Showing papers by "Eindhoven University of Technology published in 1981"
TL;DR: Experimental studies on 1/f noise are reviewed with emphasis on experiments that may be decisive in finding the correct theoretical model for this type of noise as discussed by the authors. But the applicability of either theory turns out to be very limited.
Abstract: Experimental studies on 1/f noise are reviewed with emphasis on experiments that may be decisive in finding the correct theoretical model for this type of noise. The experimental results are confronted with two theories: McWhorter's (1959) surface state theory and Clarke and Voss's (1974) theory of local temperature fluctuations. The applicability of either theory turns out to be very limited. The validity of an empirical relation is investigated. Its application to electronic devices proves successful. Experiments show that 1/f noise obeying the empirical relation ( alpha noise) is a fluctuation in the part of the mobility that is due to lattice scattering.
1,057 citations
01 Jan 1981
TL;DR: A submitted manuscript is the author's version of the article upon submission and before peer-review as discussed by the authors, and the final published version features the final layout of the paper including the volume, issue and page numbers.
Abstract: • A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers.
392 citations
01 Jan 1981
263 citations
TL;DR: In this paper, the authors examined the effect of viscous heat dissipation on HPLC columns and concluded that viscous temperature dissipation constitutes an obstacle to obtaining higher speed and efficiency in HPLC by using smaller particles.
Abstract: Temperature effects in HPLC columns due to viscous heat dissipation are examined. For the case when the thermostatted column wall and mobile phase at the column inlet are at the same temperature an explicit solution of the heat transport equation is given. The predicted temperature profile is parabolic at large distances from the column entrance; the magnitude of the effect is proportional to the square of the mobile phase velocity, and is of the order of a few degrees centigrade. At the upper end of the column a relaxation occurs over a length of a few centimers. Experimental results confirm the validity of the predictions made and indicate that the various assumptions and approximations are justified. Plate height curves obtained with two mobile phases with differing viscosities show a much smaller efficiency for the less viscous mobile phase. The curves show an upward curvature at high reduced velocities. Both phenomena can be related to thermal effects. It is concluded that viscous heat dissipation constitutes an obstacle to obtaining higher speed and efficiency in HPLC by the use of smaller particles. Possible remedies, such as the use of smaller bore columns or special thermostatting devices, look troublesome from the experimental point of view.
175 citations
TL;DR: In this paper, the application of a composite material as a magneto-electric transducer has been discussed and the results of the measurements on frequency response, transfer characteristics, internal impedance, temperature dependence and noise are discussed.
Abstract: This article deals with the application of a composite material as a magneto-electric transducer. The composite, which has both magneto-strictive and piezo-electric properties was developed at Philips' Research Laboratories. A transducer consisting of a piece of composite appears to be a suitable replacement for e.g. Hall devices, especially in AC applications. It needs only two electrical contacts and has a flat frequency response from a few Hz up to 650 kHz, where mechanical resonance occurs. Several calculations and experiments were carried out on the transducer and its electronic analogon, as well as on the measuring set-up, which had to produce a calibrated magnetic field. The results of the measurements on frequency response, transfer characteristics, internal impedance, temperature dependence and noise are discussed. The construction of a magnetic field probe using the composite is described and finally some other applications are given.
149 citations
TL;DR: In this article, the origin of droplet-flow and ion-flow is considered and the available data pertinent to this subject is discussed, and it is concluded that ionized mass flow is directly related to the generation of crater structures in the cathode surface.
