireless communication signals in dense urban areas. The navigation problem of the RISeUAV is nontrivial where RISeUAV should be autonomously navigated through an energy-efficient obstacle-free path. Notably, the flight altitude should be relatively low to ensure the quality of ALoS service while the maximum possible ALoS links for vehicles are provided in an obstructed environment. However, designing the flight path for rendering valid ALoS service is an NP-hard problem that is not feasible in real-time for autonomous navigation. We model the RISeUAV navigation as an optimization problem and propose an efficient technique to make the problem computationally tractable in real-time using Benders’ decomposition method and sequential convex programming. Simulation results validate the effectiveness of the proposed method

Intelligent and Robust Control Strategy for Improving Microgrids Operation and Stability

University of Technology Sydney. Faculty of Engineering and Information Technology.The rising world-wide trend toward developing clean and efficient energy resources has caused dispersed installation of distributed generation (DG) units in power systems. Microgrid (MG) concept is considered as the best solution to address the resiliency issue of future modern power systems, which are expected to receive a considerable amount of power through inverter-interfaced DG (IIDG) units. Droop control systems are widely adopted in conventional power systems and the decentralized droop-like control method is the most favorable control system for MGs. However, there are some crucial issues related to the poor performance of droop control in autonomous networked MGs (NMGs), which are considered and addressed in this thesis. The requirement of expensive and unreliable high band-width communication infrastructure is obviated in droop control. To this end, the power network is regarded as a communication link and voltage variables as control signals. This, however, reduces the stability margin of autonomous NMGs due to the interaction of droop controllers through the power network. Lack of inertia of droop-controlled power converters and low X/R ratio of interconnecting power lines intensify this interaction which may lead to the instability of NMGs. On the other hand, the existing parallel-based small-signal model of MGs is inadequate to represent this interaction in the content of NMGs. To this end, an accurate state-space model is developed in a fully decentralized approach for autonomous NMGs which does not rely on any converter for any specific role. Moreover, the major challenges related to NMG control is the ineffectiveness of droop control in accurate power-sharing, frequency fluctuations, and voltage deviation, which raise stability and power quality issues. This work also deals with frequency fluctuation and stability concerns of f-P droop control loop as well as dynamic performance, voltage regulation and stability concerns of V-Q control loop in autonomous NMGs. Besides, penetration of IIDG units puts the stability of modern power systems into risk due to the vague and arbitrary output impedance of IIDG units. In this regard, an optimal voltage regulator (OVR) is proposed for controlling IIDG units to achieve a free/wide range of impedance shaping. The OVR facilitates the optimal impedance shaping based on the control requirement and grid impedance characteristics, which makes the IIDG units consistent with the power network, thus contributing to stabilizing modern power systems and autonomous NMGs. Numerical and simulation results in MATLAB\Simulink platforms are executed to evaluate the effectiveness and accuracy of the proposed methods

A Deep Reinforcement Learning-based Intelligent Grid-Forming Inverter for Inertia Synthesis by Impedance Emulation

In this letter, impedance emulation is exploited for synthesizing inertia in autonomous microgrids. An intelligent grid-forming inverter (GFI) is proposed that facilitates sufficient degrees of freedom for adaptive impedance shaping. The latter adaptively changes the effective bandwidth of the inverter's voltage controller, in response to disturbances for inertia synthesis. Deep reinforcement learning is utilized to tackle the lack of explicit quantitative relation between impedance shaping and inertia. Simulation results prove the effectiveness of the method

