Browse ORBi by ORBi project

- Background
- Content
- Benefits and challenges
- Legal aspects
- Functions and services
- Team
- Help and tutorials

Magnetic properties and anisotropy of orthorhombic DyMnO3 single crystal ; ; Fagnard, Jean-François et al in Journal of Magnetism and Magnetic Materials (2013), 335(0), 46-52 An orthorhombic DyMnO3 single crystal has been studied in magnetic fields up to 14 T and between 3 K and room temperature. The field dependent ordering temperature of Dy moments is deduced. The ... [more ▼] An orthorhombic DyMnO3 single crystal has been studied in magnetic fields up to 14 T and between 3 K and room temperature. The field dependent ordering temperature of Dy moments is deduced. The paramagnetic Curie Weiss behavior is related mainly to the Dy3+sublattice whereas the Mn sublattice contribution plays a secondary role. DC magnetization measurements show marked anisotropic features, related to the anisotropic structure of a cubic system stretched along a body diagonal, with a magnetic easy axis parallel to the crystallographic b axis. A temperature and field dependent spin flop transition is observed below 9 K, when relatively weak magnetocrystalline anisotropy is overcome by magnetic fields up to 1.6 T. [less ▲] Detailed reference viewed: 51 (8 ULg)Microwave properties of DyBCO monodomain in the mixed state and comparison with other RE-BCO systems ; ; Ausloos, Marcel et al in Physica C: Superconductivity and its Applications (2011), 471(21-22), 854-858 We report on microwave measurements on DyBa 2Cu 3O 7-δ monodomains grown by the top-seeded melt-textured technique. We measured the field increase of the surface resistance R s(H) in the a-b plane at 48.3 ... [more ▼] We report on microwave measurements on DyBa 2Cu 3O 7-δ monodomains grown by the top-seeded melt-textured technique. We measured the field increase of the surface resistance R s(H) in the a-b plane at 48.3 GHz. Measurements were performed at fixed temperatures in the range 70 K-T c with a static magnetic field μ 0H < 0.8 T parallel to the c-axis. Low field steep increase of the dissipation, typical signature of the presence of weak links, is absent, thus indicating the single-domain behavior of the sample under study. The magnetic field dependence of R s(H) is ascribed to the dissipation caused by vortex motion. The analysis of X s(H) points to a free-flow regime, thus allowing to obtain the vortex viscosity as a function of temperature. We compare the results with those obtained on RE-BCO systems. In particular, we consider strongly pinned films of YBa 2Cu 3O 7-δ with nanometric BaZrO 3 inclusions. © 2011 Elsevier B.V. All rights reserved. [less ▲] Detailed reference viewed: 12 (2 ULg)Magnetic properties of drilled bulk high-temperature superconductors filled with a ferromagnetic powder ; Fagnard, Jean-François ; et al in Superconductor Science and Technology (2011), 24 It is shown that filling the holes of a drilled bulk high-temperature superconductor (HTS) with a soft ferromagnetic powder enhances its trapping properties. The magnetic properties of the trapped field ... [more ▼] It is shown that filling the holes of a drilled bulk high-temperature superconductor (HTS) with a soft ferromagnetic powder enhances its trapping properties. The magnetic properties of the trapped field magnet are characterized by Hall probe mapping and magnetization measurements. This analysis is completed by a numerical model based on a 3D finite-element method where the conductivity of the superconducting material is described by a power law while the permeability of the ferromagnetic material is fixed to a given value and is considered uniform. Numerical results support the experimental observations. In particular, they confirm the increase of trapped flux that is observed with Hall probe mapping after impregnation. [less ▲] Detailed reference viewed: 107 (47 ULg)Numerical Study of the Shielding properties of Macroscopic Hybrid Ferromagnetic/Superconductor Hollow Cylinders Lousberg, Grégory ; Fagnard, Jean-François ; Ausloos, Marcel et al in IEEE Transactions on Applied Superconductivity (2010), 20(1), 33 We study the magnetic shielding properties of hybrid ferromagnetic/superconductor (F/S) structures consisting of two coaxial cylinders, with one of each material.We use an axisymmetric finite-element ... [more ▼] We study the magnetic shielding properties of hybrid ferromagnetic/superconductor (F/S) structures consisting of two coaxial cylinders, with one of each material.We use an axisymmetric finite-element model in which the electrical properties of the superconducting tube are modeled by a nonlinear E-J power law with a magnetic-field-dependent critical current density whereas the magnetic properties of the ferromagnetic material take saturation into account. We study and compare the penetration of a uniform axial magnetic field in two cases: 1) a ferromagnetic tube placed inside a larger superconducting tube (Ferro-In configuration) and 2) a ferromagnetic tube placed outside the superconducting one (Ferro-Out configuration). In both cases, we assess how the ferromagnetic tube improves the shielding properties of the sole