7,258 research outputs found
Influence of ac ageing on space charge dynamics in LDPE
No full textPolymeric materials have been widely used as insulation in power industry due to their excellent electrical properties. However, these properties deteriorate in time irreversibly when the material is subjected to electric stress. Although space charge is believed to play an important role in ac ageing, exact mechanisms are poorly understood due to very limited experimental data. In the present work efforts have been made to investigate the influence of ac ageing on space charge dynamics in low-density polyethylene (LDPE). LDPE films with 200mm were aged at 50 kV/mm at 50 Hz for various times at ambient temperature. Space charge dynamics in the samples prior to and after ageing were monitored using the pulsed electroacoustic (PEA) technique under dc electric stress. The results indicate that there is a significant amount of homocharge accumulation in the unaged sample due to charge injection. These injected charges are the captured by the deep traps originated from the interface between crystalline and amorphous regions in LDPE. Ageing under ac condition does not necessarily lead to an increase in amount of charge in the bulk but leads to an increase in mobility of charge carriers. Chemical analysis by infrared spectroscope (FTIR) reveals there are chemical changes taken place in the bulk of the material after ac ageing. It is believed that the chemical changes introduce shallow traps which promote the movement of charge carriers in the bulk. Consequently, the injected charges spread across the sample
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Enhanced colour encoding of materials discrimination information for multiple view dual-energy x-ray imaging
No full textThis thesis reports an investigation into dual-energy X-ray discrimination techniques. These techniques are designed to provide colour-coded materials discrimination information in a sequence of perspective images exhibiting sequential parallax. The methods developed are combined with a novel 3D imaging technique employing depth from motion or kinetic depth effect (KDE). This technique when applied to X-ray images is termed KDEX imaging and was developed previously by the university team for luggage screening applications at security checkpoints. A primary motivation for this research is that the dual-energy X-ray techniques, which are routinely incorporated into ‘standard’ 2D luggage scanners, provide relatively crude materials discrimination information. In this work it was critical that robust materials discrimination and colour encoding process was implemented as the sequential parallax exhibited by the KDEX imagery may introduce colour changes, due to the different X-ray beam paths associated with each perspective image. Any introduction of ‘colour noise’ into the resultant image sequences could affect the perception of depth and hinder the ongoing assessment of the potential utility of the dual-energy KDEX technique. Two dual-energy discrimination methods have been developed, termed K-II and W-E respectively. Employing the total amount of attenuation measured at each energy level and the weight fraction of layered structures, a combination of the K-II and the W-E techniques enables the computation and extraction of a target objects’ effective atomic number (Zeff) and its surface density (ρS) in the presence of masking layers
Data for Hollow-core fibres for temperature-insensitive fibre optics and its demonstration in an Optoelectronic oscillator
No full textThis dataset contains data (X and Y data with labels and units) that was used to plot the graphs in the journal paper 'Hollow-core fibres for temperature-insensitive fibre optics and its demonstration in an Optoelectronic oscillator'
Journal: Scientific Reports
Authors: U.S. Mutugala, E.R. Numkam Fokoua, Y. Chen, T. Bradley, S. R. Sandoghchi, G.T. Jasion, R. Curtis, M.N. Petrovich, F. Poletti, D.J. Richardson, and R. Slavík</span
Understanding the internal structures of X(4140), X(4274), X(4500) and X(4700)