Abstract: Considerable effort has been devoted to the analysis of mass flows in vacuum arcs during recent years. It is generally agreed that there are three different fluxes which orginate from the cathode; they consist of ions, molten droplets and metal vapour. A critical summary will be given of the available data on these mass flows. The question of the large discrepancies in cathode erosion rate measurements is discussed. Minimum and maximum erosion rates are analyzed and it is shown that these discrepancies can be understood only if the variation of liquid metal erosion with different parameters is taken into account. The origin of droplet-flow and ion-flow is considered and the available data pertinent to this subject is discussed. It is concluded that the origin of ionized mass flow is directly related to the generation of crater structures in the cathode surface. Droplet erosion, on the other hand, is primarily related to cathode spot movement and is a surface heating effect. Finally, a summary is given of a model in which the different observations on cathode flows are explained in a consistent way. The model is supported by a numerical analysis of ion mass production by Joule heating. Close agreement is obtained for around twenty different cathode metals.
142 citations
TL;DR: In this paper, the authors analyzed the beam profile measurements of a supersonic beam source in a cryoexpansion chamber and showed that the centerline intensity I(0)(s−1sr−1) of the source is fully described by the peaking factor κ =π(I(0)/N), with N (s− 1) the flow rate.
Abstract: The centre-line intensity I(0)(s−1sr−1) of a supersonic beam source is fully described by the peaking factor κ=π(I(0)/N), with N (s−1) the flow rate. For a skimmerless source in a cryoexpansion chamber we find κ = 2.07, 1.48, 1.47, 1.20 and 1.17 for Ar, O2, N2, CO2 and CH4, respectively. These results are in fair agreement with numerical solutions of the flow field downstream of the sonic plane. The shielding effect of the skimmer is conveniently described by mapping the perpendicular distribution, which cools geometrically, into a constant virtual source distribution in the nozzle plane. We use a bimodal distribution to analyze the beam profile measurements. For Ar and Kr the radius R1 of the narrow virtual source is given by R1/zref=4.4(Ξ/100)0.28 with zref=0.802Rn, Rn being the nozzle radius, Ξ=3.189((γ−1)/γ) 1 2 n 0 z ref (C 6 /kT 0 ) 1 3 the source parameter, n0 and T0 the number density and the temperature of the reservoir, respectively. These results are in good agreement with a “last collision surface” extension of the thermal conduction model by Habets. For O2 and N2 we find R1/zref=10.1(Ξ/100)0.42 with zref= 0.598Rn. By scaling the “last collision surface” from the Ar and Kr data for the case of diatomics we find fair agreement with a modified thermal conduction model by Klots. The broad virtual source is very important for describing the shielding effect of the skimmer. The radius R2 is in the range 4⩽R1/R2⩽8 and its population consists of 30% ( γ= 5 3 ) to 50% ( γ= 7 5 ) of all particles. For Ξ⩽100 th e loss of intensity is less than 10% if we use the design rules Rs=20Rn for monoatomic and Rs=40Rn for diatomic gases, with Rs the radius of the circular skimmer opening.
123 citations
01 Jan 1981
113 citations
TL;DR: In this article, the deactivation of the catalyst is attributed to the formation of platinum oxide (PtO2), which can be reversed by temporarily replacing the oxygen flow by a nitrogen flow.
113 citations
TL;DR: In this paper, a theoretical treatment of the optimum gas chromatographic conditions for open-tubular columns, operated at vacuum outlet pressures, is presented, where the minimum plate height, the optimum linear gas velocity and the optimum inlet pressure are derived.
108 citations
TL;DR: In this paper, the role of Co and Ni in thiophene hydrodesulfurization was investigated and it was shown that at low concentrations, the promoter function is probably an adequate explanation.
TL;DR: In this paper, the Schulz Flory α has a tendency to increase from C3 to C7, and a corresponding reduction in the ethene yield is observed for high ratios of hydrogen to carbon monoxide.
TL;DR: A review is given of sugar analysis by liquid chromatography using silica columns with focus on column materials and preparation, chemically and physically modified amine columns, octadecyl-and unmodified silica Columns.
01 Jan 1981
TL;DR: It is shown that the flow in chromatography is nearly always laminar in nature and the concepts of specific permeability, chromatographic permeability and column resistance factor are discussed for packed as well as open tubular columns.