superconducting tube. The influence of the geometrical parameters of the ferromagnetic tube is also studied: It is shown that, upon an optimal choice of the geometrical parameters, the range of magnetic fields that are efficiently shielded by the hightemperature superconductor tube alone can be increased by a factor of up to 7 (2) in a Ferro-Out (Ferro-In) configuration. The optimal configuration uses a 1020 carbon steel with a thickness of 2 mm and a height that is half that of the superconducting cylinder (80 mm). [less ▲] Detailed reference viewed: 107 (58 ULg)Modification of the trapped field in bulk HTS as a result of the drilling of a pattern of artificial holes ; Fagnard, Jean-François ; Ausloos, Marcel et al in Journal of Physics: Conference Series (2010), 234 The trapped magnetic field is examined in bulk high-temperature superconductors that are artificially drilled along their c-axis. The influence of the hole pattern on the magnetization is studied and ... [more ▼] The trapped magnetic field is examined in bulk high-temperature superconductors that are artificially drilled along their c-axis. The influence of the hole pattern on the magnetization is studied and compared by means of numerical models and Hall probe mapping techniques. To this aim, we consider two bulk YBCO samples with a rectangular cross-section that are drilled each by six holes arranged either on a rectangular lattice (sample I) or on a centered rectangular lattice (sample II). For the numerical analysis, three different models are considered for calculating the trapped flux: (i), a two-dimensional (2D) Bean model neglecting demagnetizing effects and flux creep, (ii), a 2D finite-element model neglecting demagnetizing effects but incorporating magnetic relaxation in the form of an E – J power law, and, (iii), a 3D finite element analysis that takes into account both the finite height of the sample and flux creep effects. For the experimental analysis, the trapped magnetic flux density is measured above the sample surface by Hall probe mapping performed before and after the drilling process. The maximum trapped flux density in the drilled samples is found to be smaller than that in the plain samples. The smallest magnetization drop is found for sample II, with the centered rectangular lattice. This result is confirmed by the numerical models. In each sample, the relative drops that are calculated independently with the three different models are in good agreement. As observed experimentally, the magnetization drop calculated in the sample II is the smallest one and its relative value is comparable to the measured one. By contrast, the measured magnetization drop in sample (1) is much larger than that predicted by the simulations, most likely because of a change of the microstructure during the drilling process. [less ▲] Detailed reference viewed: 39 (25 ULg)Punctuation effects in english and esperanto texts Ausloos, Marcel in Physica a-Statistical Mechanics and Its Applications (2010), 389(14), 2835-2840 A statistical physics study of punctuation effects on sentence lengths is presented for written texts: Alice in wonderland and Through a looking glass. The translation of the first text into esperanto is ... [more ▼] A statistical physics study of punctuation effects on sentence lengths is presented for written texts: Alice in wonderland and Through a looking glass. The translation of the first text into esperanto is also considered as a test for the role of punctuation in defining a style, and for contrasting natural and artificial, but written, languages. Several log-log plots of the sentence-length-rank relationship are presented for the major punctuation marks. Different power laws are observed with characteristic exponents. The exponent can take a value much less than unity (ca. 0.50 or 0.30) depending on how a sentence is defined. The texts are also mapped into time series based on the word frequencies. The quantitative differences between the original and translated texts are very minutes, at the exponent level. It is argued that sentences seem to be more reliable than word distributions in discussing an author style. (C) 2010 Published by Elsevier B.V. [less ▲] Detailed reference viewed: 8 (1 ULg)Organization of networks with tagged nodes and biased links: A priori distinct communities The case of intelligent design proponents and Darwinian evolution defenders ; Ausloos, Marcel in Physica A: Statistical Mechanics and its Applications (2010), 389(23), 5479-5494 Among the topics of opinion formation it is of interest to observe the characteristics of networks with a priori distinct communities. The citation network(s) between selected members of the ... [more ▼] Among the topics of opinion formation it is of interest to observe the characteristics of networks with a priori distinct communities. The citation network(s) between selected members of the Neocreationist and Intelligent Design and the Darwinian Evolution communities are unfolded through the available internet citations. The resulting adjacency matrix is not symmetric. A generalization of considerations pertaining to the case of networks with tagged nodes and biased