Showing papers by "Eindhoven University of Technology published in 1974"
TL;DR: In this paper, it was shown that the classical theory of gravity driven waves on the surface of a non-viscous liquid can be derived from a set of canonical equations.
Abstract: It is shown that the classical theory of gravity driven waves on the surface of a non-viscous liquid can be derived from a set of canonical equations. Various approximate equations then can be found by introducing suitable approximations to the kinetic and potential energy functionals. The stability of these approximate equations then can be insured beforehand by using positive definite approximate energy functionals. For fairly long, fairly low waves a stable equation of Boussinesq type is derived in this way. This equation is also valid for waves which are not approximately simple.
134 citations
TL;DR: The diameter of craters formed by a vacuum discharge on a copper cathode was determined for single and multiple discharges in the current range of 4-230 A. The most probable current density in the cathode plane is a function of the current and is in the order of 108 A/cm2 as mentioned in this paper.
Abstract: The diameter of craters formed by a vacuum discharge on a copper cathode was determined for single and multiple discharges in the current range of 4-230 A. For a fixed current the crater diameter has values according a lognormal distribution solely determined by the current. Current chopping is characterized by the, forming of craters having one specific diameter (3,6 ?m). After splitting of a discharge the current is on the average equally divided over the partial discharges. The surface geometry influences the movement of the metal vapour discharge over the cathode, it does not affect the distribution of cratersizes. The most probable current density in the cathode plane is a function of the current and is in the order of 108 A/cm2.
127 citations
TL;DR: In this paper, a description is given of five tests based on respectively: (1) the behavior of the error function, (2) the whiteness of the residuals (correlation function), (3) the statistical independency of loss functions, (4) the behaviour of the determinant, and (5) the pole-zero cancellation effect.
99 citations
TL;DR: Graft copolymers prepared by Friedel-Crafts alkylation of the aromatic rings in polystyrene (PS) with the olefinic groups in low density polyethylene (LDPE) are found to be emulsifiers in mechanical blends of PS and LDPE Moreover, this copolymer acts as an adhesive between the two homopolymers.
93 citations
TL;DR: In this paper, a monolayer and intercalation model has been used for the preparation and operation of active catalysts in continuous flow conditions at atmospheric pressure and 400 °C.
80 citations
TL;DR: In this article, the critical surface tension (CST) of borosilicate and soda-lime soft glasss was measured by measuring critical surface tensions (Cst) of the glasses and taking scanning electron micrographs (SEM) before and after various treatments: etching with hydrogen chloride gas, silanization, impregnation with surface active agents, and combinations of these.
70 citations
TL;DR: In this paper, it is shown that the phenomenon of frost having is related to anomalous properties of the adsorbed water layer, situated between the ice and the solid wall, due to the wall influence which is directly manifested in the frost heaving.
68 citations
TL;DR: The internal friction of metaphosphate glasses was measured at 0.5 Hz and 2 kHz as discussed by the authors, and dielectric losses were also measured from 40 to 160°C, at frequencies of 300, 3 000 and 30 000 Hz.
Abstract: The internal friction of LiNa, LiK, LiCs, LiAg, NaCs and NaAg metaphosphate glasses was measured at 0.5 Hz and 2 kHz. The dielectric losses were also measured from 40 to 160°C, at frequencies of 300, 3 000 and 30 000 Hz. The densities of the glasses were determined and the molar volume of oxygen was calculated. In general, the mixed alkali behaviour of metaphosphate glasses is very similar to the mixed alkali behaviour of silicate glasses. Silver behaves in this respect like an alkali ion with approximately the same size as a sodium ion.
46 citations
TL;DR: In this paper, the two internal friction peaks in (1−X) Na2P2O6· X Al2O3 glasses showed a pronounced dependence on the water content and the mechanism for this peak was concluded to consist of the cooperative movement of a sodium ion and a neighboring proton.
Abstract: The two internal friction peaks in (1−X) Na2P2O6· X Al2O3 glasses showed a pronounced dependence on the water content. With increasing water content, the alkali peak became 10–20% smaller and a slight increase in the activation energy was indicated. Similarly, the second peak became 2–4 times larger and shifted to lower temperatures. From the close correlation between the magnitude of the second peak and the water content, the mechanism for this peak was concluded to consist of the cooperative movement of a sodium ion and a neighboring proton. Comparison of aluminophosphate and alkali silicate glasses showed that the internal friction peaks have a similar dependence upon the water content in both types of glasses. It is concluded that the water content of a glass should be closely controlled when the effect of other compositional changes on the internal friction is being studied.
43 citations
TL;DR: Application of apolar glass capillary columns to steroid analysis by gas chromatography is described, where isolated urinary steroids were separated in the gas phase as their methoxime trimethylsilyl derivatives and total urinary steroid profiles are shown.