Abstract: It is shown that the flow in chromatography is nearly always laminar in nature. Starting from the Darcy equation, expressions are given for the flow rate in both gas and liquid chromatography columns. The concepts of specific permeability, chromatographic permeability and column resistance factor are discussed for packed as well as open tubular columns. The experimental determination of all these factoers is demonstrated. The influence of the shape and pore volume of porous and non-porous supports on the column resistance factor and the chromatographic permeability is discussed.
TL;DR: In this paper, the deactivation due to the formation of PtO2 and the oxidation reaction are chemically coupled, and are explained in the same way as in the oxidation of glucose.
TL;DR: In this article, the electrical resistivity and the Seebeck coefficients of Mn3O4, in the temperature range 1100-1700 K, have been measured under oxygen partial pressures of 1−10−6 atm.
TL;DR: In this paper, it has been shown that in the linear case the relation between the electric field E and the polarization P has the form of a linear relation among E, P, the first derivatives with respect to time of E and P, and the second derivative with respectto time of P.
Abstract: In a previous paper it has been shown by the author that a vectorial internal variable may give rise to dielectric relaxation phenomena and that if such a variable occurs the polarization P may be written in the form P = P (0) + P (1) , where changes in P (0) are reversible processes and changes in P (1) are irreversible. In this paper we introduce a somewhat more general assumption concerning the entropy. This generalization leads to the possibility that both changes in P (0) and in P (1) are irreversible phenomena. In this way a formalism is obtained with two relaxation times for dielectric relaxation. In particular we investigate the linearized form of the theory. It is seen that in the linear case the relation between the electric field E and the polarization P has the form of a linear relation among E , P , the first derivatives with respect to time of E and P , and the second derivative with respect to time of P . Debye's equation for dielectric relaxation in polar liquids and the equation derived by De Groot and Mazur are special cases of the equation which has been obtained in this paper. Analogous results can be derived for magnetic relaxation phenomena. Snoek's equation and the equation obtained by De Groot and Mazur are special cases of the equation for magnetic relaxation which is derived in this paper.
TL;DR: In this article, a model for the volume strain of a two-phase blend which elongates homogeneously in a tensile test apparatus is presented for any homogeneous system which deforms without necking and where one or more deformation mechanisms is present.
Abstract: A model is presented for the volume strain of a two-phase blend which elongates homogeneously in a tensile test apparatus. In the case when only elastic deformation and crazing take place the volume strain against elongation curve can be constructed and calculated from the data of the stress-strain curve alone. When, as well as crazing and elastic deformation, shearing takes place, the data of the stress against elongation curve and the volume strain against elongation curve can be used to calculate the separate contributions of the three deformation mechanisms at any elongation. In principle, the model can be also used for any homogeneous system which deforms without necking and where one or more deformation mechanism is present.
TL;DR: An improvement in the chromatographic separation of sugars and sugar alcohols on cation exchangers with water as eluent is presented in this paper, where an addition of 0.001 M triethylamine to the eluents catalyses the mutarotation of reducing sugars, and results in reduced peak widths.
TL;DR: In this paper, the authors investigated the ternary phase diagram of Ti-Ni-Fe by means of diffusion couple technique and by the investigation of equilibrated alloys.
Abstract: We investigated the 900 °C cross section through the ternary phase diagram Ti-Ni-Fe by means of the diffusion couple technique and by the investigation of equilibrated alloys The course of a number of diffusion paths was established Use was made of optical, microprobe and X-ray analyses Some hitherto unaccountable results mentioned in the literature can now be explained
TL;DR: In this paper, the ESR spectra of nickel- or cobalt-promoted sulfided tungsten- or molybdenum-containing catalysts are measured together with the influence of equilibration at different H2SH2 ratios and CO adsorption.
TL;DR: In this article, the problem of the conversion of mechanical energy into heat is treated, while a general theory of thermoelastic friction in three-dimensional finite bodies is developed.