links, directed or undirected, is presented. The main characteristic coefficients describing the structure of such networks are outlined. The structural features are discussed searching for statistical aspects of the communities. The degree distributions, each network's assortativity, specific global and local clustering coefficients and the Average Overlap Indices are especially calculated since the distribution of elements in the rectangular submatrices represent inter-community connections. The various closed and open triangles made from nodes, distinguishing the community, are listed. The z-scores of patterns are calculated. One can distinguish between opinion leaders, followers and main rivals and briefly interpret their relationships through intuitively expected behavior in defence of an opinion. Suggestions for more elaborate models describing such communities and their subsequent structures are found in conclusions. (C) 2010 Elsevier B.V. All rights reserved. [less ▲] Detailed reference viewed: 10 (0 ULg)Has the world economy reached its globalization limit? ; Ausloos, Marcel in Physica A: Statistical Mechanics and its Applications (2010), 389(4), 797-806 The economy globalization measure problem is discussed. Four macroeconomic indices of twenty among the "richest" countries are examined. Four types of "distances" are calculated. Two types of networks are ... [more ▼] The economy globalization measure problem is discussed. Four macroeconomic indices of twenty among the "richest" countries are examined. Four types of "distances" are calculated. Two types of networks are next constructed for each distance measure definition. It is shown that the globalization process can be best characterised by an entropy measure, based on entropy Manhattan distance. It is observed that a globalization maximum was reached during the interval 1970-2000. More recently a deglobalization process has been observed. (C) 2009 Elsevier B.V. All rights reserved. [less ▲] Detailed reference viewed: 4 (0 ULg)Dynamic peer-to-peer competition ; ; et al in Physica A: Statistical Mechanics and its Applications (2010), 389(13), 2628-2636 The dynamic behavior of a multiagent system in which the agent size si is variable it is studied along a Lotka-Volterra approach. The agent size has hereby the meaning of the fraction of a given market ... [more ▼] The dynamic behavior of a multiagent system in which the agent size si is variable it is studied along a Lotka-Volterra approach. The agent size has hereby the meaning of the fraction of a given market that an agent is able to capture (market share). A Lotka-Volterra system of equations for prey-predator problems is considered, the competition factor being related to the difference in size between the agents in a one-on-one competition. This mechanism introduces a natural self-organized dynamic competition among agents. In the competition factor, a parameter sigma is introduced for scaling the intensity of agent size similarity, which varies in each iteration cycle. The fixed points of this system are analytically found and their stability analyzed for small systems (with n = 5 agents). We have found that different scenarios are possible, from chaotic to non-chaotic motion with cluster formation as function of the a parameter and depending on the initial conditions imposed to the system. The present contribution aim is to show how a realistic though minimalist nonlinear dynamics model can be used to describe the market competition (companies, brokers, decision makers) among other opinion maker communities. (C) 2010 Elsevier B.V. All rights reserved. [less ▲] Detailed reference viewed: 22 (1 ULg)ENTROPY CORRELATION DISTANCE METHOD APPLIED TO STUDY CORRELATIONS BETWEEN THE GROSS DOMESTIC PRODUCT OF RICH COUNTRIES Ausloos, Marcel ; in International Journal of Bifurcation & Chaos in Applied Sciences & Engineering (2010), 20(2), 381-389 The Theil index is much used in economy and finance; it looks like the Shannon entropy, but pertains to event values rather than to their probabilities. Any time series can be remapped through the Theil ... [more ▼] The Theil index is much used in economy and finance; it looks like the Shannon entropy, but pertains to event values rather than to their probabilities. Any time series can be remapped through the Theil index. Correlation coefficients can be evaluated between the new time series, thereby allowing to study their mutual statistical distance - to be contrasted to the usual correlation distance measure for the primary time series. As an example this entropy-like correlation distance method (ECDM) is applied to the Gross Domestic Product of 20 rich countries in order to test some economy globalization process. Hierarchical distances allow to construct (i) a linear network, (ii) a Locally Minimal Spanning Tree. The role of time averaging in finite size windows is illustrated and discussed. It is also shown that the mean distance between the most developed countries, was decreasing since 1960 till 2000, which we consider to be a proof of globalization of the economy for these countries. [less ▲] Detailed reference viewed: 21 (4 ULg)Structural and magnetic