Applications of non-linear time series models on finance and macroeconomics

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Local Hall effect in hybrid ferromagnetic/semiconductor devices

We have investigated the magnetoresistance of ferromagnet-semiconductor devices in an InAs two-dimensional electron gas system in which the magnetic field has a sinusoidal profile. The magnetoresistance of our device is large. The longitudinal resistance has an additional contribution which is odd in applied magnetic field. It becomes even negative at low temperature where the transport is ballistic. Based on the numerical analysis, we confirmed that our data can be explained in terms of the local Hall effect due to the profile of negative and positive field regions. This device may be useful for future spintronic applications.Comment: 4 pages with 4 fugures. Accepted for publication in Applied Physics Letter

Leaching kinetics of copper from waste printed circuit boards by electro-generated chlorine in HCl solution

The leaching behavior of metals such as copper, zinc, lead and tin from waste printed circuit boards (PCBs) has been investigated using electro-generated chlorine in hydrochloric acid solution. The experiments were carried out by employing two different reactors: (a) a combined reactor facilitated with simultaneous Cl2 generation and metal leaching, and (b) a separate metal leaching reactor connected with the anode compartment of a Cl2 gas generator. Leaching efficiency in two reactors was compared for recycling of valuable metals from the PCBs. It was observed that the leaching rate of the metals increased with increase in current density, temperature and time in both reactors. The copper leaching rate gradually diminished when its dissolution was around 20 and 25% in the combined and separate reactor, respectively, which may be attributed to a decrease in surface area of copper with leaching time and the formation of CuCl(s) on the surface. The leaching efficiency of copper was found to be lower in the combined reactor than that of the separate reactor. The dissolution kinetics of copper with electro-generated chlorine followed empirical logarithmic law controlled by surface layer diffusion. The leaching mechanism of copper was further corroborated by SEM-EDS study of the residue. The activation energy for copper leaching in the combined and separate reactors was calculated to be 24.5 and 20.7 kJ/mol, respectively in the temperature range 298–323 K

An Empirical Examination of IT-Enabled Emergency Response: The Cases of Hurricane Katrina and Hurricane Rita

This paper reports the results of an empirical study that analyzes emergency incident response. The paper studies how information systems (IS) complement other organizational assets to help emergency responders achieve satisfactory response performance. We test the research model using empirical data collected from responses to Hurricane Katrina and Hurricane Rita. The results show that IS-enabled asset allocation support directly improves emergency response performance and also positively interacts with non-IS response assets in achieving response success. The results also confirm the value of dispatch systems, interagency communications, and knowledge repositories in developing asset allocation support for an emergency response organization

A Novel Process for Extracting Precious Metals from Spent Mobile Phone PCBs and Automobile Catalysts

A novel process to simultaneously extract the precious metals such as gold, silver, platinum, palladium and rhodium from spent mobile phone printed circuit boards (PCBs) and honeycomb-type auto catalysts by smelting using waste-copper slag without adding any collector metals or by-products such as dross, matte and slime has been developed. In the process, waste-copper slag which is an industrial waste discharged from copper smelter is used not only as a flux for controlling slag composition, but also as a collector metal for capturing precious metals, and a plastic component contained in spent mobile phone PCBs is done as a reducing agent of iron oxides contained in the waste-copper slag. Using the developed process, up to 95% of gold, silver, platinum, palladium and rhodium contained in the raw materials were extracted in a CuFeSn alloy phase, respectively

Piezoelectric Impedance-Based Structural Health Monitoring using Bistable and Adaptive Piezoelectric Circuitry

