References of "Bougrine, Hassan"
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See detailSubfield effects on the core of coauthors
Bougrine, Hassan ULg

in Scientometrics (2014), 98(1047-1064),

It is examined whether the number (J) of (joint) publications of a "main scientist" with her/his coauthors ranked according to rank (r) importance, i.e. J ∝ 1/r, as found by Ausloos (Scientometrics 95 ... [more ▼]

It is examined whether the number (J) of (joint) publications of a "main scientist" with her/his coauthors ranked according to rank (r) importance, i.e. J ∝ 1/r, as found by Ausloos (Scientometrics 95:895–909, 2013) still holds for subfields, i.e. when the "main scientist" has worked on different, sometimes overlapping, subfields. Two cases are studied. It is shown that the law holds for large subfields. As shown, in an Appendix, is also useful to combine small topics into large ones for better statistics. It is observed that the sub-cores are much smaller than the overall coauthor core measure. Nevertheless, the smallness of the core and sub-cores may imply further considerations for the evaluation of team research purposes and activities. [less ▲]

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See detailAnalysis of experimental conditions for simultaneous measurements of transport and magnetotransport coefficients of high temperature superconductors
Mucha, J.; Dorbolo, Stéphane ULg; Bougrine, Hassan ULg et al

in Cryogenics (2004), 44(3), 145-149

Experimental conditions for simultaneous measurements of transport coefficients of high temperature superconductors in zero and non-zero magnetic fields are analysed. Test measurements of the thermal ... [more ▼]

Experimental conditions for simultaneous measurements of transport coefficients of high temperature superconductors in zero and non-zero magnetic fields are analysed. Test measurements of the thermal conductivity, the thermoelectric power and the Nernst-Ettingshausen effect of a textured Bi2212 sample are reported in an external magnetic field of 2 T. Errors related to parameters of the thermocouple used and to the spurious heat flows are discussed for a new experimental set-up built based on a closed cycle helium refrigerator. Possible optimising of experimental conditions is suggested. (C) 2003 Elsevier Ltd. All rights reserved. [less ▲]

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See detailLe dépôt et la délivrance du brevet
Bougrine, Hassan ULg

in Cahiers de la Documentation = Bladen voor Documentatie (2001), (N/r1), 5-10

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See detailMagnetic properties of magnetically textured Bi-2212 ceramics
Vanderbemden, Philippe ULg; Bougrine, Hassan ULg; Ausloos, Marcel ULg et al

in Physica C: Superconductivity (2001), 351(1), 67-70

This paper aims at reporting magnetic properties of bulk polycrystalline Bi2Sr2Ca0.8Dy0.2Cu2O8-y samples textured under a magnetic field. The microstructure of these materials is highly anisotropic and ... [more ▼]

This paper aims at reporting magnetic properties of bulk polycrystalline Bi2Sr2Ca0.8Dy0.2Cu2O8-y samples textured under a magnetic field. The microstructure of these materials is highly anisotropic and exhibits particular features needed to be taken into account in order to interpret their magnetic and electrical properties. First the AC magnetic susceptibility has been measured for several magnetic fields (H parallel to ab and H parallel to c) and compared to the electrical resistivity data. The structure of the chi'' peak is shown to be related to the chemical content distribution of the superconducting grains. Next, the magnetic flux profiles have been extracted from the magnetic measurements using the Campbell-Rollins procedure. The anisotropy of the flux profiles and their peculiar curvature behaviour for H parallel toc point out the role of both grain platelet structure and the presence of secondary phases. From these results, we conclude that the magnetic properties of such magnetically textured materials do not allow for a reliable extraction of the critical current density J(c) but essentially probe geometric effects. Such effects have to be taken into account for improving the manufacture of attractive high-T-c materials. (C) 2001 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailSimultaneous measurements of thermal diffusivity, thermal conductivity and thermopower with application to copper and ceramic superconductors
Bougrine, Hassan ULg; Geys, J. F.; Dorbolo, Stéphane ULg et al

in European Physical Journal B -- Condensed Matter (2000), 13(3), 437-443

A home made experimental set-up allows us to measure the thermal conductivity, the thermopower and the thermal diffusivity simultaneously in the temperature range (20-300 K). Therefore the specific heat ... [more ▼]

A home made experimental set-up allows us to measure the thermal conductivity, the thermopower and the thermal diffusivity simultaneously in the temperature range (20-300 K). Therefore the specific heat can be deduced. The role of a radiation shield is shown to be relevant. Tests of the system are made on a 99.9% pure Cu sample and two polycrystalline cuprate ceramics for illustration. Without any complicated optimisation, the technique indicates much promise already due to its efficiency and rapidity. [less ▲]