properties of nanosized barium hexaferrite powders obtained by microemulsion technique ; ; Ausloos, Marcel et al in Diffusion and Defect Data--Solid State Data, Pt. B: Solid State Phenomena (2010), 159 Detailed reference viewed: 16 (5 ULg)Magneto-thermal phenomena in bulk high temperature superconductors subjected to applied AC magnetic fields Vanderbemden, Philippe ; Laurent, Philippe ; Fagnard, Jean-François et al in Superconductor Science and Technology (2010), 23 In the present work we study, both theoretically and experimentally, the temperature increase in a bulk high temperature superconductor subjected to applied AC magnetic fields of large amplitude. We ... [more ▼] In the present work we study, both theoretically and experimentally, the temperature increase in a bulk high temperature superconductor subjected to applied AC magnetic fields of large amplitude. We calculate analytically the equilibrium temperatures of the bulk sample as a function of the experimental parameters using a simple critical state model for an infinitely long type-II superconducting slab or cylinder. The results show the existence of a limit heat transfer coefficient (AUlim) separating two thermal regimes with different characteristics. The theoretical analysis predicts a ‘forbidden’ temperature window within which the temperature of the superconductor can never stabilize when the heat transfer coefficient is small. In addition, we determine analytical expressions for two threshold fields Htr1 and Htr2 characterizing the importance of magneto-thermal effects and show that a thermal runaway always occurs when the field amplitude is larger than Htr2. The theoretical predictions of the temperature evolution of the bulk sample during a self-heating process agree well with the experimental data. The simple analytical study presented in this paper enables order of magnitude thermal effects to be estimated for simple superconductor geometries under applied AC magnetic fields and can be used to predict the influence of experimental parameters on the self-heating characteristics of bulk type-II superconductors. [less ▲] Detailed reference viewed: 94 (51 ULg)Pulsed-field magnetization of drilled bulk high-temperature superconductors: flux front propagation in the volume and on the surface Lousberg, Grégory ; Fagnard, Jean-François ; et al in Superconductor Science and Technology (2009), (22), 125026 We present a method for characterizing the propagation of the magnetic flux in an artificially drilled bulk high-temperature superconductor (HTS) during pulsed-field magnetization. As the magnetic pulse ... [more ▼] We present a method for characterizing the propagation of the magnetic flux in an artificially drilled bulk high-temperature superconductor (HTS) during pulsed-field magnetization. As the magnetic pulse penetrates the cylindrical sample, the magnetic flux density is measured simultaneously in 16 holes by means of microcoils that are placed across the median plane, i.e. at an equal distance from the top and bottom surfaces, and close to the surface of the sample. We discuss the time evolution of the magnetic flux density in the holes during a pulse and measure the time taken by the external magnetic flux to reach each hole. Our data show that the flux front moves faster in the median plane than on the surface when penetrating the sample edge; it then proceeds faster along the surface than in the bulk as it penetrates the sample further. Once the pulse is over, the trapped flux density inside the central hole is found to be about twice as large in the median plane as on the surface. This ratio is confirmed by modelling. [less ▲] Detailed reference viewed: 69 (42 ULg)Magnetic shielding properties of high- Tc superconducting hollow cylinders: model combining experimental data for axial and transverse magnetic field configurations Fagnard, Jean-François ; ; Ausloos, Marcel et al in Superconductor Science and Technology (2009), 22(10), 10500210 Magnetic shielding efficiency was measured on high- Tc superconducting hollow cylinders subjected to either an axial or a transverse magnetic field in a large range of field sweep rates, dBapp/dt. The ... [more ▼] Magnetic shielding efficiency was measured on high- Tc superconducting hollow cylinders subjected to either an axial or a transverse magnetic field in a large range of field sweep rates, dBapp/dt. The behaviour of the superconductor was modelled in order to reproduce the main features of the field penetration curves by using a minimum number of free parameters suitable for both magnetic field orientations. The field penetration measurements were carried out on Pb-doped Bi-2223 tubes at 77 K by applying linearly increasing magnetic fields with a constant sweep rate ranging between 10 uT s[?]1 and 10 mT s[?]1 for both directions of the applied magnetic field. The experimental curves of the internal field versus the applied field, Bin(Bapp), show that, at a given sweep rate, the magnetic field for which the penetration occurs, Blim, is lower for the transverse configuration than for the axial configuration. A power law dependence with large exponent, n', is found between Blim and