Structural health monitoring (SHM) has been extensively explored for various aerospace, civil, and mechanical systems due to its significant importance in enhancing life-safety and economic benefits. Among various SHM approaches, the piezoelectric impedance-based method has shown excellent potential in identifying small-sized structural defects, while maintaining simplicity in implementation. This method utilizes high-frequency interrogation to detect small damages based on the electromechanical coupling effect of piezoelectric transducers. This coupling effect enables self-sensing, i.e., the transducer serves as sensor and actuator simultaneously, which facilitates simple implementation with reduced number of transducers and associated electrical wirings while consuming relatively low electric power. Furthermore, the damage characteristics such as the location and severity can be identified by employing baseline models. Despite the promising potentials, important limitations exist to achieve reliable SHM implementations. For example, the number of available independent impedance data set is generally far smaller than the number of required system parameters. As a result, the inverse problems for damage identification are often underdetermined, which severely undermines the reliability of damage prediction since the inverse solutions become extremely sensitive to even small measurement errors, especially in practical implementations where the response anomaly induced by small-sized damages may be easily suppressed by damping and buried in signal noise. To address the limitations and advance the state of the art, this thesis presents a novel methodology that fundamentally improves the underdetermined inverse problem and accurately measures the damage-induced impedance variations to reliably identify small damages under noise influences. This is achieved by strategically integrating bistable and adaptive piezoelectric circuitry with the monitored structure. First, adaptive piezoelectric circuitry with tunable inductor is integrated with the monitored structure, which introduces additional degrees of freedom into the system. By systematically tuning the inductance values, the dynamic characteristics of the electromechanically coupled system can be altered; thereby significantly increased number of different independent impedance variations can be obtained with respect to same damage profile. The enriched data set is then utilized to fundamentally improve the underdetermined inverse problem for damage identification. Next, new bifurcation-based sensing approaches are developed, capitalizing on the strongly nonlinear bifurcation in bistable electrical circuits that exhibit dramatic changes in the response due to small input variations. By utilizing the voltage measured from the piezoelectric transducer as an input to the bistable circuit, the enriched damage-induced piezoelectric impedance changes can be assessed by tracking the circuitry bifurcation points. Considering the stochastic and non-stationary influences on the bifurcation points that are theoretically explored in this thesis, a novel bifurcation-based sensing methodology is developed to provide accurate and robust measurements of the damage-induced impedance changes against unavoidable noise influences. Lastly, the impedance enrichment technique utilizing adaptive piezoelectric circuitry and the advanced bifurcation-based sensing approaches employing bistable circuits are integrated to significantly enhance the reliability of piezoelectric impedance-based damage identification. The important scholarly contributions of this thesis include: (a) newly developed impedance-based SHM method that fundamentally improves the underdetermined inverse problem, (b) novel integration of the monitored structure with bistable circuits for bifurcation-based sensing, and (c) fundamental understanding of the stochastic and non-stationary influences on the saddle-node bifurcation in non-smooth dynamical systems. The bifurcation-based sensing and identification approaches not only enhances the impedance-based SHM, but has the potential of providing high impact to a broad range of sensing and identification systems that are exposed to noise problem.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/140883/1/jinkikim_1.pd

Socio-Cultural Asset Integration for a Green Infrastructure Network Plan in Yesan County, Korea

Green Infrastructure (GI) can be used as a framework for planning human settlements and guiding development away from natural areas that possess high ecological value and provide important Ecosystem Services for society’s development. In this paper, we present a GI Plan for Yesan County (Yesan GI Plan), a small shrinking city in the Republic of Korea. Yesan possesses very rich, but still fairly unexplored natural and cultural resources. Therefore, Yesan’s GI Plan was developed through a multifunctional approach based on the different ecological and socio-cultural characteristics of the region, allowing to connect the core elements that conform the vernacular landscape and get the most out of the Ecosystem Services provided by resources in the area. The plan was defined mainly in two stages: first, applying weights to the different ecological and socio/cultural characteristics; secondly, arranging them through a set of GIS spatial analysis tools using a patch-corridor- matrix model approach. The final outcome is a lean network of ecological value hubs, connected to a set of socio-cultural value assets through a network of water bodies, intrinsic forestry characteristics and wildlife mobility in the area. This was followed in order to connect, facilitate and improve mobility and energy flow in Yesan

PKMiner: a database for exploring type II polyketide synthases

Abstract Background Bacterial aromatic polyketides are a pharmacologically important group of natural products synthesized by type II polyketide synthases (type II PKSs) in actinobacteria. Isolation of novel aromatic polyketides from microbial sources is currently impeded because of the lack of knowledge about prolific taxa for polyketide synthesis and the difficulties in finding and optimizing target microorganisms. Comprehensive analysis of type II PKSs and the prediction of possible polyketide chemotypes in various actinobacterial genomes will thus enable the discovery or synthesis of novel polyketides in the most plausible microorganisms. Description We performed a comprehensive computational analysis of type II PKSs and their gene clusters in actinobacterial genomes. By identifying type II PKS subclasses from the sequence analysis of 280 known type II PKSs, we developed highly accurate domain classifiers for these subclasses and derived prediction rules for aromatic polyketide chemotypes generated by different combinations of type II PKS domains. Using 319 available actinobacterial genomes, we predicted 231 type II PKSs from 40 PKS gene clusters in 25 actinobacterial genomes, and polyketide chemotypes corresponding to 22 novel PKS gene clusters in 16 genomes. These results showed that the microorganisms capable of producing aromatic polyketides are specifically distributed within a certain suborder of Actinomycetales such as Catenulisporineae, Frankineae, Micrococcineae, Micromonosporineae, Pseudonocardineae, Streptomycineae, and Streptosporangineae. Conclusions We could identify the novel candidates of type II PKS gene clusters and their polyketide chemotypes in actinobacterial genomes by comprehensive analysis of type II PKSs and prediction of aromatic polyketides. The genome analysis results indicated that the specific suborders in actinomycetes could be used as prolific taxa for polyketide synthesis. The chemotype-prediction rules with the suggested type II PKS modules derived using this resource can be used further for microbial engineering to produce various aromatic polyketides. All these resources, together with the results of the analysis, are organized into an easy-to-use database PKMiner, which is accessible at the following URL: http://pks.kaist.ac.kr/pkminer. We believe that this web-based tool would be useful for research in the discovery of novel bacterial aromatic polyketides.</p