Showing papers by "École Polytechnique published in 1976"
TL;DR: In this article, the melting points of small gold particles have been measured using a scanning electron-diffraction technique and the experimental results are quantitatively in good agreement with two phenomenological models.
Abstract: Recently, small particles have been shown to exhibit a melting temperature which depends on the particle size. The various possible experimental methods have been compared and measurements of the melting points of small gold particles have been made using a scanning electron-diffraction technique. This method was applied to particles having diameters down to 20 \AA{}. Consideration of the size distribution over an entire sample makes it necessary to carry out a careful analysis of the experimental results in order to deduce the melting temperature of particles having a well-defined diameter. The experimental results are quantitatively in good agreement with two phenomenological models. The first model describes the equilibrium condition for a system formed by a solid particle, a liquid particle having the same mass, and their saturating vapor phase. The second model assumes the preexistence of a liquid layer surrounding the solid particle and describes the equilibrium of such a system in the presence of the vapor phase. In order to permit a better comparison between both models, a new expression for the thermodynamic equilibrium condition has been derived in the present work. In the case of the first model, the agreement was obtained using only the physical constants of massive gold. In applying the second model, however, one is compelled to assume the existence of a liquid layer having a thickness of about 6 \AA{}.
3,074 citations
TL;DR: The one-dimensional electronic delocalization that results from the solid-state polymerization of diacetylenes produces a dramatic enhancement of the optical nonlinearities of these compounds as discussed by the authors.
Abstract: The one-dimensional electronic delocalization that results from the solid-state polymerization of diacetylenes produces a dramatic enhancement of the optical nonlinearities of these compounds. The third-order susceptibilities of the polymerized crystals reach very high values comparable to those of inorganic semiconductors.
554 citations
145 citations
TL;DR: In this paper, the singular integral equation (1.2) on a closed surface Γ of R3 admits a unique solution q and is variational and coercive in the Hilbert space H − 1 2 (Γ).
135 citations
01 Jan 1976
TL;DR: This paper intends to present the author’s experience in the field of practical implementation of kriging programs, and it will be shown how these concepts together with techniques like punctual, random, or irregular block krigs will lead to the practical production of useful kriged plans, provided the right question has been asked.
Abstract: This paper intends to present the author’s experience in the field of practical implementation of kriging programs. Too many comparisons leading to wrong conclusions have been made by well intentioned people who stick to strict algorithms and brute force method. After having reviewed the basic theory and the program structure it commands, all time consuming points will be examined and solutions proposed in the area of file search, linear system solution and covariance computations. It will then be shown how these concepts together with techniques like punctual, random, or irregular block kriging will lead to the practical production of useful kriging plans, provided the right question has been asked.
117 citations
TL;DR: In this article, the relativistic plane nonlinear waves were investigated: circularly polarized waves and electrostatic plasma oscillations propagating parallel to the magnetic field, relativists Alfven waves, linearly polarized transverse waves propagating in zero magnetic field and the extraordinary mode propagating at an arbitrary angle to magnetic field.
Abstract: Five relativistic plane nonlinear waves were investigated: circularly polarized waves and electrostatic plasma oscillations propagating parallel to the magnetic field, relativistic Alfven waves, linearly polarized transverse waves propagating in zero magnetic field, and the relativistic analog of the extraordinary mode propagating at an arbitrary angle to the magnetic field. When the ions are driven relativistic, they behave like electrons, and the assumption of an 'electron-positron' plasma leads to equations which have the form of a one-dimensional potential well. The solutions indicate that a large-amplitude superluminous wave determines the average plasma properties.
96 citations
TL;DR: In this paper, the same centers are responsible for the recombination in the diode and in pure silicon, that only the recombinations in the space charge region of the junction is spin-dependent and that the effect in this region is very large.
90 citations
TL;DR: A preferential conformation of the endogenous opiate-like pentapeptide Met-Enkephalin in DMSO-d6 solution was proposed from high field 1H NMR experiments at variable temperature and complete analysis of the coupling constants in relation with conformational energy steric maps.
89 citations
TL;DR: In this paper, the authors studied the statistical properties of the total revenues generated by one of the mechanisms with this desirable dominant strategy property, and showed that the expected total revenues increase like √ N.
89 citations
TL;DR: In this paper, the preparation of carbon adsorbents suitable for reversed-phase high-performance liquid chromatography is described, and the effect of the amount of carbon deposited by benzene pyrolysis on thermal carbon blacks on the hardness and specific surface area of the particles obtained is discussed.
85 citations
TL;DR: In this paper, a technique for coating silica particles with a layer of pyrocarbon is described, where the conditions of preparation are important as they determine both the chromatographic performance and the degree of agglomeration of particles during coating.
TL;DR: In this paper, the interface profile of the two-dimensional Ising ferromagnet is obtained for all temperatures in the thermodynamic limit, and the width of the interface depends on its length as (length) 1/2.
Abstract: The interface profile of the two-dimensional Ising ferromagnet is obtained for all temperatures in the thermodynamic limit. The width of the interface depends on its length as (length)1/2.