Abstract: This paper consists of three parts. In the first part, the problem of the conversion of mechanical energy into heat is treated, while in the second a general theory of thermoelastic friction in three-dimensional finite bodies is developed. In the third part, explicit results are obtained for thermoelastic damping in vibrating elastic beams. All investigations are based on the linear theory of thermoelasticity.
TL;DR: All values of n(7, d) will now be presented.
TL;DR: The influence of surfactants on suspensions of monoionic kaolinite (Na + and H + form) was investigated by adsorption, sedimentation, turbidity, electroosmosis, and rheological measurements, at pH = 3.3 and 10.0 as mentioned in this paper.
TL;DR: In this paper, the Thornber-Feynman expression for the nonlinear conductivity of continuum polarons was derived in the framework of the Heisenberg equations of motion, and the electron velocity distribution function was calculated explicitly for every value of the electron-phonon coupling constant, temperature, and electric field strength.
Abstract: The nonlinear response of continuum polarons to a static electric field is investigated. The Thornber-Feynman expression for the nonlinear conductivity (in the case of the Feynman model) is rederived in the framework of the Heisenberg equations of motion. Following the prescription of Thornber, the electron velocity distribution function corresponding to the Thornber-Feynman theory is calculated explicitly for every value of the electron-phonon coupling constant, temperature, and electric field strength. It turns out to be a drifted Maxwellian with an effective electron temperature which is only a function of the lattice temperature and the effective electron-phonon interaction (which is given by the parameters of Feynman's polaron model). For small electron-phonon coupling this conclusion is discussed in the context of solutions of the Boltzmann equation for the distribution function.
TL;DR: In this paper, the authors use ridge regression analysis to overcome the problem of multicollinearity in the development of multi-attribute shopping models and apply it to spatial shopping behavior.
Abstract: Policy decisions regarding retailing facilities essentially involve multiple attributes of shopping centres. If mathematical shopping models are to contribute to these decision processes, their structure should reflect the multiattribute character of retailing planning. Examination of existing models shows that most operational shopping models include only two policy variables. A serious problem in the calibration of the existing multiattribute shopping models is that of multicollinearity arising from the fact that strong linear relationships among policy variables frequently occur in real world situations. This paper points at the technique of ridge regression analysis to overcome the problem of multicollinearity in the development of multiattribute shopping models. The use of ridge regression analysis is illustrated in an application of the multiplicative competitive interaction model to spatial shopping behaviour.
TL;DR: In this paper, a new model of 1/f noise in MOS transistors is presented which is based on the Hooge model and takes into account the high electric field strengths in the channnel.
Abstract: At present there are two theories of 1/f noise in metal‐oxide‐semiconductor (MOS) transistors. One is based on the McWhorter model (number fluctuations), the other on the Hooge model (mobility fluctuations). In both theories the influence of high electric‐field strengths on the mobility of carriers in the channel were left out of consideration. Here a new model of 1/f noise in MOS transistors is presented which is based on the Hooge model and takes into account the high electric‐field strengths in the channnel. The theoretical results agree well with experimental results.
TL;DR: In this paper, the authors considered the Hall plate with four equal finite line contacts, lying symmetrically in respect of two orthogonal axes, and derived analytical expressions for the Hall voltage and the Hall mobility in which the finiteness of the contacts and the magnetic field are taken into account.
Abstract: The circular Hall plate with four equal finite line contacts, lying symmetrically in respect of two orthogonal axes, is considered. Analytical expressions for the Hall voltage and the Hall mobility in which the finiteness of the contacts and the magnetic field are taken into account, are obtained by applying Schwarz-Christoffel transformations. It is shown that the numerical calculations involved can be reduced to those of regular definite integrals. Furthermore, in the case of not too large contacts, a simple approximative formula has been derived for the product μHB of Hall mobility and magnetic induction. It is given in a form directly suited to practical applications.