40 citations
TL;DR: In this paper, microhardness measurements were carried out on single-crystalline manganese aluminates having compositions ranging from Mn1.83Al 1.17O4 to Mn0.91Al 2.03O4.
Abstract: Vickers microhardness measurements were carried out on single-crystalline manganese aluminates having compositions ranging from Mn1.83Al1.17O4 to Mn0.91Al2.06□0.03O4. Hardness increases with increasing alumina content, but the hyperstoichiometric composition shows a decline of hardness probably due to structural vacancies. In Mn1.83Al1.17O4 the crack pattern round indentations is independent of relative indenter orientation and can be accounted for by the presence of a {110} glide system. Apparent hardness anisotropy is related to the position of these glide planes in the surface. In all other harder specimens of this series, other glide systems also become operative during indentation. The occurrence of a pre-precipitation phase after the annealing of specimens is revealed by an increase in hardness, followed by a decline which is due to over-ageing.
TL;DR: In this article, the anodic behavior of iridium in 0.5 M H 2 SO 4 was investigated by cyclic voltammetry and ellipsometry and the results were interpreted by assuming a pit model for the oxidation process.
TL;DR: The phase diagram of the MoFe system between 800 and 1300 °C has been determined using diffusion couples consisting of the pure metals or their alloys in this article.
Abstract: The phase diagram of the MoFe system between 800 and 1300 °C has been determined using diffusion couples consisting of the pure metals or their alloys. The boundary concentrations were measured with an electron probe microanalyser. The μ-(Fe7Mo6) phase has a homogeneity range from 57 to 61.5 at.% Fe; above 1250 °C the Fe-rich boundary shifts towards the Mo-rich side. The R-phase is stable above 1200 °C. Its Fe-rich boundary lies at 65 at.% Fe and is vertical, but the Mo-rich one shifts from 65 at.% Fe at 1200 °C to 62 at.% Fe at 1300 °C. The σ-phase is stable above about 1235 °C and contains about 45 at.% Fe. α-Fe can dissolve 17.9 at.% Mo and Mo 8 at.% Fe at 1300 °C.
TL;DR: Several series of glasses with the general formula x R 2 O · (1 − x )R′ O · P 2 O 5 were prepared and the dielectric loss and internal friction data were taken.
Abstract: Several series of glasses with the general formula x R 2 O · (1 − x )R′ O · P 2 O 5 were prepared and the dielectric loss and internal friction data were taken. The dielectric losses of alkali metaphosphate glasses are greatly reduced by the substitution of alkaline-earth oxide for alkali oxide. Some of the investigated series show a weak minimum in the dielectric loss. The internal friction measurements reveal a high temperature peak, in addition to the single alkali peak and the intermediate temperature peak commonly observed in phosphate glasses. The origin of this high temperature peak is discussed.
TL;DR: In this article, internal friction and dielectric losses of NaK metaphosphate glasses have been investigated and a single alkali and a mixed alkali internal friction peak were observed.
Abstract: The internal friction and the dielectric losses of NaK metaphosphate glasses have been investigated. A single alkali and a mixed alkali internal friction peak were observed. The single alkali peak shifted to higher temperatures with increasing concentration of the second alkali and eventually disappeared. The activation energy of this peak increased with the alkali mixing ratio. As in silicate and borate glasses, the single alkali peak correlates closely with the dielectric loss. The mixed peak showed a dramatic increase in size with the addition of the second alkali, but the activation energy was practically independent of the alkali mixing ratio. The large reduction in height of the mixed peak, observed on annealing, is discussed together with the influence of water.
TL;DR: In this article, it is shown that the conversion from material to local coordinates in continuum mechanics can be considered as a restricted canonical transformation, and that the longitudinal motion of an elastic bar is discussed.
Abstract: It is shown that the conversion from material to local coordinates in continuum mechanics can be considered as a restricted canonical transformation. As a simple example the longitudinal motion of an elastic bar is discussed.
TL;DR: In this paper, the internal friction and dielectric losses of mixed metaphosphate glasses are interpreted on the basis of explanation proposed for the mixed alkali effect, and it is found that the magnitude of the mixed peak correlates better with size differences than with mass differences.
Abstract: The internal friction and dielectric losses of mixed LiNa, LiK, LiCs, LiAg, NaK, NaCs and NaAg metaphosphate glasses are interpreted on the basis of explanation proposed for the mixed alkali effect. It was found that the magnitude of the mixed peak correlates better with size differences than with mass differences. The intermediate temperature peak is treated as a mixed proton-alkali peak. The large mechanical loss peak, appearing when the alkalis are mixed, was attributed to a coupled movement of dissimilar alkali ions and an explanation of the nature of this coupling is proposed. From this model it is predicted that mixed peaks can occur in any electrically insulating material containing dissimilar charge carriers.