dBapp/dt. The values of n' are nearly the same for both configurations. We show that the main features of the curves Bin(Bapp) can be reproduced using a simple 2D model, based on the method of Brandt, involving a E(J) power law with an n-exponent and a field-dependent critical current density, Jc(B), (following the Kim model: Jc = Jc0(1+B/B1)[?]1). In particular, a linear relationship between the measured n'-exponents and the n-exponent of the E(J) power law is suggested by taking into account the field dependence of the critical current density. Differences between the axial and the transverse shielding properties can be simply attributed to demagnetizing fields. [less ▲] Detailed reference viewed: 113 (48 ULg)DC and AC Shielding Properties of Bulk High-Tc Superconducting Tubes Fagnard, Jean-François ; ; Lousberg, Grégory et al in IEEE Transactions on Applied Superconductivity (2009), 19(3), 2905-2908 We have studied numerically and experimentally the magnetic flux penetration in high-Tc superconducting tube subjected to a uniform magnetic field parallel to its long axis. This study is carried in view ... [more ▼] We have studied numerically and experimentally the magnetic flux penetration in high-Tc superconducting tube subjected to a uniform magnetic field parallel to its long axis. This study is carried in view of designing low-frequency magnetic shields by exploiting the diamagnetic properties of high-Tc superconducting ceramics. We have measured the field attenuation for applied magnetic fields in the frequency range 5 mHz-0.1 Hz by Hall probe measurements and at audio frequencies using a sensing coil. A simple 1D analysis using the Kim critical state model was found to be able to reproduce the experimental data satisfactorily. We have also determined the phase shift between the internal and the applied field both experimentally and numerically. Finally, we have studied the sweep rate dependence of the magnetic shielding properties, using data recorded either at several constant sweep rates dB/dt or at several AC fields of various amplitudes and frequencies. Both methods agree with each other and lead to a n -value of the E ~ J n law equal to ~ 40 at 77 K. [less ▲] Detailed reference viewed: 159 (63 ULg)Numerical simulation of the magnetization of high-temperature superconductors: a 3D finite element method using a single time-step iteration Lousberg, Grégory ; Ausloos, Marcel ; Geuzaine, Christophe et al in Superconductor Science and Technology (2009), 22 In this paper, we report progress towards a 3D finite element model for the magnetization of a high-temperature superconductor (HTS): we suggest a method that takes into account a power law conductivity ... [more ▼] In this paper, we report progress towards a 3D finite element model for the magnetization of a high-temperature superconductor (HTS): we suggest a method that takes into account a power law conductivity and demagnetization effects, while neglecting the effects associated with currents that are not perpendicular to the local magnetic induction. We consider samples that are subjected to a uniform magnetic field varying linearly with time. Their magnetization is calculated by means of a weak formulation in the magnetostatic approximation of the Maxwell equations (A–φ formulation). An implicit method is used for the temporal resolution (backward Euler scheme) and is solved with the open source solver GetDP. Fixed point iterations are used to deal with the power law conductivity of HTS. The finite element formulation is validated for an HTS tube with large n value by comparing with results obtained with other well-established methods. We show that carrying out the calculations with a single time-step (as opposed to many small time-steps) produces results with excellent accuracy in a drastically reduced simulation time. The numerical method is extended to the study of the trapped magnetization of cylinders that are drilled with different arrays of columnar holes arranged parallel to the cylinder axis. [less ▲] Detailed reference viewed: 173 (57 ULg)Measurement of the magnetic field inside the holes of a drilled bulk high-Tc superconductor Lousberg, Grégory ; Fagnard, Jean-François ; et al in Superconductor Science and Technology (2009), 22 We use macroscopic holes drilled in a bulk YBCO superconductor to probe its magnetic properties in the volume of the sample. The sample is subjected to an AC magnetic flux with a density ranging from 30 ... [more ▼] We use macroscopic holes drilled in a bulk YBCO superconductor to probe its magnetic properties in the volume of the sample. The sample is subjected to an AC magnetic flux with a density ranging from 30 to 130 mT and the flux in the superconductor is probed by miniature coils inserted in the holes. In a given hole, three different penetration regimes can be observed: (i) the shielded regime, where no magnetic flux threads the hole; (ii) the gradual penetration regime, where the waveform of the magnetic field has a clipped sine shape whose fundamental component scales with the applied field; and (iii) the flux concentration regime, where the waveform of the magnetic field is nearly a sine wave, with an