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See detailOn the Influence of Blends on the Potential of Ground-based Transit Surveys
Gillon, Michaël ULg; Magain, Pierre ULg

in Afonso, C.; Weldrake, D.; Henning, T. (Eds.) Transiting Extrapolar Planets Workshop (2007, July 01)

Transit surveys have to observe many stars all at once in order to compensate for the rarity of the searched events. Such surveys, especially the ones observing a deep field of view and/or broadening ... [more ▼]

Transit surveys have to observe many stars all at once in order to compensate for the rarity of the searched events. Such surveys, especially the ones observing a deep field of view and/or broadening their stellar images, have to deal with a relatively high level of crowding. This crowding could lead to a reduction of the number of detectable transits, and the estimation of the potential of such surveys without taking into account the influence of blends could give overoptimistic results. We have developed a code which allows to estimate the extent by which such a survey is affected by the crowding of the field of view. Our results show that the influence of blends is important only for severe levels of crowding and is in general much less crucial than the influence of red noise. [less ▲]

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See detailOn the influence of indenter tip geometry on the identification of material parameters in indentation testing
Guo, Weichao ULg

Doctoral thesis (2010)

The rapid development of structural materials and their successful applications in various sectors of industry have led to increasing demands for assessing their mechanical properties in small volumes. If ... [more ▼]

The rapid development of structural materials and their successful applications in various sectors of industry have led to increasing demands for assessing their mechanical properties in small volumes. If the size dimensions are below micron, it is difficult to perform traditional tensile and compression tests at such small scales. Indentation testing as one of the advanced technologies to characterize the mechanical properties of material has already been widely employed since indentation technology has emerged as a cost-effective, convenient and non-destructive method to solve this problem at micro- and nanoscales. In spite of the advances in indentation testing, the theory and development on indentation testing are still not completely mature. Many factors affect the accuracy and reliability of identified material parameters. For instance, when the material properties are determined utilizing the inverse analysis relying on numerical modelling, the procedures often suffer from a strong material parameter correlation, which leads to a non-uniqueness of the solution or high errors in parameter identification. In order to overcome that problem, an approach is proposed to reduce the material parameter correlation by designing appropriate indenter tip shapes able to sense indentation piling-up or sinking-in occurring in non-linear materials. In the present thesis, the effect of indenter tip geometry on parameter correlation in material parameter identification is investigated. It may be helpful to design indenter tip shapes producing a minimal material parameter correlation, which may help to improve the reliability of material parameter identification procedures based on indentation testing combined with inverse methods. First, a method to assess the effect of indenter tip geometry on the identification of material parameters is proposed, which contains a gradient-based numerical optimization method with sensitivity analysis. The sensitivities of objective function computed by finite difference method and by direct differentiation method are compared. Subsequently, the direct differentiation method is selected to use because it is more reliable, accurate and versatile for computing the sensitivities of the objective function. Second, the residual imprint mappings produced by different indenters are investigated. In common indentation experiments, the imprint data are not available because the indenter tip itself shields that region from access by measurement devices during loading and unloading. However, they include information about sinking-in and piling-up, which may be valuable to reduce the correlation of material parameter. Therefore, the effect of the imprint data on identification of material parameters is investigated. Finally, some strategies for improvement of the identifiability of material parameter are proposed. Indenters with special tip shapes and different loading histories are investigated. The sensitivities of material parameters toward indenter tip geometries are evaluated on the materials with elasto-plastic and elasto-visoplastic constitutive laws. The results of this thesis have shown that first, the correlations of material parameters are related to the geometries of indenter tip shapes. The abilities of different indenters for determining material parameters are significantly different. Second, residual imprint mapping data are proved to be important for identification of material parameters, because they contain the additional information about plastic material behaviour. Third, different loading histories are helpful to evaluate the material parameters of time-dependent materials. Particularly, a holding cycle is necessary to determine the material properties of time-dependent materials. These results may be useful to enable a more reliable material parameter identification. [less ▲]

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See detailOn the influence of misclassified data on results of goodness of fit testing
Magis, David ULg

in Statistical Methodology (2005), 2

In this paper we focus on the chi-square test of goodness of fit, which compares an observed discrete distribution to an expected known one. We show that the results of this test, using the common Pearson ... [more ▼]

In this paper we focus on the chi-square test of goodness of fit, which compares an observed discrete distribution to an expected known one. We show that the results of this test, using the common Pearson statistic, are very sensitive to misclassified observations between two or more categories. We also propose a general rule of thumb for analysing data set stability with respect to such classification errors. Practical analysis of a real example illustrates our purpose. [less ▲]

