Lifshitz-like transition and enhancement of correlations in a rotating bosonic ring lattice

We study the effects of rotation on one-dimensional ultra-cold bosons confined to a ring lattice. For commensurate systems, at a critical value of the rotation frequency, an infinitesimal interatomic interaction energy opens a gap in the excitation spectrum, fragments the ground state into a macroscopic superposition of two states with different circulation and generates a sudden change in the topology of the momentum distribution. These features are reminiscent of the topological changes in the Fermi surface that occurs in the Lifshitz transition in fermionic systems. The entangled nature of the ground state induces a strong enhancement of quantum correlations and decreases the threshold for the Mott insulator transition. In contrast to the commensurate case, the incommensurate lattice is rather insensitive to rotation. Our studies demonstrate the utility of noise correlations as a tool for identifying new physics in strongly correlated systems.Comment: 5 pages, 4 figure

Exploring the characteristics of analytic decomposition of speech signals

This paper investigates the properties of analytic transformation of speech into envelope and phase functions. The envelope is shown to evolve slowly with the pitch of the input speech, whilst the phase consists of two components; one evolving slowly with pitch and another that exhibits a more rapid evolution. We investigate decomposing the phase component further using two distinct methods: (a) filtering of the phase in the pitch evolutionary direction and (b) performing a second analytic decomposition of the phase into secondary envelope and phase components. To examine the characteristics of the pitch cycle evolution, the analytic transform is employed in a waveform interpolation (WI) coding structure. The two phase decompositions are then analysed with particular emphasis on quantisation sensitivity and the required transmission rate. Results indicate that the analytic decomposition may offer a degree of scalability to speech coders, especially when employed in coders that exploit pitch evolution such as WI

Facilitating Universal Multimedia Adaptation (UMA) in a Heterogeneous Peer-to-Peer Network

This paper proposes a P2P architecture which uses MPEG-21 as a standard based technique to dynamically adapt resources according to various usage environment attributes such as terminal capabilities and user preferences. In the architecture, a super peer based approach is used to cluster peers, store peer information, perform searches and instruct peers to adapt/send resources. Pull and push-based adaptation methods are introduced to adapt search results and resources in an intelligent manner based on the usage environment attributes. Simulation results show that the proposed architecture reduces download time while increasing resource availabilities and download speed in the network when compared to traditional P2P systems

Low rate WI SEW representation using a REW-implicit pulse model

Reducing the bit rate of waveform interpolation speech coders while maintaining the perceptual quality has been the focus of a great deal of research. This letter proposes a new method of slowly evolving waveform (SEW) quantization specifically targeted at low rate coding. The proposed method uses a pulse model whose parameters are implicitly contained in the quantized rapidly evolving waveform (REW) parameters, thus requiring no bits for transmission. Results indicate no degradation in perceptual speech quality when compared to that of the existing SEW quantization method. This retention of perceptual quality is in spite of a 12% reduction in the overall coder bit rate

Dynamic multimedia adaptation and updating of media streams with MPEG-21

The paper discusses media streaming using dynamic resource adaptation and update as a means of facilitating universal multimedia access (UMA): the concept of accessing multimedia content through a variety of possible schemes (Bormans, J. et al., IEEE Sig. Process. Magazine, 2003). As background, the paper summarizes the most common content negotiation approaches and addresses their facets and problems. MPEG-21, the multimedia framework and its relationship to UMA are then explained. Our primary focus is an end-to-end approach to content adaptation which takes advantage of MPEG-21 to facilitate the UMA concept in a media streaming environment. The concept is validated using a media streaming test-bed which provides for wide adaptation according to broad usage descriptions

Application of semiconductor industry cleaning technologies for Genesis sample collectors

Genesis array collectors recovered after the sub-nominal landing have been exposed to particulate and molecular contamination. In this study, semiconductor industry based cleaning technologies are being evaluated for their efficacy in contaminant removal

An analysis of the limitations of blind signal separation application with speech

Blind Signal Separation (BSS) techniques are commonly employed in the separation of speech signals, using Independent Component Analysis (ICA) as the criterion for separation. This paper investigates the viability of employing ICA for real-time speech separation (where short frame sizes are the norm). The relationship between the statistics of speech and the assumption of statistical independence (at the core of ICA) is examined over a range of frame sizes. The investigation confirms that statistical independence is not a valid assumption for speech when divided into the short frames appropriate to real-time separation. This is primarily due to the quasi-stationary nature of speech over the temporal short term. We conclude that employing ICA for real-time speech separation will always result in limited performance due to a fundamental failure to meet the strict assumptions of ICA

Varying microphone patterns for meeting speech segmentation using spatial audio cues

Meetings, common to many business environments, generally involve stationary participants. Thus, participant location information can be used to segment meeting speech recordings into each speaker’s ‘turn’. The authors’ previous work proposed the use of spatial audio cues to represent the speaker locations. This paper studies the validity of using spatial audio cues for meeting speech segmentation by investigating the effect of varying microphone pattern on the spatial cues. Experiments conducted on recordings of a real acoustic environment indicate that the relationship between speaker location and spatial audio cues strongly depends on the microphone pattern

Improved signal analysis and time-synchronous reconstruction in waveform interpolation coding

This paper presents a waveform-matched waveform interpolation (WMWI) technique which enables improved speech analysis over existing WI coders. In WMWI, an accurate representation of speech evolution is produced by extracting critically-sampled pitch periods of a time-warped, constant pitch residual. The technique also offers waveform-matching capabilities by using an inverse warping process to near-perfectly reconstruct the residual. Here, a pitch track optimisation technique is described which ensures the speech residual can be effectively decomposed and quantised. Also, the pitch parameters required to efficiently quantise and recreate the pitch track, on a period-by-period basis, are identified. This allows time-synchrony between the original and decoded signals to be preserved

Time delay estimation of reverberant meeting speech: on the use of multichannel linear prediction

Effective and efficient access to multiparty meeting recordings requires techniques for meeting analysis and indexing. Since meeting participants are generally stationary, speaker location information may be used to identify meeting events e.g., detect speaker changes. Time-delay estimation (TDE) utilizing cross-correlation of multichannel speech recordings is a common approach for deriving speech source location information. Research improved TDE by calculating TDE from linear prediction (LP) residual signals obtained from LP analysis on each individual speech channel. This paper investigates the use of LP residuals for speech TDE, where the residuals are obtained from jointly modeling the multiple speech channels. Experiments conducted with a simulated reverberant room and real room recordings show that jointly modeled LP better predicts the LP coefficients, compared to LP applied to individual channels. Both the individually and jointly modeled LP exhibit similar TDE performance, and outperform TDE on the speech alone, especially with the real recordings