252,627 research outputs found

    Driving Operators Relevant: A Feature of Chern-Simons Interaction

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    By computing anomalous dimensions of gauge invariant composite operators (ĻˆĖ‰Ļˆ)n(\bar\psi\psi)^n and (Ļ•āˆ—Ļ•)n(\phi^*\phi)^n in Chern-Simons fermion and boson models, we address that Chern-Simons interactions make these operators more relevant or less irrelevant in the low energy region. We obtain a critical Chern-Simons fermion coupling, 1Īŗc2=619{1\over \kappa_c^2} = {6\over 19}, for a phase transition at which the leading irrelevant four-fermion operator (ĻˆĖ‰Ļˆ)2(\bar\psi\psi)^2 becomes marginal, and a critical Chern-Simons boson coupling, 1Īŗc2=634{1\over \kappa_c^2} = {6\over 34}, for a similar phase transition for the leading irrelevant operator (Ļ•āˆ—Ļ•)4(\phi^*\phi)^4. We see this phenomenon also in the 1/N1/N expansion.Comment: (ten pages, latex, figures included

    Equivalence of Several Chern-Simons Matter Models

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    Not only does Chern-Simons (CS) coupling characterize statistics, but also spin and scaling dimension of matter fields. We demonstrate spin transmutation in relativistic CS matter theory, and moreover show equivalence of several models. We study CS vector model in some details, which provide consistent check to the assertion of the equivalence.Comment: latex, 7page, IFT-478-UNC/NUP-A-93-15 A version within the length limit for Phys. Rev. Letts (in press

    Unsupervised Motion Artifact Detection in Wrist-Measured Electrodermal Activity Data

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    One of the main benefits of a wrist-worn computer is its ability to collect a variety of physiological data in a minimally intrusive manner. Among these data, electrodermal activity (EDA) is readily collected and provides a window into a person's emotional and sympathetic responses. EDA data collected using a wearable wristband are easily influenced by motion artifacts (MAs) that may significantly distort the data and degrade the quality of analyses performed on the data if not identified and removed. Prior work has demonstrated that MAs can be successfully detected using supervised machine learning algorithms on a small data set collected in a lab setting. In this paper, we demonstrate that unsupervised learning algorithms perform competitively with supervised algorithms for detecting MAs on EDA data collected in both a lab-based setting and a real-world setting comprising about 23 hours of data. We also find, somewhat surprisingly, that incorporating accelerometer data as well as EDA improves detection accuracy only slightly for supervised algorithms and significantly degrades the accuracy of unsupervised algorithms.Comment: To appear at International Symposium on Wearable Computers (ISWC) 201

    Simultaneous space charge and conduction current measurements in solid dielectrics under high dc electric field

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    The importance of space charge in solid dielectrics has been recognized for many years and various attempts have been made to map the distribution and assess its influence on the electrical performance of solid dielectrics. Significant development in non-destructive measurement techniques emerged two decades ago. Crosslinked polyethylene (XLPE) has been used for ac power cable insulation up to 500 kV for many years. There is a tendency to use XLPE for dc power cable. However, the easy formation of space charge under dc electric field within XLPE is a major concern for such an application. Space charge in insulation can distort electric field distribution, causing electric field increase in one region and reduction in another. The electric field enhancement could lead to degradation and result in premature failure. Electrical treeing in solid dielectrics is a typical example of local field enhancement due to space charge accumulation. In this report several popular non-destructive techniques are briefly reviewed. This is followed by detailed description of a modified pulsed electroacoustic (PEA) technique that allows simultaneous measurement of space charge and conduction current in a solid dielectric subjected to high dc electric fields. Finally, we report the relationship between space charge dynamics and electrical conduction current in XLPE using the modified PEA system. The effect of electrode material on both charge dynamics and current has been investigated using semiconducting material and aluminium. It has been found charge dynamics in the material depend on electrode configuration. More importantly, it has been noticed that the so called space charge limited transient current peaks are closely related to the meetings of negative and positive charge front in the bulk of the sample

    The Fluctuating Pressure Field in a Supersonic Turbulent Boundary Layer

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    The fluctuating pressure field in a supersonic turbulent boundary laye

    Organisational change and development of reformed Chinese township and village enterprises

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    This article is (c) Emerald Group Publishing and permission has been granted for this version to appear here (http://bura.brunel.ac.uk/handle/2438/8263). Emerald does not grant permission for this article to be further copied/distributed or hosted elsewhere without the express permission from Emerald Group Publishing Limited.Purpose ā€“ This paper aims to investigate the organisational changes (OCs) and the development of Chinese reformed township and village enterprises (RTVEs), their marketing and R&D strategies, and the impact of changes in terms of overall performance. Design/methodology/approach ā€“ A case study methodology involving semi-structured interviews is adopted. The unit chosen is the Guotai International Group (GTIG) in Zhangjiagang, Suzhou, Jiangsu province, China, in which the organisational changes over a period of over 40 years are analysed. Findings ā€“ OCs in Chinese RTVEs are found to be driven by a combination of local government plans and market forces. Considering the hybrid nature of the organisation and ownership structures, changes in Chinese RTVEs follow a very much ā€œtop-downā€ approach. Research limitations/implications ā€“ The findings imply that managers appointed by the state in RTVEs usually lack the necessary skills in marketing and business management, and can be resistant to organisational changes, such as the willingness to undertake risks. As a result, RTVEs may become stuck in a cycle of low-cost, low-tech products, inhibiting any breakthrough in developing their own quality brands. Originality/value ā€“ This is one of few papers studying change over a long span of time to arrive at research findings that will be useful to academic researchers in their future work. The qualitative findings from this paper would also enrich the literatures on organisational change in Chinese RTVEs

    Computation of turbulent flows using an extended k-epsilon turbulence closure model

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    An extended kappa-epsilon turbulence model is proposed and tested with successful results. An improved transport equation for the rate of dissipation of the turbulent kinetic energy, epsilon, is proposed. The proposed model gives more effective response to the energy production rate than does the standard kappa-epsilon turbulence model. An extra time scale of the production range is included in the dissipation rate equation. This enables the present model to perform equally well for several turbulent flows with different characteristics, e.g., plane and axisymmetric jets, turbulent boundary layer flow, turbulent flow over a backward-facing step, and a confined turbulent swirling flow. A second-order accurate finite difference boundary layer code and a nearly second-order accurate finite difference elliptic flow solver are used for the present numerical computations

    Crossover from Kramers to phase-diffusion switching in hysteretic DC-SQUIDs

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    We have measured and propose a model for switching rates in hysteretic DC-SQUID in the regime where phase diffusion processes start to occur. We show that the switching rates in this regime are smaller than the rates given by Kramers' formula due to retrapping of Josephson phase. The retrapping process, which is affected by the frequency dependent impedance of the environment of the DC-SQUID, leads to a peaked second moment of the switching distribution as a function of temperature. The temperature where the peaks occur are proportional to the critical current of the DC- SQUID.Comment: 4 pages, 4 figure

    Adsorption/desorption and electrically controlled flipping of ammonia molecules on graphene

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    In this paper, we evaluate of the adsorption/ desorption of ammonia molecules on a graphene surface by studying the Fermi level shift. Based on a physically plausible model, the adsorption and desorption rates of ammonia molecules on graphene have been extracted from the measured Fermi level shift as a function of exposure time. An electric field-induced flipping behavior of ammonia molecules on graphene is suggested, based on field effect transistor (FET) measurements
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