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See detailTwo peak effect in GMR : a chemical effect ?
Vertruyen, Bénédicte ULg; Rulmont, André ULg; Dorbolo, Stéphane ULg et al

in Materials Research Society Symposium Proceedings (2000), 602

We show that the synthesis conditions have a dramatic influence on the resistivity behavior of calcium and sodium doped LaMnO3. Several samples prepared by lowtemperature techniques exhibit a double ... [more ▼]

We show that the synthesis conditions have a dramatic influence on the resistivity behavior of calcium and sodium doped LaMnO3. Several samples prepared by lowtemperature techniques exhibit a double-peaked curve of resistance versus temperature. The model of spin-polarized intergranular tunneling provides a good approach to discuss our experimental results. Grain size and crystallinity are proved to be essential parameters, which are strongly influenced by the preparation process (e.g. the precursors nature and the thermal treatment). [less ▲]

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See detailEffect of synthesis process and substrate on electrical and thermal transport properties of Bi-2212
Dorbolo, Stéphane ULg; Ausloos, Marcel ULg; Bougrine, Hassan ULg et al

in Journal of Superconductivity (1999), 12(5), 623-629

Resistivity, thermoelectric power, and thermal conductivity have been measured for a Bi-2212 system synthesized from a glassy precursor, either with a commercially Al2O3 substrate or with a homemade ... [more ▼]

Resistivity, thermoelectric power, and thermal conductivity have been measured for a Bi-2212 system synthesized from a glassy precursor, either with a commercially Al2O3 substrate or with a homemade BaZrO3 substrate. Those measurements show that the BaZrO3 substrate gives better superconducting properties to the Bi-2212 than the Al2O3 substrate. The effect of (1.0 T) weak magnetic field has been searched for. The thermal magnetoconductivity and the contributions of the magnetic field to the thermoelectrical power are studied and compared through fine measurements. An electronic contribution seems to appear already well above the critical temperature and to exist up to 200 degrees K. The onset temperature is thus deduced. [less ▲]

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See detailAnomalous temperature behavior of the resistivity in lightly doped manganites around a metal-insulator phase transition
Sergeenkov, S.; Ausloos, Marcel ULg; Bougrine, Hassan ULg et al

in JETP Letters (1999), 70(7), 481-487

An unusual temperature and concentration behavior of the resistivity ρ(T,x) in La0.7Ca0.3Mn1-xCuxO3 is observed at slight Cu doping (0 ≤x≤ 0.05). Namely, the introduction of copper results in a splitting ... [more ▼]

An unusual temperature and concentration behavior of the resistivity ρ(T,x) in La0.7Ca0.3Mn1-xCuxO3 is observed at slight Cu doping (0 ≤x≤ 0.05). Namely, the introduction of copper results in a splitting of the resistivity maximum around the metal-insulator transition temperature T0(x) into two differently evolving peaks. Unlike the original Cufree maximum, which steadily increases with doping, the second (satellite) peak remains virtually unchanged for x<xc, increases for x≥xc, and finally disappears at xm ≃ 2xc, with xc ≃ 0.03. The observed phenomenon is thought to arise from a competition between substitution-induced strengthening of the potential barriers (which hinder the charge hopping between neighboring Mn sites) and weakening of the kinetic energy of the carriers. The data are well fitted by assuming a nonthermal tunneling conductivity theory with randomly distributed hopping sites. © 1999 American Institute of Physics. [less ▲]

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See detailA sharp decrease of resistivity in La0.7Ca0.3Mn0.96Cu0.04O3: Evidence for Cu-assisted coherent tunneling of spin polarons
Sergeenkov, S. A.; Bougrine, Hassan ULg; Ausloos, Marcel ULg et al

in JETP Letters (1999), 69(11), 858-862

Nearly a 50% decrease of the resistivity rho(T,x) is observed upon just 4% Cu doping at the Mn site of La2/3Ca1/3Mn1-xCuxO3. When the observed phenomenon is attributed to a decrease of the spin-polaron ... [more ▼]

