Self-organized quasiparticles and other patterns in planar gas-discharge systems

A summary is given for the work that has been done on pattern formation in planar ac- and dc- gas-discharge systems with high ohmic and dielectric barrier respectively at the Institute of Applied Physics at the University of Muenster. WeIl defined stationary and moving solitary filaments are observed that may be referred to as selforganized quasiparticles. Among others, filaments can be scattered, generated, or annihilated, and the formation of filament clusters ("molecules") is observed. For appropriate parameters filaments in the "gaseous" phase are observed, and the condensation of large assemblies to "crystalline" phase and "liquid" phase is recorded, too. Filaments may generate superstructures e.g. domain patterns. The experimental work demonstrates that a filament is a generic pattern. In addition, reference is made to non-filamentary patterns. Finally, a list of references referring to models and numerical treatment is presented

Localized patterns in planar gas-discharge systems

A summary is given of parts of the work that has been done on pattern formation in planar ac- and dc- gas-discharge systems with high ohmic and dielectric barrier respectively, at the Institute of Applied Physics of the University of Muenster. In addition, a qualitative reactiondiffusion model is reviewed that takes account of many of the effects that have been observed experimentally

Dielectric-barrier discharges in two-dimensional lattice potentials

We use a pin-grid electrode to introduce a corrugated electrical potential into a planar dielectric-barrier discharge (DBD) system, so that the amplitude of the applied electric field has the profile of a two-dimensional square lattice. The lattice potential provides a template for the spatial distribution of plasma filaments in the system and has pronounced effects on the patterns that can form. The positions at which filaments become localized within the lattice unit cell vary with the width of the discharge gap. The patterns that appear when filaments either overfill or under-fill the lattice are reminiscent of those observed in other physical systems involving 2d lattices. We suggest that the connection between lattice-driven DBDs and other areas of physics may benefit from the further development of models that treat plasma filaments as interacting particles.Comment: 4 pages, 4 figure

Unsupervised Incremental Online Learning and Prediction of Musical Audio Signals

Guided by the idea that musical human-computer interaction may become more effective, intuitive, and creative when basing its computer part on cognitively more plausible learning principles, we employ unsupervised incremental online learning (i.e. clustering) to build a system that predicts the next event in a musical sequence, given as audio input. The flow of the system is as follows: 1) segmentation by onset detection, 2) timbre representation of each segment by Mel frequency cepstrum coefficients, 3) discretization by incremental clustering, yielding a tree of different sound classes (e.g. timbre categories/instruments) that can grow or shrink on the fly driven by the instantaneous sound events, resulting in a discrete symbol sequence, 4) extraction of statistical regularities of the symbol sequence, using hierarchical N-grams and the newly introduced conceptual Boltzmann machine that adapt to the dynamically changing clustering tree in 3) , and 5) prediction of the next sound event in the sequence, given the last n previous events. The system's robustness is assessed with respect to complexity and noisiness of the signal. Clustering in isolation yields an adjusted Rand index (ARI) of 82.7%/85.7% for data sets of singing voice and drums. Onset detection jointly with clustering achieve an ARI of 81.3%/76.3% and the prediction of the entire system yields an ARI of 27.2%/39.2%

Self-organization patterns in electroluminescence of bistable ZnS:Mn thin-film structures

An overview of recent original results concerning self-organized pattern formation in the emission of bistable alternating current ZnS:Mn thin - film electroluminescent structures (TFELS) as a dissipative system is given. The influence of technological factors, affecting the properties TFELS, and driving conditions on both the patterns and the hysteresis of the charge- voltage dependence that is responsible for bistability of the TFELS are considered. The correlation between patterns and the shape of the hysteresis is analyzed. The physical processes with positive and negative feedback, which serve, respectively, as activator and inhibitor in the given dissipative system, are discussed

Transition from Townsend to glow discharge: subcritical, mixed or supercritical

The full parameter space of the transition from Townsend to glow discharge is investigated numerically in one space dimension in the classical model: with electrons and positive ions drifting in the local electric field, impact ionization by electrons ($\alpha$ process), secondary electron emission from the cathode ($\gamma$ process) and space charge effects. We also perform a systematic analytical small current expansion about the Townsend limit up to third order in the total current that fits our numerical data very well. Depending on $\gamma$ and system size pd, the transition from Townsend to glow discharge can show the textbook subcritical behavior, but for smaller values of pd, we also find supercritical or some intermediate ``mixed'' behavior. The analysis in particular lays the basis for understanding the complex spatio-temporal patterns in planar barrier discharge systems.Comment: 12 pages, 10 figures, submitted to Phys. Rev.

Active Learning for Auditory Hierarchy

Much audio content today is rendered as a static stereo mix: fundamentally a fixed single entity. Object-based audio envisages the delivery of sound content using a collection of individual sound ‘objects’ controlled by accompanying metadata. This offers potential for audio to be delivered in a dynamic manner providing enhanced audio for consumers. One example of such treatment is the concept of applying varying levels of data compression to sound objects thereby reducing the volume of data to be transmitted in limited bandwidth situations. This application motivates the ability to accurately classify objects in terms of their ‘hierarchy’. That is, whether or not an object is a foreground sound, which should be reproduced at full quality if possible, or a background sound, which can be heavily compressed without causing a deterioration in the listening experience. Lack of suitably labelled data is an acknowledged problem in the domain. Active Learning is a method that can greatly reduce the manual effort required to label a large corpus by identifying the most effective instances to train a model to high accuracy levels. This paper compares a number of Active Learning methods to investigate which is most effective in the context of a hierarchical labelling task on an audio dataset. Results show that the number of manual labels required can be reduced to 1.7% of the total dataset while still retaining high prediction accuracy

Using a modified Delphi methodology to gain consensus on the use of dressings in chronic wounds management

Objective: Managing chronic wounds is associated with a burden to patients, caregivers, health services and society and there is a lack of clarity regarding the role of dressings in improving outcomes. This study aimed to provide understanding on a range of topics, including: the definition of chronicity in wounds, the burden of illness, clinical outcomes of reducing healing time and the impact of early interventions on clinical and economic outcomes and the role of matrix metalloproteinases (MMPs) in wound healing. Method: A systematic review of the literature was carried out on the role of dressings in diabetic foot ulcer (DFU), and venous leg ulcer (VLU) management strategies, their effectiveness, associated resource use/cost, and quality of life (QoL) impact on patients. From this evidence-base statements were written regarding chronicity in wounds, burden of illness, healing time, and the role of MMPs, early interventions and dressings. A modified Delphi methodology involving two iterations of email questionnaires followed by a face-to-face meeting was used to validate the statements, in order to arrive at a consensus for each. Clinical experts were selected, representing nurses, surgeons, podiatrists, academics, and policy experts. Results: In the first round, 38/47 statements reached or exceeded the consensus threshold of 80% and none were rejected. According to the protocol, any statement not confirmed or rejected had to be modified using the comments from participants and resubmitted. In the second round, 5/9 remaining statements were confirmed and none rejected, leaving 4 to discuss at the meeting. All final statements were confirmed with at least 80% consensus. Conclusion: This modified Delphi panel sought to gain clarity from clinical experts surrounding the use of dressings in the management of chronic wounds. A full consensus statement was developed to help clinicians and policy makers improve the management of patients with these conditions