1,676 research outputs found

    Renormalized Landau Levels and Particle-Hole Symmetry in Graphene

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    In this proceedings paper we report on a calculation of graphene's Landau levels in a magnetic field. Our calculations are based on a self-consistent Hartree-Fock approximation for graphene's massless-Dirac continuum model. We find that because of graphene's chiral band structure interactions not only shift Landau-level energies, as in a non-relativistic electron gas, but also alter Landau level wavefunctions. We comment on the subtle continuum model regularization procedure necessary to correctly maintain the lattice-model's particle hole symmetry properties

    The Effect of Interchannel Time Difference on Localisation in Vertical Stereophony

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    Listening tests were conducted in order to analyse the localisation of band-limited stimuli in vertical stereophony. The test stimuli were seven octave bands of pink noise, with centre frequencies ranging from 125–8000Hz, as well as broadband pink noise. Stimuli were presented from vertically arranged loudspeakers either monophonically or as vertical phantom images, created with the upper loudspeaker delayed with respect to the lower by 0, 0.5, 1, 5 and 10ms (i.e. interchannel time difference). The experimental data obtained showed that localisation under the aforementioned conditions is generally governed by the so-called “pitch-height” effect, with the high frequency stimuli generally being localised significantly higher than the low frequency stimuli for all conditions. The effect of interchannel time difference was found to be significant on localisation judgments for both the 1000-4000Hz octave bands and the broadband pink noise; it is suggested that this was related to the effects of comb filtering. Additionally, no evidence could be found to support the existence of the precedence effect in vertical stereophony

    An analysis of commitment strategies in planning: The details

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    We compare the utility of different commitment strategies in planning. Under a 'least commitment strategy', plans are represented as partial orders and operators are ordered only when interactions are detected. We investigate claims of the inherent advantages of planning with partial orders, as compared to planning with total orders. By focusing our analysis on the issue of operator ordering commitment, we are able to carry out a rigorous comparative analysis of two planners. We show that partial-order planning can be more efficient than total-order planning, but we also show that this is not necessarily so

    The moment of microaggression: The experience of acts of oppression, dehumanization and exploitation

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    After a brief introduction and review of recent literature on microaggressions, a theoretical typology of three sources of social injustice (oppression, dehumanization, and exploitation) contributes to the theorization of the sources of microaggressions. A selected compendium of words and affective phrases generated in classroom exercises illustrates the nature of the experience of the moment of microaggression. Future research on microaggressions as well as evaluation of practice should examine the experience of microaggression, including being subjected to microaggression, initiating such acts, and observing such acts

    HIDING BEHIND THE CLOUDS: EFFICIENT, PRIVACY-PRESERVING QUERIES VIA CLOUD PROXIES

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    This project proposes PriView, a privacy-preserving technique for querying third-party ser- vices from mobile devices. Classical private information retrieval (PIR) schemes are diffi- cult to deploy and use, since they require the target service to be replicated and modified. To avoid this problem, PriView utilizes a novel, proxy-mediated form of PIR, in which the client device fetches XORs of dummy query responses from each of two proxies and combines them to produce the required result. Unlike conventional PIR, PriView does not require the third-party service to be replicated or modified in any way. We evaluated a PriView implementation for the Google Static Maps service utilizing an Android OS front- end and Amazon EC2 proxies. PriView is able to provide tunable confidentiality with low overhead, allowing bandwidth usage, power consumption, and end-to-end latency to scale sublinearly with the provided degree of confidentiality

    A literature-based approach to annotation and browsing of Web resources

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    The emerging Semantic Web technologies critically depend on the availability of shared knowledge representations called ontologies, which are intended to encode consensual knowledge about specific domains. Currently, the proposed processes for building and maintaining those ontologies entail the joint effort of groups of representative domain experts, which can be expensive in terms of co-ordination and in terms of time to reach consensus. In this paper, literature-based ontologies, which can be initially developed by a single expert and maintained continuously, are proposed as preliminary alternatives to group-generated domain ontologies, or as early versions of them. These ontologies encode domain knowledge in the form of terms and relations along with the (formal or informal) bibliographical resources that define or deal with them, which makes them specially useful for domains in which a common terminology or jargon is not soundly established. A general-purpose metamodelling framework for literature-based ontologies - which has been used in two concrete domains - is described, along with a proposed methodology and a specific resource annotation approach. In addition, the implementation of a RDF-based Web resource browser - that uses the ontologies to guide the user in the exploration of a corpus of digital resources- is presented as a proof of concept

    Preferred levels for background ducking to produce esthetically pleasing audio for TV with clear speech

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    In audio production, background ducking facilitates speech intelligibility while allowing the background to fulfill its purpose, e.g., to create ambience, set the mood, or convey semantic cues. Technical details for recommended ducking practices are not currently documented in the literature. Hence, we first analyzed common practices found in TV documentaries. Second, a listening test investigated the preferences of 22 normal-hearing participants on the Loud- ness Difference (LD) between commentary and background during ducking. Highly personal preferences were observed, highlighting the importance of object-based personalization. Sta- tistically significant difference was found between non-expert and expert listeners. On average, non-experts preferred LDs that were 4 LU higher than the ones preferred by experts. A sta- tistically significant difference was also found between Commentary over Music (CoM) and Commentary over Ambience (CoA). Based on the test results, we recommend at least 10 LU difference for CoM and at least 15 LU for CoA. Moreover, a computational method based on the Binaural Distortion-Weighted Glimpse Proportion (BiDWGP) was found to match the median preferred LD for each item with good accuracy (mean absolute error = 1.97 LU ± 2.50)

    Agriculture, Rural Development and Potential for a ‘Middle Agriculture’ in Ireland

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    Working PaperThis paper gives a brief overview of current farm viability in Ireland and summarises some of the main ‘barriers’ to farm families’ engagement in contemporary rural development programmes. Against this backdrop, the paper discusses the potential of a middle agriculture model for rural development. The capacity of such a model to address some of the economic, social and cultural predicaments of Irish family farms is outlined. The potential of the model is also discussed in terms of how it may respond to contemporary EC rural development policy priority objectives
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