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See detailOn the influence of the disturbed conditions in the centrifugal concentration of heavy fine particles
Patchejieff, B.; Gaydardzhiev, Stoyan ULg; Stoev, S.

in Ozbayoglu, G. (Ed.) Proceedings of the 8-th IMPS Antalya, Turkey, 16-18 X 2000, 167-170 (2000)

Model investigations were carried out with the aim to improve the method for accelerated gravity separation of heavy fine mineral particles. The effects of feed particle size has been studied with the aim ... [more ▼]

Model investigations were carried out with the aim to improve the method for accelerated gravity separation of heavy fine mineral particles. The effects of feed particle size has been studied with the aim to generate disturbed conditions inside the riffle zones of a bowl-type centrifuge and thus to avoid material packing leading to better separation conditions. [less ▲]

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See detailOn the influence of transuranium dilution in well known U heavy fermion compounds
Wastin, Frank; Zwirner, Stefan; Seret, Alain ULg et al

Poster (1995, September)

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See detailOn the influence of transuranium dilution in well-known U heavy-fermion compounds
Wastin, Frank; Zwirner, Stefan; Seret, Alain ULg et al

in Physica B: Condensed Matter (1996), 223-224

Synthesis and preliminary studies on U1−xNpxPd2Al3 and U1−xNpxRu2Si2 are presented. In all Np compounds measured here, no superconducting transition was found down to 1.4 K. In U1−xNpxPd2Al3 a small ... [more ▼]

Synthesis and preliminary studies on U1−xNpxPd2Al3 and U1−xNpxRu2Si2 are presented. In all Np compounds measured here, no superconducting transition was found down to 1.4 K. In U1−xNpxPd2Al3 a small amount (0.01 less-than-or-equals, slant x less-than-or-equals, slant 0.05) of Np induces an anomaly in the lattice parameters and presents in resistivity measurements a sharp minimum at low temperature. [less ▲]

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See detailOn the integration of the equation of radiative transfer.
Swings, Polydore ULg; Dor, L.

in Astrophysical Journal (1938), 88(4), 516-521

The equation of the radiative transfer has been integrated by a generalization of Spitzer's method, which makes use of Bessel functions.

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See detailOn the intensity distribution in the bands of cometary spectra.
Swings, Polydore ULg; Nicolet, M.

in Astrophysical Journal (1938), 88(2), 173-181

The exceptional intensity distribution of bands of unsymmetrical molecules like CN and CH in a comet spectra can be explained by taking into consideration the following factors: (a) the frequency of ... [more ▼]

The exceptional intensity distribution of bands of unsymmetrical molecules like CN and CH in a comet spectra can be explained by taking into consideration the following factors: (a) the frequency of electronic absorption processes; (b) the distribution in the vibrational levels (ground state) which is a function of the nuclear temperature TI or of the equivalent radiation temperature Tλ; (c) the distribution in the rotational levels corresponding to the nuclear temperature. These factors are different functions of the heliocentric distance r. [less ▲]

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See detailOn the Intercostal Muscle Compensation for Diaphragmatic Paralysis in the Dog
Brichant, Jean-François ULg; De Troyer, A.

in Journal of Physiology (1997), 500((Pt 1)), 245-53

1. Paralysis of the diaphragm in the dog is known to cause a compensatory increase in activation of the inspiratory intercostal muscles (parasternal intercostals, external intercostals, and levator costae ... [more ▼]

1. Paralysis of the diaphragm in the dog is known to cause a compensatory increase in activation of the inspiratory intercostal muscles (parasternal intercostals, external intercostals, and levator costae). The present studies were designed to assess the mechanism(s) of that compensation. 2. Complete, selective diaphragmatic paralysis was induced by injecting local anaesthetic into small silicone cuffs placed around the phrenic nerve roots in the neck. 3. Paralysis produced a decrease in tidal volume and an increase in arterial P(CO2) (P(a,CO2)). The increased hypercapnic drive was a primary determinant of the increased inspiratory intercostal activity. 4. However, paralysis also produced an increased inspiratory cranial displacement of the ribs. When this increased rib displacement was reduced to that seen before paralysis, it appeared that the increase in external intercostal and levator costae inspiratory activity was commonly greater than anticipated on the basis of the increased P(a,CO2). 5. Diaphragmatic paralysis after bilateral vagotomy also elicited disproportionate increases in inspiratory intercostal activity, thus indicating that these increases are not caused by vagal afferent inputs. 6. These observations are consistent with the idea that the intercostal muscle compensation for diaphragmatic paralysis is, in part, due to the release of an inhibition originating from the contracting diaphragm. This inhibition might arise in the diaphragmatic tendon organs. [less ▲]