TL;DR: In this article, a system consisting of two high-resolution capillary columns of different polarity placed in series is described, which enables the selective transfer of one or more peaks eluted from the first column on to the second column without trapping.
TL;DR: The coulometric and ellipsometric measurements were carried out in 0.5 M H2SO4 to determine the amount and the nature of the oxygen coverage on Ir electrodes in the anodic potential region up to 1400 mV vs. RHE.
TL;DR: In this article, the authors measured noise on InSb, GaAs and GaP homogeneous rectangular single crystals and found that the noise is inversely proportional to the total number of mobile charge carriers.
TL;DR: The phase diagram of the MoCo system between 800 and 1300°C has been investigated by microscopy, X-ray diffraction and electron-probe micro-analysis, using diffusion couples consisting of the pure metals or their alloys as discussed by the authors.
Abstract: The phase diagram of the MoCo system between 800 and 1300°C has been investigated by microscopy, X-ray diffraction and electron-probe micro-analysis, using diffusion couples consisting of the pure metals or their alloys. The μ (Mo 6 Co 7 ) phase has a constant homogeneity range of 7 at.% (51.5–58.5 at.% Co). The θ phase (discovered by Quinn and Hume-Rothery 2 ) is stable between 1018 and 1200°C. Its Mo-rich boundary is found at 81 at.% Co. The Co-rich boundary shifts from 83 at.% Co at 1050°C to 81 at.% Co at 1200°C. The K phase found up to 1000°C has a homogeneity range of 75–76.5 at.% Co. The σ phase is found at and above 1000°C at a composition of about 36 at.% Co. The σ layers were too thin for an accurate determination of the phase boundary concentrations. Co can dissolve 19.5 at.% Mo, and Mo only 1.5 at.% Co at 1300°C.
TL;DR: In this paper, the growth of multilayer oxide (oxide II) on smooth Pt was investigated as a function of cd and temperature in 0·5 and 1 M H2SO4.
TL;DR: High sensitivity, an excellent usability for different types of compounds and no loss of resolution in total ion current vs. flame ionization detector chromatograms are shown.
TL;DR: The preparation of glass capillary columns suitable for analyses at the sub-nanogram level is discussed in this article, where several methods of derivative formation are compared and some results obtained with biologically active compounds are presented.
TL;DR: In this article, the room-temperature spin wave spectrum in MnFe 2 O 4 has been investigated by means of inelastic neutron scattering using the time-of-flight technique.
TL;DR: In this article, a computer program is described which aims at optimum extraction of the information in a given chromatographic signal, without requiring any additional specifications of signal characteristics, and the structure of the program is outlined, emphasizing its adaptive mechanisms.
Abstract: A computer program is described which aims at optimum extraction of the information in a given chromatographic signal, without requiring any additional specifications of signal characteristics. The structure of the program is outlined, emphasizing its adaptive mechanisms. The following components are discussed:
TL;DR: In this paper, the electric field in the aperture of offset front-fed paraboloid antennas and open Cassegrainian antennas, excited by an electric dipole or Huygens source in the focus, is compared with the fields of frontfed circularly symmetrical paraboloidal reflector antennas and classical Cassegranian antennas.
Abstract: In this paper the electric field in the aperture of offset front-fed paraboloid antennas and open Cassegrainian antennas, excited by an electric dipole or Huygens source in the focus, is compared with the fields of front-fed circularly symmetrical paraboloid reflector antennas and classical Cassegrainian antennas. The aperture field forms the basis of expressions to calculate the polarization efficiency of all four types of antenna. Computed results are given, showing that offset antennas can compete with front-fed paraboloids if they are excited by an electric dipole; the classical Cassegrainian antenna, however, shows better results. If offset antennas are excited by a Huygens source, the result is very unfavorable compared with the symmetrical antennas which show no cross polarization.
TL;DR: In this paper, the infrared spectra of MnFe 2 O 4 with inversion degrees of 0.05 and 0.2 are reported and it can be concluded that the absorption observed at 335 cm −1 has to be the third fundamental IR active mode.
TL;DR: The sensitivity of the resonance-fluorescence method for the measurement of very low sodium-vapor densities (<1010 atoms/cm3) has been studied in this article, where light from a sodium spectral lamp is sent through a sodium-containing vessel, whose temperature can be varied.
Abstract: The sensitivity of the resonance-fluorescence method for the measurement of very-low sodium-vapor densities (<1010 atoms/cm3) has been studied. Light from a sodium spectral lamp is sent through a sodium-containing vessel, whose temperature can be varied. The vapor density has been measured in the region of 47–146 °C. At 47 °C, the vapor density is about 107 atoms/cm3. The measurements were performed with both a photon-counting device and a lock-in amplifier. The experimental results have been normalized to absolute density data given in the literature. Fitting our points to the equation logN = a + b/T yields the values a = 23.715 and b = −5257.7 K.