Nearly a 50% decrease of the resistivity rho(T,x) is observed upon just 4% Cu doping at the Mn site of La2/3Ca1/3Mn1-xCuxO3. When the observed phenomenon is attributed to a decrease of the spin-polaron energy E-sigma(x) below T-C(x), all of the data are found to be well fitted by the nonthermal coherent tunneling expression rho(T,x)=rho(0)e(-gamma M2(T,x)), assuming that the magnetization in the ferromagnetic state is given by the expression M(T,x)=M-R(x)+M-0(x)tanh{T-[root(C)(x)/T](2)-1}. The best fits through all the data points suggest M-0(x)similar or equal to root 1-xM(0)(0), M-R(x)similar or equal to x root M-0(0), and E-sigma(x)similar or equal to E-sigma(0)(1-x)(4) for the explicit x dependence of the Cu-induced modifications of the Mn-spin-dominated zero-temperature spontaneous magnetization, residual paramagnetic contribution, and spin-polaron tunneling energy, respectively, with E-sigma(0)=0.12 eV. (C) 1999 American Institute of Physics. [S0021-3640(99)00811-7]. [less ▲]

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See detailNegative magnetoresistance in mixed-valence La0.6Y0.1Ca0.3MnO3: Evidence for charge localization governed by the Curie-Weiss law
Sergeenkov, S.; Bougrine, Hassan ULg; Ausloos, Marcel ULg et al

in JETP Letters (1999), 70(2), 141-146

The colossal negative magnetoresistance Delta rho observed in La0.6Y0.1Ca0.3MnO3 at B=1 T shows an unusual, nearly perfect symmetry (around the peak temperature T-0=160 K), suggestive of a Curie-Weiss ... [more ▼]

The colossal negative magnetoresistance Delta rho observed in La0.6Y0.1Ca0.3MnO3 at B=1 T shows an unusual, nearly perfect symmetry (around the peak temperature T-0=160 K), suggestive of a Curie-Weiss-dominated transport mechanism in this material both above and below the field-dependent Curie temperature T(C)equivalent to T-0. Attributing this symmetry to strong magnetic fluctuations below T-C (which are triggered by the Y substitution and cause a "bootstrap" destruction of the ferromagnetic phase), the data are interpreted in terms of the nonthermal spin hopping and magnetization-dependent charge carrier localization scenario leading to Delta rho=-rho(s)(1-e(-gamma M2)), with the magnetization M(T,B)=CB/\ T-T-C(B)\(nu). The separate fits through all the data points above and below T-C yield C(+)similar or equal to 2C(-) and nu(+)similar or equal to nu(-)similar or equal to 1, in agreement with the predictions of the Landau mean-field theory. (C) 1999 American Institute of Physics. [S0021-3640(99)01314-6]. [less ▲]

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See detailComment on "Observation of vortex-lattice melting in YBa2Cu3O7-delta by Seebeck-effect measurements"
Ausloos, Marcel ULg; Bougrine, Hassan ULg; Houssa, M. et al

in Physical Review. B : Condensed Matter (1999), 59(1), 671-673

The findings of Ghamlouch et al. [Phys. Rev. B 54, 9070 (1996)] on the jump in the thermoelectric power of high-T-c superconductors below the critical temperature in the presence of large magnetic fields ... [more ▼]

The findings of Ghamlouch et al. [Phys. Rev. B 54, 9070 (1996)] on the jump in the thermoelectric power of high-T-c superconductors below the critical temperature in the presence of large magnetic fields are discussed. The complicated interplay between the vortex lattice thermodynamic transitions and the transport property percolation transitions raises questions on their similarities, differences, and relationships with respect to the (B,T) phase diagram features and the classical Kosterlitz-Thouless transition. A few comments pertain to the experimental details and others on the relevant role of thermomagnetic transport properties. [S0163-1829(99)04102-8]. [less ▲]

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See detailEstimation of the charge carrier localization length from Gaussian fluctuations in the magneto-thermopower of La0.6Y0.1Ca0.3MnO3
Sergeenkov, S.; Bougrine, Hassan ULg; Ausloos, Marcel ULg et al

in Physical Review. B : Condensed Matter (1999), 60(17), 12322-12328

The magneto-thermoelectric power (TEP) Delta S(T,H) of perovskite-type manganese oxide La0.6Y0.1Ca0.3MnO3 is found to exhibit a sharp peak at some temperature T*=170 K. By approximating the true shape of ... [more ▼]

