Swinburne University of Technology

About: Swinburne University of Technology is a education organization based out in Melbourne, Victoria, Australia. It is known for research contribution in the topics: Galaxy & Population. The organization has 7223 authors who have published 25530 publications receiving 667955 citations. The organization is also known as: Swinburne Technical College & Swinburne College of Technology.

Topologies and Control Schemes of Bidirectional DC–DC Power Converters: An Overview

Abstract: Bidirectional DC-DC power converters are increasingly employed in diverse applications whereby power flow in both forward and reverse directions are required. These include but not limited to energy storage systems, uninterruptable power supplies, electric vehicles, and renewable energy systems, to name a few. This paper aims to review these converters from the point of view of topology as well as control schemes. From the point of view of topology, these converters are divided into two main categories, namely non-isolated and isolated configurations. Each category is divided into eight groups along with their respective schematics and a table of summary. Furthermore, the common control schemes and switching strategies for these converters are also reviewed. Some of the control schemes are typically applied to all DC-DC power converters such as PID, sliding mode, fuzzy, model predictive, digital control, etc. In this context, it should be noted that some switching strategies were designed specifically for isolated bidirectional DC-DC converters in order to improve their performance such as single phase shift, dual phase shift, triple phase shift, etc. The features of each topology and control scheme along with their typical applications are discussed, in order to provide a ground of comparison for realizing new configurations or finding the appropriate converter for the specific application.

Below melting point photothermal reshaping of single gold nanorods driven by surface diffusion

Abstract: Plasmonic gold nanorod instability and reshaping behavior below melting points are important for many future applications but are yet to be fully understood, with existing nanoparticle melting theories unable to explain the observations. Here, we have systematically studied the photothermal reshaping behavior of gold nanorods irradiated with femtosecond laser pulses to report that the instability is driven by curvature-induced surface diffusion rather than a threshold melting process, and that the stability dramatically decreases with increasing aspect ratio. We successfully utilized the surface diffusion model to explain the observations and found that the activation energy for surface diffusion was dependent on the aspect ratio of the rods, from 0.6 eV for aspect ratio of 5 to 1.5 eV for aspect ratio less than 3. This result indicates that the surface atoms are much easier to diffuse around in larger aspect ratio rods than in shorter rods and can induce reshaping at any given temperature. Current plasmo...

Gas Metallicities in the Extended Disks of NGC?1512 and NGC?3621. Chemical Signatures of Metal Mixing or Enriched Gas Accretion?

Abstract: We have obtained spectra of 135 H II regions located in the inner and extended disks of the spiral galaxies NGC?1512 and NGC?3621, spanning the range of galactocentric distances 0.2-2 ? R 25 (from ~2-3?kpc to ~18-25?kpc). We find that the excitation properties of nebulae in the outer (R > R 25) disks are similar to those of the inner disks, but on average younger H II regions tend to be selected in the bright inner disks. Reddening by dust is not negligible in the outer disks and subject to significant large-scale spatial variations. For both galaxies, the radial abundance gradient flattens to a constant value outside of the isophotal radius. The outer disk O/H abundance ratio is highly homogeneous, with a scatter of only ~0.06?dex. In the case of the interacting galaxy NGC?1512 we find a number of H II regions with peculiar metallicity for their radius, a result which can be interpreted by gas flows activated by the gravitational encounter with NGC?1510. Based on the excitation and chemical (N/O ratio) analysis, we find no compelling evidence for variations in the upper initial mass function of ionizing clusters of extended disks. The O/H abundance in the outer disks of the target galaxies corresponds to ~35% of the solar value (or higher, depending on the metallicity diagnostic). This agrees with our earlier measurements in M83 and NGC?4625, and conflicts with the notion that metallicities in extended disks of spiral galaxies are low and on the order of ~0.1 ? Z ?. We show that, in general, the observed metal enrichment cannot be produced with the current level of star formation, even if the latter extends over a Hubble time. We discuss the possibility that metal transport mechanisms from the inner disks lead to metal pollution of the outer disks. Gas accretion from the intergalactic medium, enriched by outflows, offers an alternative solution, justified within the framework of hydrodynamic simulations of galaxy evolution. Specific model predictions of the chemical enrichment and the flat gradients in extended disks of nearby galaxies will be valuable to discriminate between these different scenarios.

Prescribed Finite-Time Consensus Tracking for Multiagent Systems With Nonholonomic Chained-Form Dynamics

Abstract: This paper deals with the consensus tracking problem for a multiagent system with nonholonomic chained-form dynamics. A new distributed observer is first proposed for each follower to estimate the leader state and the leader input in a prescribed finite-time under both undirected and directed communication graphs. Then based on the observer and by adding a power integrator, a novel nonlinear protocol is designed such that the estimated leader state is tracked in a prescribed finite-time. Different from some existing finite-time consensus tracking approaches, an explicit bound without dependence on initial states is derived for the settling time. Therefore, in an unknown environment where initial conditions are unavailable, the proposed strategy is able to meet specific system requirements, e.g., a military target is tracked by a group of field robots in a prescribed time. Finally, numerical examples are provided to demonstrate the effectiveness of the proposed protocol.

Nonlinear optical endoscopy based on a double-clad photonic crystal fiber and a MEMS mirror.

Abstract: Two-photon fluorescence and second harmonic generation microscopy have enabled functional and morphological in vivo imaging. However, in vivo applications of those techniques to living animals are limited by bulk optics on a bench top. Fortunately, growing functionality of fiber-optic devices and miniaturization of scanning mirrors stimulate the race to develop nonlinear optical endoscopy. In this paper, we report on a prototype of a nonlinear optical endoscope based on a double-clad photonic crystal fiber to improve the detection efficiency and a MEMS mirror to steer the light at the fiber tip. The miniaturized fiber-optic nonlinear microscope is characterized by rat esophagus imaging. Line profiles from the rat tail tendon and esophagus prove the potential of the technology in in vivo applications.