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See detailOn the interpretation of serial laboratory measurements in acute myocardial infarction.
Albert, Adelin ULg; Harris, E. K.; CHAPELLE, Jean-Paul ULg et al

in Clinical Chemistry (1984), 30(1), 69-76

Serial laboratory determinations are now routinely performed on patients admitted to intensive-care units. Adequate interpretation of such cumulative information for clinical decision-making purposes is a ... [more ▼]

Serial laboratory determinations are now routinely performed on patients admitted to intensive-care units. Adequate interpretation of such cumulative information for clinical decision-making purposes is a challenging problem. We describe a statistical method for predicting--sequentially as the data become available--the patient's outcome, death or survival. Thus, the method goes beyond previously reported techniques that base such prediction on only a single multivariate observation. The method has been applied to daily measurements of serum urea and lactate dehydrogenase, performed during one week on patients hospitalized in the coronary-care unit with acute myocardial infarction. Two baseline variables were also included in the dynamic risk index so derived: the age of the patient and the number of previous myocardial infarctions recorded on admission. We also discuss the problems of selecting the most-predictive laboratory tests and of determining for each test the amount of past data needed to achieve satisfactory prediction. We distinguish between global evaluation of the dynamic risk index obtained (in terms of specificity and sensitivity) and individual interpretation (in terms of posterior/prior probability ratio) of a given risk score for a particular patient. The approach described may contribute to more effective use of results of repeated laboratory tests on critically ill patients. [less ▲]

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See detailOn the interpretation of the CH cometary spectrum
Arpigny, Claude ULg; Zeippen, C. J.; Klutz, M. et al

in Diversity and Similarity of Comets (1987)

A procedure to compute cometary spectra taking into account radiative processes and collisional effects is described. The populations of the rotational levels are determined by solving the statistical ... [more ▼]

A procedure to compute cometary spectra taking into account radiative processes and collisional effects is described. The populations of the rotational levels are determined by solving the statistical equilibrium equations at a certain number of locations within the coma (which can be modelled with n(R), T(R), v(R) laws) and the emerging intensity is then evaluated by integrating the emissions along the line of sight. Such a program was applied to the CH radical. The importance of collisions in exciting the lower rotational levels of CH is confirmed. [less ▲]

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See detailOn the interpretation of the emission lines in stars of early spectral class
Struve, Otto; Swings, Polydore ULg

in Astrophysical Journal (1932), LXXXV(3), 161-184

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See detailOn the interpretation of the emission lines in stars of early spectral class
Struve, Otto; Swings, Polydore ULg

in Astrophysical Journal (1932), 75

The emission-line spectra.-The presence of bright Fe II in the spectra of Be stars suggests that lines of other elements requiring similar conditions of excitation may also be present. A search in the ... [more ▼]

The emission-line spectra.-The presence of bright Fe II in the spectra of Be stars suggests that lines of other elements requiring similar conditions of excitation may also be present. A search in the spectra of several stars yielded definite evidence of the presence of Mg II and Si II; Sc II, Cr II, and Ni II are probably present; forbidden Fe II is uncertain. No lines belonging to Ti II coµld be identified, with certainty. The width of the bright line Mg II 4481 greatly exceeds those of the emission lines of H, and in one star the lines of Fe II are definitely wider than those of H. Attributing the origin of the bright lines to a rotating shell of gas, and neglecting support by radiation pressure, we find that the effective distance of Mg II from the center is about seven times the radius of the star, while that of H is ten times the radius of the star. A rough computation of the density of the shell gives 2.5 x 10-13 gr/cm3. The bright lines of Mg II and of Si II are always weak. He I and Ti II are rarely seen in emission. Classification of bright-line spectra.-The published data on Be and Oe stars were collected and arranged according to the Harvard spectral class as derived from the absorption lines. The character of the emission lines shows a definite progression with spectral class. The degrees of effective excitation of the bright and dark lines are not very different in the Oe's but they differ by more than one spectral class in the Be's. There is relatively little dispersion within any given spectral subdivision. This would indicate, on the rotational hypothesis, that the product of the density of the shell and the dilution factor is approximately constant within a given subdivision, but that it varies as a function of spectral type. A new Be star.-Data are given for the Be star 60 Cygni (α 20h57m7 δ +45°46'), which has variable hydrogen lines. Variations in the spectra of Be stars.-Variations in the hydrogen lines of 31 Pegasi (α 22h16m6 δ +11°42') are described. The Be star 31 o Aquarii (α 21h58m1 δ -2°38') is found to have broad and hazy absorption lines of He I and Mg II, and sharp and narrow lines of Fe II. The latter are probably variable. This star is similar to the Be star Є Capricorni; and the suggestion is advanced that the hazy lines are broadened by rotation, while the narrow lines originate through absorption in the same rotating gaseous shell which is believed to give rise to the bright hydrogen lines and to their narrow central absorptions. The spectrum of 17 Leporis.-This spectrum seems to be related to spectra of the P Cygni type : 17 Leporis has bright Hβ in the normal position, accompanied by a strong absorption line on its violet side. Preliminary measurements of one plate give: Mg II +14 km/sec, Fe II and Ti II -64 km/sec, H -93 km/sec. The rotational hypothesis of the origin of bright lines.-A summary is given in support of the hypothesis that the bright lines originate in a rotating shell or ring of gas, and that the dispersion in line widths is mainly due to the effect of inclination. Objections to the rotational hypothesis are discussed and found not to be of a sufficiently serious nature to outweigh the positive evidence. The rotational hypothesis is adopted as the one which fits the observed facts better than any other theory thus far proposed. [less ▲]

