Freezing of an unconventional two-dimensional plasma

We study an unconventional two-dimensional, two-component classical plasma on a sphere, with emphasis on detecting signatures of melting transitions. This system is relevant to Ising-type quantum Hall states, and is unconventional in the sense that it features particles interacting via two different two-dimensional Coulomb interactions. One species of particles in the plasma carries charge of both types (Q_1,Q_2), while the other species carries only charge of the second type (0,-Q_2). We find signatures of a freezing transition at Q_1^2 approximately 140. This means that the species with charge of both types will form a Wigner crystal, whereas the species with charge of the second type also shows signatures of being a Wigner crystal, due to the attractive inter-component interaction of the second type. Moreover, there is also a Berezinskii-Kosterlitz-Thouless phase transition at Q_2^2 approximately 4, at which the two species of particles bind to form molecules that are neutral with respect to the second Coulomb interaction. These two transitions appear to be independent of each other, giving a rectangular phase diagram. As a special case, Q_2=0 describes the (conventional) two-dimensional one-component plasma. Our study is consistent with previous studies of this plasma, and sheds new light on the freezing transition of this system.Comment: 8 pages, 8 figures. Submitted to Physical Review

April 22, 2014

The Breeze is the student newspaper of James Madison University in Harrisonburg, Virginia

Columbia Chronicle (05/01/2000)

Student newspaper from May 1, 2000 entitled Columbia Chronicle. This issue is 28 pages and is listed as Volume 33, Number 24. Cover story: Columbia adopts new grading policy Managing Editor: Valerie Dannerhttps://digitalcommons.colum.edu/cadc_chronicle/1480/thumbnail.jp

Doctor of Philosophy

dissertationCommunication surpasses computation as the power and performance bottleneck in forthcoming exascale processors. Scaling has made transistors cheap, but on-chip wires have grown more expensive, both in terms of latency as well as energy. Therefore, the need for low energy, high performance interconnects is highly pronounced, especially for long distance communication. In this work, we examine two aspects of the global signaling problem. The first part of the thesis focuses on a high bandwidth asynchronous signaling protocol for long distance communication. Asynchrony among intellectual property (IP) cores on a chip has become necessary in a System on Chip (SoC) environment. Traditional asynchronous handshaking protocol suffers from loss of throughput due to the added latency of sending the acknowledge signal back to the sender. We demonstrate a method that supports end-to-end communication across links with arbitrarily large latency, without limiting the bandwidth, so long as line variation can be reliably controlled. We also evaluate the energy and latency improvements as a result of the design choices made available by this protocol. The use of transmission lines as a physical interconnect medium shows promise for deep submicron technologies. In our evaluations, we notice a lower energy footprint, as well as vastly reduced wire latency for transmission line interconnects. We approach this problem from two sides. Using field solvers, we investigate the physical design choices to determine the optimal way to implement these lines for a given back-end-of-line (BEOL) stack. We also approach the problem from a system designer's viewpoint, looking at ways to optimize the lines for different performance targets. This work analyzes the advantages and pitfalls of implementing asynchronous channel protocols for communication over long distances. Finally, the innovations resulting from this work are applied to a network-on-chip design example and the resulting power-performance benefits are reported

Redox-electrolytes for non-flow electrochemical energy storage: A critical review and best practice

Over recent decades, a new type of electric energy storage system has emerged with the principle that the electric charge can be stored not only at the interface between the electrode and the electrolyte but also in the bulk electrolyte by redox activities of the electrolyte itself. Those redox electrolytes are promising for non-flow hybrid energy storage systems, or redox electrolyte-aided hybrid energy storage (REHES) systems; particularly, when they are combined with highly porous carbon electrodes. In this review paper, critical design considerations for the REHES systems are discussed as well as the effective electrochemical characterization techniques. Appropriate evaluation of the electrochemical performance is discussed thoroughly, including advanced analytical techniques for the determination of the electrochemical stability of the redox electrolytes and self-discharge rate. Additionally, critical summary tables for the recent progress on REHES systems are provided. Furthermore, the unique synergistic combination of porous carbon materials and redox electrolytes is introduced in terms of the diffusion, adsorption, and electrochemical kinetics modulating energy storage in REHES systems. © 2018 The Author(s

ACTIVIST ORGANIZATIONS AND STRATEGIC UTILIZATION OF INFORMATION AND COMMUNICATION TECHNOLOGIES: AN EXPLORATION OF CODEPINK: WOMEN FOR PEACE