No full textWe investigate the newly observed X(4500) and X(4700) based on the diquark-antidiquark configuration within the framework of QCD sum rules. Both of them may be interpreted as the D-wave tetraquark states of , but with opposite color structures, which is remarkably similar to the result obtained in Chen and Zhu (Phys Rev D 83:034010, 2011) that X(4140) and X(4274) can be both interpreted as the S-wave tetraquark states of , also with opposite color structures. However, the extracted masses and these suggested assignments to these X states do depend on these running quark masses where MeV and GeV. As a byproduct, the masses of the hidden-bottom partner states of X(4500) and X(4700) are extracted to be both around 10.64 GeV, which can be searched for in the invariant mass distribution.Natural Sciences and Engineering Research Council of Canada (NSERC); National Natural Science Foundation of China [11205011, 11375024, 11222547, 11175073, 11575008, 11261130311]; Ministry of Education of China (the Fundamental Research Funds for the Central Universities), 973 program; National Youth Top-notch Talent Support Program ("Thousands-of-Talents Scheme")SCI(E)ARTICLE37
Baryon fields with U-L(3) x U-R(3) chiral symmetry. III. Interactions with chiral [(3, (3)over-bar) circle plus ((3)over-bar, 3)] spinless mesons
No full textThree-quark nucleon interpolating fields in QCD have well-defined SUL(3) x SUR(3) and U-A(1) chiral transformation properties, viz. left perpendicular(6, 3) circle plus (3, 6)right perpendicular, left perpendicular(3, (3) over bar) circle plus ((3) over bar, 3)right perpendicular, left perpendicular(8, 1) circle plus (1, 8)right perpendicular, and their mirror images; see [H. X. Chen, V. Dmitrasinovic, A. Hosaka, K. Nagata, and S. L. Zhu, Phys. Rev. D 78, 054021 (2008)]. It has been shown (phenomenologically) in [H. X. Chen, V. Dmitrasinovic, and A. Hosaka, Phys. Rev. D 81, 054002 (2010)] that mixing of the left perpendicular(6, 3) circle plus (3, 6)right perpendicular chiral multiplet with one ordinary (naive) and one mirror field belonging to the [(3, (3) over bar) circle plus ((3) over bar, 3)], [(8, 1) circle plus (1, 8)] multiplets can be used to fit the values of the isovector (g(A)((3))) and the flavor-singlet (isoscalar) axial coupling (g(A)((0))) of the nucleon and then predict the axial F and D coefficients, or vice versa, in reasonable agreement with experiment. In an attempt to derive such mixing from an effective Lagrangian, we construct all SUL(3) x SUR(3) chirally invariant non-derivative one-meson-baryon interactions and then calculate the mixing angles in terms of baryons' masses. It turns out that there are (strong) selection rules: for example, there is only one nonderivative chirally symmetric interaction between J = 1/2 fields belonging to the [(6, 3) circle plus (3, 6)] and the [(3, (3) over bar) circle plus ((3) over bar, 3)] chiral multiplets, that is also U-A(1) symmetric. We also study the chiral interactions of the [(3, (3) over bar) circle plus ((3) over bar, 3)] and [(8, 1) circle plus (1, 8)] nucleon fields. Again, there are selection rules that allow only one off-diagonal nonderivative chiral SUL(3) x SUR(3) interaction of this type, that also explicitly breaks the U-A(1) symmetry. We use this interaction to calculate the corresponding mixing angles in terms of baryon masses and fit two lowest-lying observed nucleon (resonance) masses, thus predicting the third (J = 1/2, I = 3/2) Delta resonance, as well as one or two flavor-singlet Lambda hyperon(s), depending on the type of mixing. The effective chiral Lagrangians derived here may be applied to high density matter calculations.Astronomy & AstrophysicsPhysics, Particles & FieldsSCI(E)6ARTICLE1null8
X(4140), X(4270), X(4500), and X(4700) and their cs(c)over-bar (s)over-bar tetraquark partners
No full textIn the simple color-magnetic interaction model, we investigate possible ground cs (c) over bar (s) over bar tetraquark states in the diquark-antidiquark basis. We use several methods to estimate the mass spectrum and discuss possible assignment for the X states observed in the J/psi phi channel. We find that assigning the Belle X(4350) as a 0(++) tetraquark is consistent with the tetraquark interpretation for the X(4140) and X(4270) while the interpretation of the X(4500) and X(4700) needs orbital or radial excitation. There probably exist several tetraquarks around 4.3 GeV that decay into J/psi phi or eta(c)phiNational Natural Science Foundation of China [11175073, 11275115, 11222547, 11575008, 11261130311]; Fundamental Research Funds for the Central Universities; 973 program; National Program for Support of Youth Top-Notch ProfessionalsSCI(E)[email protected]; [email protected]; [email protected]
Baryon fields with UL(3) X UR(3) chiral symmetry: Axial currents of nucleons and hyperons