The magneto-thermoelectric power (TEP) Delta S(T,H) of perovskite-type manganese oxide La0.6Y0.1Ca0.3MnO3 is found to exhibit a sharp peak at some temperature T*=170 K. By approximating the true shape of the measured magneto-TEP in the vicinity of T* by a linear triangle of the form Delta S(T,H) similar or equal to S-p(H)+/-B+/-(H)(T* - T), we observe that B-(H)similar or equal to 2B(+)(H). We adopt the electron localization scenario and introduce a Ginzburg-Landau (GL)-type theory which incorporates the two concurrent phase transitions, viz., the paramagnetic-ferromagnetic transition at the Curie point T-C and the "metal-insulator'' (M-I) transition at T-MI. The latter is characterized by the divergence of the field-dependent charge carrier localization length xi(T,H) at some characteristic field H-o. Calculating the average and fluctuation contributions to the total magnetization and the transport entropy related magneto-TEP Delta S(T,H) within the GL theory, we obtain a simple relationship between T* and the above two critical temperatures (T-C and T-MI). The observed slope ratio B-(H)/B+(H) is found to be governed by the competition between the electron-spin exchange JS and the induced magnetic energy MsHo. The comparison of our data with the model predictions produce T-C = 195 K, JS = 40 meV, M-o = 0.4M(s), and xi(o) = 5 Angstrom for the estimates of the Curie temperature, the exchange coupling constant, the critical magnetization, and the localization length, respectively. The magneto-TEP data obtained by other authors are discussed and Found to be consistent with the model predictions as well. [[S0163-1829(99)00734-1]. [less ▲]

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See detailElectronic contribution to the thermal diffusivity: DyBa2Cu3O7-y and Y0.9Ca0.1Ba2Cu3O7-z
Dorbolo, Stéphane ULg; Bougrine, Hassan ULg; Ausloos, Marcel ULg

in International Journal of Modern Physics B : Condensed Matter Physics, Statistical Physics, Applied Physics (1998), 12(29-31), 3087-3090

The electronic contribution to the specific heat and the thermal conductivity of high-T-c superconductors is calculated with a three-dimensional band structure including saddle points and a Lawrence ... [more ▼]

The electronic contribution to the specific heat and the thermal conductivity of high-T-c superconductors is calculated with a three-dimensional band structure including saddle points and a Lawrence-Doniach coupling between the CuO2 planes. The electronic thermal diffusivity is deduced for s- and d-wave symmetry of the order parameter. Data on DyBa2Cu3O7-y and Y0.9Ca0.1Ba2Cu3O7-z and theory are in good agreement on the change of the slope near T-c. [less ▲]

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See detailAC susceptibility data on Dy2O3 seeded randomly oriented Dy-123 mono domains melt-textured superconductor
Vanderbemden, Philippe ULg; Bougrine, Hassan ULg; Ausloos, Marcel ULg et al

in Materials Science & Engineering : B (1998), 53(1-2), 198-202

Dy-123 superconducting ceramics have been grows using small Dy2O3 single-crystals as seeds. Randomly oriented large mono-domains have been observed in the vicinity of the seeding single crystal. These ... [more ▼]

Dy-123 superconducting ceramics have been grows using small Dy2O3 single-crystals as seeds. Randomly oriented large mono-domains have been observed in the vicinity of the seeding single crystal. These domains are one order of magnitude greater in volume than the seed. The AC susceptibility versus temperature curves have been measured in a polycrystalline cubic sample for different orientations of the magnetic field with respect to the sample and for amplitudes up to 20 G. Three measuring coils, each parallel to one side of the sample, were used to investigate the anisotropy of the properties. Electrical resistance versus temperature and flux profiles at 77 K were also explored. The results show good grain connectivity. A non negligible part of the magnetic shielding is due to currents flowing inside the grains. (C) 1998 Elsevier Science S.A. All rights reserved. [less ▲]

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See detailDistribution of vortex lattice melting temperatures in mixed state diagram of Bi2212 tapes
Pekala, M.; Bougrine, Hassan ULg; Gadomski, W. et al

in Physica C (1998), 303(3-4), 169-176

The electrical resistivity in the mixed state of Bi2212 tape superconductors can be accurately reconstructed for values below approximately a half of the normal state value of resistivity, assuming a ... [more ▼]

The electrical resistivity in the mixed state of Bi2212 tape superconductors can be accurately reconstructed for values below approximately a half of the normal state value of resistivity, assuming a Gaussian distribution for the vortex lattice melting temperatures. The magnetic field dependences of the distribution width and of the dB(c2)/dT parameter were calculated. Moreover the vortex liquid viscosity coefficient was determined between the vortex lattice melting temperature and T-c at various magnetic fields. It is pointed out that the vortex lattice melting transition should not be confused with the irreversibility line of magnetic studies nor with the percolation temperature line for electrical resistivity. (C) 1998 Elsevier Science B,V. All rights reserved. [less ▲]