Ph.D.Ph.D. Thesis. University of Hawaiʻi at Mānoa 201

Redox electrolytes for non-flow electrochemical energy storage

In recent decades, a new type of electric energy storage system has emerged with the principle that the electric charge can be stored not only at the interface between the electrode and the electrolyte, but also in the electrolyte by the redox activities of the bulk electrolyte itself. Such redox electrolytes are promising for non-flow energy storage (redox electrolyte aided hybrid energy storage systems, REHES) particularly when they are combined with electrodes made of nanoporous carbon. In this PhD work, I have established a fundamental understanding regarding ion diffusion, process kinetics, and adsorption of redox ions. For that, different REHES systems have been investigated including tetrapropylammonium iodide, zinc iodide, potassium iodide, potassium ferricyanide, vanadyl sulfate, tin sulfate, and tin fluoride. The basic understanding of REHES systems enabled the targeted improvement of the device performance throughout this PhD work. Compared to the energy storage capacity of a conventional (non-redox) electrical double layer capacitor of 4 Wh/kg (ca. 80 F/g), the use of the ZnI2 redox electrolyte yielded significantly higher performance of up to 226 Wh/kg. Furthermore, the specific power was also enhanced from 1.3 kW/kg to 20 kW/kg. As a key conclusion, this PhD work demonstrates the high attractiveness of REHES systems not only from a performance point of view, but also regarding low cost and simplicity of the system.Die Forschung der letzten Jahrzehnte hat eine neue Art der elektrochemischen Energiespeicherung hervorgebracht, bei der elektrische Ladung nicht nur an der Grenzfläche zwischen der Elektrode und dem Elektrolyten gespeichert wird, sondern auch im Elektrolyten selbst durch dessen Redoxaktivität. Diese Redox-Elektrolyte sind für hybride Energiespeichersysteme ohne extern-mechanische Bewegung des Elektrolyten (REHES) vielversprechend, insbesondere, wenn hochporöse Kohlenstoffmaterialien als Elektroden verwendet werden. In dieser Doktorarbeit wurden verschiedene REHES-Systeme hinsichtlich der Diffusion, der elektrochemischen Kinetik und der Adsorption von Redox-Ionen untersucht, um grundlegende Effekte und Prozesse aufzuklären. Die Kombination grundlegender Elektrochemie und Materialcharakterisierung ermöglichte es, die Leistungsparameter von REHES im Vergleich zum Stand der Technik deutlich zu verbessern. Die Energiespeicherkapazität des herkömmlichen wässrigen elektrischen Doppelschichtkondensators ohne Redoxelektrolyt von 4 Wh/kg (entspricht 80 F/g) wurde zum Beispiel im ZnI2 System auf bis zu 226 Wh/kg gesteigert, während die spezifische Leistung von 1.3 kW/kg auf 20 kW/kg verbessert werden konnte. Als Ergebnis zeigt sich, dass REHES ein besonders vielversprechender Ansatz zur Darstellung hochleistungsfähiger elektrochemischer Energiespeicher ist. Weitere Vorteile von REHES sind ein vereinfachtes Zellkonzept und die Verwendung von potentiell kostengünstige Einzelkomponenten

Redox electrolytes for non-flow electrochemical energy storage

In recent decades, a new type of electric energy storage system has emerged with the principle that the electric charge can be stored not only at the interface between the electrode and the electrolyte, but also in the electrolyte by the redox activities of the bulk electrolyte itself. Such redox electrolytes are promising for non-flow energy storage (redox electrolyte aided hybrid energy storage systems, REHES) particularly when they are combined with electrodes made of nanoporous carbon. In this PhD work, I have established a fundamental understanding regarding ion diffusion, process kinetics, and adsorption of redox ions. For that, different REHES systems have been investigated including tetrapropylammonium iodide, zinc iodide, potassium iodide, potassium ferricyanide, vanadyl sulfate, tin sulfate, and tin fluoride. The basic understanding of REHES systems enabled the targeted improvement of the device performance throughout this PhD work. Compared to the energy storage capacity of a conventional (non-redox) electrical double layer capacitor of 4 Wh/kg (ca. 80 F/g), the use of the ZnI2 redox electrolyte yielded significantly higher performance of up to 226 Wh/kg. Furthermore, the specific power was also enhanced from 1.3 kW/kg to 20 kW/kg. As a key conclusion, this PhD work demonstrates the high attractiveness of REHES systems not only from a performance point of view, but also regarding low cost and simplicity of the system.Die Forschung der letzten Jahrzehnte hat eine neue Art der elektrochemischen Energiespeicherung hervorgebracht, bei der elektrische Ladung nicht nur an der Grenzfläche zwischen der Elektrode und dem Elektrolyten gespeichert wird, sondern auch im Elektrolyten selbst durch dessen Redoxaktivität. Diese Redox-Elektrolyte sind für hybride Energiespeichersysteme ohne extern-mechanische Bewegung des Elektrolyten (REHES) vielversprechend, insbesondere, wenn hochporöse Kohlenstoffmaterialien als Elektroden verwendet werden. In dieser Doktorarbeit wurden verschiedene REHES-Systeme hinsichtlich der Diffusion, der elektrochemischen Kinetik und der Adsorption von Redox-Ionen untersucht, um grundlegende Effekte und Prozesse aufzuklären. Die Kombination grundlegender Elektrochemie und Materialcharakterisierung ermöglichte es, die Leistungsparameter von REHES im Vergleich zum Stand der Technik deutlich zu verbessern. Die Energiespeicherkapazität des herkömmlichen wässrigen elektrischen Doppelschichtkondensators ohne Redoxelektrolyt von 4 Wh/kg (entspricht 80 F/g) wurde zum Beispiel im ZnI2 System auf bis zu 226 Wh/kg gesteigert, während die spezifische Leistung von 1.3 kW/kg auf 20 kW/kg verbessert werden konnte. Als Ergebnis zeigt sich, dass REHES ein besonders vielversprechender Ansatz zur Darstellung hochleistungsfähiger elektrochemischer Energiespeicher ist. Weitere Vorteile von REHES sind ein vereinfachtes Zellkonzept und die Verwendung von potentiell kostengünstige Einzelkomponenten