No full textWe use the conventional F and D octet and decimet generator matrices to reformulate chiral properties of local (nonderivative) and one-derivative nonlocal fields of baryons consisting of three quarks with flavor SU(3) symmetry that were expressed in SU(3) tensor form by Chen et al. [Phys. Rev. D 78, 054021 (2008)]. We show explicitly the chiral transformations of the [(6, 3) circle plus (3, 6)] chiral multiplet in the "SU(3) particle basis,'' for the first time to our knowledge, as well as those of the (3, (3) over bar) circle plus ((3) over bar, 3), (8, 1) circle plus (1, 8) multiplets, which have been recorded before by Bardeen and Lee [ Phys. Rev. 177, 2389 (1969)] and Lee [Phys. Rev. 170, 1359 (1968)]. We derive the vector and axial-vector Noether currents, and show explicitly that their zeroth (chargelike) components close the SU(L) X SU(R) (3) chiral algebra. We use these results to study the effects of mixing of (three-quark) chiral multiplets on the axial current matrix elements of hyperons and nucleons. We show, in particular, that there is a strong correlation, indeed a definite relation between the flavor-singlet (i.e. the zeroth), the isovector (the third), and the eighth flavor component of the axial current, which is in decent agreement with the measured ones.Astronomy & AstrophysicsPhysics, Particles & FieldsSCI(E)10ARTICLE5null8
Note on the generalization of the global embedding Minkowski spacetime approach
No full textThis paper is a supplement of our earlier work [H.-Z. Chen, Y. Tian, Y.-H. Gao, and X.-C. Song, J. High Energy Phys. 10 (2004) 011.]. We map the vector potential of charged black holes into GEMS and find that its effect on the thermal spectrum is the same as that on the black hole side, i.e., it will induce a chemical potential in the thermal spectrum which is the same as that in the charged black holes. We also argue that the generalization of GEMS approach to nonstationary motions is not possible.Astronomy & AstrophysicsPhysics, Particles & FieldsSCI(E)0ARTICLE10null7
X-efficiency Analysis of Commercial Banks in Pakistan: A Preliminary Investigation
Get PDFThe emergence of a fast-paced dynamic environment in the business world in general, and in the financial services sector in particular, has highlighted the significance of competition and efficiency. The need for deregulation has become a touchstone of success in fostering both competition and efficiency especially in the economies, which are exposed to structural reforms. In addition to that, intense competition both among domestic and foreign banks, rapid speed of innovations and introduction of new financial instruments, changing consumer’s demands and desire for product augmentation have changed the way a bank conducts business and services its customers. Larger the degree of competition, it is perceived that the firms would become more efficient. However, when the structure of an industry is product of the government regulations, the degree of competition is impaired markedly implying that the efficiency suffers negatively. Banking industry acts as life-blood of modern trade and commerce acting as a bridge to provide a major source of financial intermediation. Thus, appraisal of its efficiency is vital in context of an efficient and competitive financial system. Study of x-efficiency is believed to be important in particular as Berger, et al. (1993) found that x-inefficiencies account for around 20 percent or more of banking costs. Similarly, recent drive among banks towards downsizing, rightsizing and rationalisation of banking costs also implicates for the assessment of x-efficiency analysis of banks. It becomes vital in Pakistani context as there appears to be no study in literature on efficiency or x-efficiency analysis of banks in Pakistan. “A great deal more work is needed on x-efficiency research in banking. Managerial efficiency, the concept of x-efficiency, appears to be a much more important strategic and policy consideration” [Molyneux, et al. (1960), p. 273]. Given
Author Co-Citation Analysis (ACA): a powerful tool for representing implicit knowledge of scholar knowledge workers
Get PDFIn the last decade, knowledge has emerged as one of the most important and valuable organizational assets. Gradually this importance caused to emergence of new discipline entitled ―knowledge management‖. However one of the major challenges of knowledge management is conversion implicit or tacit knowledge to explicit knowledge. Thus Making knowledge visible so that it can be better accessed, discussed, valued or generally managed is a long-standing objective in knowledge management. Accordingly in this paper author co- citation analysis (ACA) will be proposed as an efficient technique of knowledge visualization in academia (Scholar knowledge workers)
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