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See detailTransport properties of HgBaCaCuO(1223) polycrystalline superconductors
Bougrine, Hassan ULg; Houssa, M.; Cloots, Rudi ULg et al

in Superconductor Science & Technology (1998), 11(1), 128-132

We report on the temperature (20-300 K) dependence of the resistivity, thermopower and thermal conductivity measurements of HgBaCaCuO(1223) polycrystalline superconductors with nominal composition Hg1 ... [more ▼]

We report on the temperature (20-300 K) dependence of the resistivity, thermopower and thermal conductivity measurements of HgBaCaCuO(1223) polycrystalline superconductors with nominal composition Hg1.4Ba2Ca2CU3O8+delta. We present some discussion of the precision and the originality of the measurement methods which are especially used to measure the electrical resistivity and simultaneously the thermopower and the thermal conductivity as a function of temperature. The superconductivity fluctuation contributions to the transport properties of the materials are calculated and compared. The results are related to the 2D anisotropy of the crystallographic structure. [less ▲]

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See detailThe effect of BaZrO3 addition on transport properties of Dy-based 123-211 composite materials: electrical resistivity, thermal conductivity and thermoelectric power
Bougrine, Hassan ULg; Ausloos, Marcel ULg; Pekala, M. et al

in Superconductor Science & Technology (1998), 11(8), 803-809

Composite samples made of 123-211 DyBaCuO-based systems with 1, 4, 10 and 15% in weight BaZrO3 additions have been synthesized. Their electrical resistivity, thermal conductivity and thermoelectric power ... [more ▼]

Composite samples made of 123-211 DyBaCuO-based systems with 1, 4, 10 and 15% in weight BaZrO3 additions have been synthesized. Their electrical resistivity, thermal conductivity and thermoelectric power have been measured. The electrical resistivity has also been measured in a magnetic field less than 1 T. The data show that BaZrO3 addition has a non-trivial effect: beside mildly reducing the critical temperature of the superconductor, it increases the scattering at small concentration, and effectively reduces weak link features in the electrical property, but increases the thermal conductivity. The field influence on T-c is shown to be T-c(O)- T-c(B) approximate to B-1/2. [less ▲]

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See detailNote on the measurement of the thermal conductivity and the double peak structure in high-Tc superconductors
Bougrine, Hassan ULg; Pekala, M.

in Superconductor Science & Technology (1997), 10(8), 621-623

We show that low-temperature measurements of the thermal conductivity of high-T-c superconductors can sometimes reveal a double peak structure depending on the experimental set-up used.

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See detailField percolation and high current density in 80/20 DyBa2Cu3O7-x/Dy2BaCuO5 bulk magnetically textured composite ceramics
Cloots, Rudi ULg; Dang, An; Vanderbemden, Philippe ULg et al

in Zeitschrift Fur Physik B-Condensed Matter (1996), 100(4), 551-555

We measured the AC susceptibility of magnetically textured (123) 80%/211(20%) DyBaCuO composite in a special set-up in order to enhance the intergrain contribution. The synthesis process led to very clean ... [more ▼]

We measured the AC susceptibility of magnetically textured (123) 80%/211(20%) DyBaCuO composite in a special set-up in order to enhance the intergrain contribution. The synthesis process led to very clean ''weak links'' at grain boundaries. At the percolation threshold bulk shielding paths were such that the intergrain critical current density J(c) was above 10(5) A/cm(2). The field dependence of J(c) was understood through an analytical form indicating a distribution of currents similar to the law of clusters at fracture/percolation thresholds. [less ▲]

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See detailMagnetic alignment in 2212 Bi-based superconducting system .1. Magnetic orientation of Bi2Sr2Ca1-x(RE)(x)Cu2O8-y [(RE)=Gd, Dy, Ho, Er] powder dispersed in epoxy resin at room temperature
Stassen, S.; Cloots, Rudi ULg; Vanderbemden, Philippe ULg et al

in Journal of Materials Research (1996), 11(5), 1082-1085

The magnetic anisotropy of rare-earth substituted 2212 materials (Bi(2)Sr(2)Ca(0.8)RE(0.2)Cu(2)O(x) with RE = Gd, Dy, Ho, Er) is put into evidence. Superconducting powder dispersed in epoxy resin is ... [more ▼]

The magnetic anisotropy of rare-earth substituted 2212 materials (Bi(2)Sr(2)Ca(0.8)RE(0.2)Cu(2)O(x) with RE = Gd, Dy, Ho, Er) is put into evidence. Superconducting powder dispersed in epoxy resin is oriented under an external magnetic field (4 T) in a direction that depends on the nature of the rare-earth used in the substitution. Both directions of observation (parallel or perpendicular to the field) were investigated. Splitting of (00l) peaks is neatly observed and discussed. [less ▲]

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