TL;DR: The potential use of modified carbon blacks as adsorbent for high-performance liquid chromatography is discussed in this paper, where the technique of particle hardening through benzene pyrolysis is described.
TL;DR: In this paper, the authors prove the H-stability property and the existence of the thermodynamic limit of the free energy density of the two-dimensional, one-component classical plasma.
Abstract: We prove theH-stability property and the existence of the thermodynamic limit of the free energy density of the two-dimensional, one-component classical plasma. We give lower and upper bounds on the free energy density in any dimensionv and draw some consequences.
TL;DR: In the Gargamelle neutrino experiment, three unambiguous candidates for the reaction ν μ + e − → νμ e − have been observed corresponding to a cross section for a recoil electron energy within the range 0.06 × 10 −41 E ν (GeV ) cm 2 / electron as discussed by the authors.
TL;DR: In this paper, the infrared dispersion of the third-order susceptibility describing the mixing of visible light beams in transparent dielectric crystals is discussed, where important contributions arise from local field effects and waves created by lower order nonlinearities in noncentrosymmetric crystals.
TL;DR: In this paper, a charmed hadron was observed in the bubble chamber Gargamelle exposed to the CERN neutrino beam, which strongly indicated the existence of a new type of interaction leading to a charged lepton pair correlated with a strange particle.
01 Jan 1976
TL;DR: In this article, it was shown that under realistic conditions, even far from the optimal, resolution is always increased if the cycle number is sufficiently large, and that the potential of recycling a mixture of two closely eluted compounds is excellent.
TL;DR: In this paper, the vibrational relaxation of ortho-para-H 2 in collisions with 4 He has been studied in the interval 300-50 K. At 300 K the ortho H 2 - He and para H 2- He rates are identical within experimental error.
TL;DR: In this article, it was shown that the two-dimensional isotropic ferromagnetic rotator model exhibits a first order phase transition if the interaction decays asr−α with 2<α<4.
Abstract: We show that the two-dimensional isotropic ferromagnetic rotator model exhibits a first order phase transition if the interaction decays asr
−α with 2<α<4
TL;DR: In this article, a new rigorous and simple study of the time-delay formula is presented, where the authors present a simple and rigorous approach to calculate the time delay of a time interval.
Abstract: A new rigorous and simple study of the time-delay formula is presented.
TL;DR: In this paper, it was shown that decaying states without regeneration do not exist for unstable quantum systems, but they are natural for regular stationary processes, which is a direct proof of the Szego-Kolmolgorov-Krein characterization.
Abstract: In a previous publication (Boletin de la Sociedad Matematica Mexicana 1975) it was established that any weakly stationary linearly regular stochastic process is unitarily equivalent to a quantum mechanical momentum evolution. The object of the present note is, as promised in the previous publication, to amplify some of the details concerning the just mentioned interesting connection, giving in particular a direct proof of the Szego-Kolmolgorov-Krein characterization of regular stationary processes. We also show that although the so-called decaying states without regeneration do not exist for unstable quantum systems, they are natural for regular stationary processes.
TL;DR: In this article, Raman scattering and infrared reflectivity results are reported for the 2H and 4H polytypes of PbI2, and two polytypes can be clearly distinguished by their vibrational properties.
Abstract: Raman scattering and infrared reflectivity results are reported for the 2H and 4H polytypes of PbI2. The two polytypes can be clearly distinguished by their vibrational properties. The infrared reflectivity shows a broad reststrahlen band, pointing to the significantly ionic character of this compound.
Cet article presente des mesures de diffusion Raman et de reflectivite infrarouge pour les polytypes 2H et 4H de PbI2. Les deux polytypes se distinguent clairement par leurs proprietes vibratoires. En reflexion infrarouge, une large bande de rayons restants montre le caractere ionique de ce compose.
TL;DR: In this article, strong decay properties for lattice systems with generaln-body interactions were proved for continuous systems with two-body and n-body interaction, where the range of the potentials is finite or infinite.
Abstract: Various strong decay properties are proved for lattice systems with generaln-body interactions, and for continuous systems with two-body andn-body interactions. The range of the potentials is finite or infinite.
TL;DR: In this paper, an analytical equation for the spectral evolution of dye laser emission was derived, which is useful in understanding injection locking, progressive narrowing, enhancement of intracavity absorption and amplification, dual-wavelength dye lasers, broad band shift and coupled cavities.
TL;DR: In this paper, the retention data on carbon adsorbents are proportional to the total surface area of the adsorbent in the column, within the limits of error of measurement of this parameter, except for polyaromatics.
01 Jan 1976
TL;DR: By necessity, all the planning in an open pit mine is done on the basis of estimated values, but it is not these estimated values that are mined, but rather the real values which were unknown at the time of planning.
Abstract: By necessity, all the planning in an open pit mine is done on the basis of estimated values. Since it is not these estimated values that are mined, but rather the real values which were unknown at the time of planning, discrepancies will occur between what was planned and what is achieved.