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See detailOn the joint analysis of longitudinal responses and early discontinuation in randomized trials
Vandenhende, François; Lambert, Philippe ULg

in Journal of Biopharmaceutical Statistics (2002), 12

Our focus is on the joint analysis of longitudinal nonnormal responses and early discontinuation in (pre)-clinical trials. Separate models are fitted to the two series (response and discontinuation) to ... [more ▼]

Our focus is on the joint analysis of longitudinal nonnormal responses and early discontinuation in (pre)-clinical trials. Separate models are fitted to the two series (response and discontinuation) to account for covariate and time effects. The serial dependence and the dependence between response and drop-out are also modeled. This is done using particular dependence functions, called copulas. Copulas are used to create a joint distribution with given marginal distributions. Applications are given for the analysis of heart rate/morbidity in toxicology and pain severity/intake of rescue medications in a trial on migraine. Using copulas, the level of dependence between two variables remains invariant to changes in the marginal distribution of either variable. This proves interesting in modeling the association in a longitudinal setting when responses change over time. [less ▲]

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See detailOn the Jovian aurorae: recent observational results from the Hubble Space Telescope
Bonfond, Bertrand ULg

Scientific conference (2013, June 06)

The STIS and ACS instruments on board the Hubble Space Telescope revolutionized our understanding of the aurorae at Jupiter. The high sensibility and high spatial resolution of these UV cameras allowed us ... [more ▼]

The STIS and ACS instruments on board the Hubble Space Telescope revolutionized our understanding of the aurorae at Jupiter. The high sensibility and high spatial resolution of these UV cameras allowed us to realize that these auroral emissions are made of a multitude of sub-components, such as the satellite footprints or the Polar Auroral Filaments. Moreover, these sub-components originate from very different regions in the magnetosphere and arise from totally different processes. Here I will review these newly described sub-components with a focus on what we understand, and, more interestingly, on what we still don't understand about them. [less ▲]

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See detailOn the large deformation of axisymmetrique bodies: experimental and numerical studies.
Belkhiri, Laid; Charlier, Robert ULg; Detraux, J. M.

in Proceedings of the Int. Conf. on Numerical Methods in Engineering (1985, January)

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See detailOn the Light Curve of HD 27563
Manfroid, Jean ULg

in Information Bulletin on Variable Stars (1989), 3297

Not Available

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See detailOn the line parameters for the X 1sigma+g (1–0) infrared quadrupolar transitions of 14N2
Goldman, Aaron; Tipping, R.H.; Ma, Q. et al

in Journal of Quantitative Spectroscopy & Radiative Transfer (2007), 103

Re-examination of the 14N2 X 1sigma+g (1–0) line parameters in the HITRAN database showed that the vibration–rotation interaction effect on the line intensities has been neglected, and that the halfwidths ... [more ▼]

Re-examination of the 14N2 X 1sigma+g (1–0) line parameters in the HITRAN database showed that the vibration–rotation interaction effect on the line intensities has been neglected, and that the halfwidths are not compatible with experimental and theoretical studies. New line parameters have been generated, which improve the consistency and accuracy in individual N2 line retrievals from atmospheric spectra. Unresolved line shape issues require further studies. [less ▲]

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