amplitude exceeding that of the applied field by up to a factor of two. The distribution of the penetration regimes in the holes is compared with that of the magnetic flux density at the top and bottom surfaces of the sample, and is interpreted with the help of optical polarized light micrographs of these surfaces. We show that the measurement of the magnetic field inside the holes can be used as a local characterization of the bulk magnetic properties of the sample. [less ▲] Detailed reference viewed: 120 (82 ULg)Statistical mechanics approach to a reinforcement learning model with memory ; ; Ausloos, Marcel in Physica A: Statistical Mechanics and its Applications (2009), 388(9), 1849-1856 We introduce a two-player model of reinforcement learning with memory. Past actions of an iterated game are stored in a memory and used to determine player's next action. To examine the behaviour of the ... [more ▼] We introduce a two-player model of reinforcement learning with memory. Past actions of an iterated game are stored in a memory and used to determine player's next action. To examine the behaviour of the model some approximate methods are used and confronted against numerical simulations and exact master equation. When the length of memory of players increases to infinity the model undergoes ail absorbing-state phase transition. Performance of examined strategies is checked in the prisonor' dilemma game. It turns out that it is advantageous to have a large memory in symmetric games, but it is better to have a short memory in asymmetric ones. (C) 2009 Elsevier B.V. All rights reserved. [less ▲] Detailed reference viewed: 12 (0 ULg)Effects of Rice Straw on the Color and Microstructure of Bizen, a Traditional Japanese Stoneware, as a Function of Oxygen Partial Pressure ; ; et al in Journal of the American Ceramic Society (2009), 92(8), 1840-1844 The effects of oxygen partial pressure during thermal treatment on the color and microstructure of Bizen, a traditional Japanese stoneware, were studied through model experiments using clay pellets ... [more ▼] The effects of oxygen partial pressure during thermal treatment on the color and microstructure of Bizen, a traditional Japanese stoneware, were studied through model experiments using clay pellets covered lightly with rice straw as a coloring assistant. When heated in flowing nitrogen, the model pellet turned blackish owing to the formation of alpha-Fe particles coated with graphite. However, schreibersite (Fe3P), which is also blackish, was formed specifically on the pellet surface in direct contact with the straw. The rice straw seems to have generated a strongly reducing atmosphere, strong enough for the metallization to alpha-Fe, and also to have provided phosphorus through contact. When oxygen content in the surrounding gas atmosphere was raised to N-2/O-2=99/1, the pellet surface turned yellowish brown because the main coloring material was Fe3+-containing mullite. At oxygen contents of N-2/O-2=98/2 or more, the formation of hematite (alpha-Fe2O3) pushed the color to deep red. [less ▲] Detailed reference viewed: 14 (0 ULg)Organizational and dynamical aspects of a small network with two distinct communities: Neo-creationists vs. Evolution Defenders ; Ausloos, Marcel in Scientometrics (2009), 80(2), 457-472 Social impacts and degrees of organization inherent to opinion formation for interacting agents on networks present interesting questions of general interest from physics to sociology. We present a ... [more ▼] Social impacts and degrees of organization inherent to opinion formation for interacting agents on networks present interesting questions of general interest from physics to sociology. We present a quantitative analysis of a case implying an evolving small size network, i.e. that inherent to the ongoing debate between modern creationists (most are Intelligent Design (ID) proponents (IDP) and Darwin's theory of Evolution Defenders (DED)). This study is carried out by analyzing the structural properties of the citation network unfolded in the recent decades by publishing works belonging to members of the two communities. With the aim of capturing the dynamical aspects of the interaction between the IDP and DED groups, we focus on two key quantities, namely, the degree of activity of each group and the corresponding degree of impact on the intellectual community at large. A representative measure of the former is provided by the rate of production of publications (RPP), whilst the latter can be assimilated to the rate of increase in citations (RIC). These quantities are determined, respectively, by the slope of the time series obtained for the number of publications accumulated per year and by the slope of a similar time series obtained for the corresponding citations. The results indicate that in this case, the dynamics can be seen as geared by triggered or damped competition. The network is a specific example of marked heterogeneity in exchange of information activity in and between the communities, particularly demonstrated through the nodes having a high connectivity degree, i.e. opinion leaders. [less ▲] Detailed reference viewed: 10 (0 ULg) |
||