Electron Diffraction

Electron microscopes are usually supplied with equipment for obtaining diffraction patterns and micrographs from the same area of a specimen and the best results are attained if the complete use is to be made of these combined facilities. Electron diffraction patterns are used to obtain quantitative data including phase identification, orientation relationship and crystal defects in materials, etc. At first, a general introduction including a geometrical and quantitative approach to electron diffraction from a crystalline specimen, the reciprocal lattice and electron diffraction in the electron microscope are presented. The scattering process by an individual atom as well as a crystal, the Bragg law, Laue conditions and structure factor are also discussed. Types of diffraction patterns such as ring pattern, spot pattern and Kikuchi pattern, and general and unique indexing diffraction patterns are explained. The procedure for indexing simple, complicated and imperfect patterns as well as Kikuchi lines and a combination of Kikuchi lines and spots is outlined. The known and unknown materials are identified by indexing patterns. Practical comparisons between various methods of analysing diffraction patterns are also described. The basic diffraction patterns and the fine structure in the patterns including specimen tilting experiments, orientation relationship determination, phase identification, twinning, second phases, crystallographic information, dislocation, preferred orientation and texture, extra spots and streaks are described in detail. Finally, electron diffraction patterns of new materials are investigated

Brain delivery of valproic acid via intranasal administration of nanostructured lipid carriers: in vivo pharmacodynamic studies using rat electroshock model

The treatment of brain disorders is one of the greatest challenges in drug delivery because of a variety of main barriers in effective drug transport and maintaining therapeutic concentrations in the brain for a prolonged period. The objective of this study was delivery of valproic acid (VPA) to the brain by intranasal route. For this purpose, nanostructured lipid carriers (NLCs) were prepared by solvent diffusion method followed by ultrasonication and characterized for size, zeta potential, drug-loading percentage, and release. Six groups of rats each containing six animals received drug-loaded NLCs intraperitoneally (IP) or intranasally. Brain responses were then examined by using maximal electroshock (MES). The hind limb tonic extension:flexion inhibition ratio was measured at 15-, 30-, 60-, 90-, and 120-minute intervals. The drug concentration was also measured in plasma and brain at the most protective point using gas chromatography method. The particle size of NLCs was 154 ± 16 nm with drug-loading percentage of 47% ± 0.8% and drug release of 75% ± 1.9% after 21 days. In vivo results showed that there was a significant difference between protective effects of NLCs of VPA and control group 15, 30, 60, and 90 minutes after treatment via intranasal route (P < 0.05). Similar protective effect was observed in rats treated with NLCs of VPA in intranasal route and positive control in IP route (P > 0.05). Results of drug determination in brain and plasma showed that brain:plasma concentration ratio was much higher after intranasal administration of NLCs of VPA than the positive control group (IP route). In conclusion, intranasal administration of NLCs of VPA provided a better protection against MES seizure

Transmission Electron Microscopy of Nanomaterials

Structural and analytical characterization, in the nanometer scale, has become very important for all types of materials in recent years. Transmission electron microscope (TEM) is a perfect instrument for this purpose, which is summarized in this chapter. Parameters such as particle size, grain size, lattice type, morphological information, crystallographic details, chemical composition, phase-type, and distribution can be obtained by transmission electron micrographs. Electron diffraction patterns of nanomaterials are also used to acquire quantitative information containing size, phase identification, orientation relationship and crystal defects in the lattice structure, etc. In this chapter, typical electron diffraction, high-resolution transmission and scanning transmission electron microscope imaging in materials research, especially in the study of nanoscience are presented

The effectiveness of worry exposure in treating generalized anxiety disorder

Worry exposure (WE) is a core of cognitive-behavioral treatment for generalized anxiety disorder (GAD). The present study was carried out to examine the efficacy of WE in treating patients with GAD. Three patients with GAD were selected using Structured Clinical Interview for DSM-IV (SCID) based on disorders axis I. Subjects were selected using purposeful sampling, and underwent the treatment after gaining treatment needs. Multiple baseline experimental single case study was used as the method of the present study. The treatment program was carried out for 8 weekly sessions, with a follow up period of 3 months later treatment ending. Subjects completed Pennsylvania State Worry Questionnaire (PSWQ) and Cognitive Avoidance Questionnaire (CAQ). Research findings represented that WE decreased the intensity of GAD symptoms: Pathologic worry and cognitive avoidance. WE has suitable efficacy in treating Generalized Anxiety Disorder and it maintains suitable efficacy in treating GAD