Showing papers by "Delft University of Technology published in 1979"
TL;DR: A PECULIAR sterol has been found in recent sedimentary environments which was found was identical with the Black Sea sterol and its significance was discussed.
Abstract: A PECULIAR sterol has been found in recent sedimentary environments which we eventually found was identical with the Black Sea sterol. This sterol was first mentioned among the extractable sterols from the Black Sea sapropel layer as the dominant component1. The concentration of this sterol in these rare sediments seemed high enough for us to isolate and purify the object to determine its molecular structure and evaluate its significance. We have isolated and analysed the sterol fractions from the Black Sea sapropel (by techniques to be described elsewhere), but here only elucidate the molecular structure of the Black Sea sterol and discuss its significance.
361 citations
TL;DR: The prosthetic group of glucose dehydrogenase is, like that of methanol dehydrogen enzyme [3-S], a ‘pyrroloquinoline quinone’ (PQQ) and the name ‘quinoproteins’ is proposed for this distinct class of dehydrogenases.
238 citations
TL;DR: In this paper, the authors describe the theory of frictional rolling contact as far as it is significant for the wheel-rail system and give a present day account of the simplified theory and the exact linear and non-linear theory.
Abstract: SUMMARY This paper describes the theory of frictional rolling contact as far as it is significant for the wheel-rail system. It is divided into two parts. The first part, mostly non-mathematical, contains a historical survey from the times of Carter and Fromm (1926) to the present day, in which all aspects of rolling contact theory are discussed. Included are a quantitative account of the results of Hertz theory (Section 3), and a table of the creepage and spin coefficients. The second part gives a present day account of the simplified theory (Section 4), and of the exact linear and non-linear theory (Section 5). The paper closes with some recommendations for future research, of which the most pressing is a thorough investigation of the accuracy of simplified theory.
228 citations
145 citations
TL;DR: In this article, the computer code Duvorol, dealing with the computation of three-dimensional rolling contact with dry friction, is described, which is based on the variational principle of Duvaut and Lions for dry friction.
Abstract: In this paper the computer code Duvorol, dealing with the computation of three-dimensional rolling contact with dry friction, is described. It is based on the variational principle of Duvaut and Lions for dry friction, which leads to an incremental theory. The relevant properties of Duvorol are:
1Generality. All half-space steady-state rolling contact problems with Hertzian normal contact can be treated.
2Reliability. The total tangential force is always found with reasonable accuracy by a standard discretization.
3Speed. On an IBM 370/158 the calculation of a case then takes only several seconds.
144 citations
TL;DR: In this paper, a new method is introduced by which is able to obtain a decoupled absorption spectrum with linewidths independent of the transverse relaxation rate, where spin echoes are created by means of 90-180" pulse sequences, for different intervals t/2 between the 90 and 180" pulses.
128 citations
TL;DR: In this paper, the author presented a series of eight lectures on fatigue crack growth at the Delft University of Technology during the course year 1976-1977 at a Seminar on Fatigue, Fundamental and Applied Aspects, organized by the Lmkoping Institute of Technology.
124 citations
01 Jan 1979
TL;DR: A survey of existing theories and measurements of the rheology of mold suspensions is given in this paper, where the implications of mould rheological properties for the design of reactors are discussed.
Abstract: A survey is given of existing theories and measurements of the rheology of mould suspensions. The Casson equation gives a good description of rheology and the impeller method is very suitable for viscosity measurements. The parameters in the Casson equation can be correlated with morphology and volume fraction. Osmotic pressure has a pronounced effect on viscosity, while the pellet growth form can decrease viscosity significantly. The implications of mould rheology for the design of reactors are discussed.
123 citations
TL;DR: In this article, the initial behavior of a series of monosaccharides in aqueous, alkaline medium has been studied by using u.v. spectroscopy, and the reaction rate constants have been determined for both the formation and the conversion of the enediol anion by using the overall reaction scheme: sugar + -OH α sugar anion α enedi anion → β-elimination intermediates → products.
120 citations
TL;DR: A fast and simple iterative method for the determination of a single real root of a real continuous function based upon linearizing the original function and the regula falsi is applied to this modified function which leads to a very simple algorithm.
Abstract: A fast and simple iterative method is proposed for the determination of a single real root of a real continuous function. The idea is based upon linearizing the original function whereafter the regula falsi is applied to this modified function which leads to a very simple algorithm. The rate of convergence is shown to be quadratic or better.
119 citations
TL;DR: The principal isoprenoid, obtained by the high temperature pyrolysis of kerogens has been identified as prist-1-ene and it is reported that the role of kerogen as a source, or sink, of isoprene moieties is not completely understood.
Abstract: A SERIES of acylic isoprenoid alkanes, of which pristane and phytane are typical, frequently occurs in crude oils, shales, coals, bitumens and so on. It is generally agreed that the primary source of these compounds is the phytyl side chain of chlorophyll1,2 although the mechanisms of its incorporation into sediments and its subsequent diagenesis, are not completely understood. At present, little is known about the role of kerogen as a source, or sink, of isoprenoid moieties and we report here that the principal isoprenoid, obtained by the high temperature (600 °C) pyrolysis of kerogens has been identified as prist-1-ene.
TL;DR: In this paper, perylene was abundant and was the only high molecular weight polycyclic aromatic hydrocarbon present in the Namibian seafloor sediments collected at two sites offshore of southwest Africa.
TL;DR: In this article, the Rayleigh hypothesis in the theory of reflection by a grating is investigated analytically, and conditions are derived under which the hypothesis is rigorously valid.
Abstract: In this paper, the Rayleigh hypothesis in the theory of reflection by a grating is investigated analytically. Conditions are derived under which the Rayleigh hypothesis is rigorously valid. A procedure is presented that enables the validity of the Rayleigh hypothesis to be checked for a grating whose profile can be described by an analytic function. As examples, we consider some grating profiles described by a finite Fourier series. Numerical results are then presented.
TL;DR: In this article, a method for pure absorption spectra from spin echoes with a symmetric envelope amplitude, but with arbitrary phases φ in the centers of the echoes, was presented.
TL;DR: Partial reduction of the isolated prosthetic group of methanol dehydrogenase yields a free radical with the same characteristics as the one contained in the enzyme that is interpreted in terms of an isotropic g-value, hyperfine coupling constants and nuclear spins.
TL;DR: In this article, a mathematical model for suspended sediment transport is described, which enables the investigation of certain effects of river works or geometrical changes, or both, in a river or estuary by morphological computations.
Abstract: A mathematical model for suspended sediment transport is described, which enables the investigation of certain effects of river works or geometrical changes, or both, in a river or estuary by morphological computations. The model is based on the two-dimensional diffusion-convection equation. This equation describes the distribution of the sediment concentrations in a two-dimensional flow field by diffusion and convection. For the local velocities in the vertical the logarithmic distribution is used, while for the sediment diffusion coefficient a new expression is applied. The diffusion-convection equation is solved by an implicit numerical method using a coordinate transformation, while the influence of the diffusion coefficient on the adaptation of the transport in the case of an overcapacity of sediment is presented. A dimensionless graph of the adaptation length of a uniform concentration vertical is given, the application of the model for tidal flow is described and for such conditions a prototype verification and a sensitivity analysis is given. The model is limited to situations with relatively small changes in lateral direction and nongraded bed.
TL;DR: In this paper, the synthesis and characterization of new coordination compounds of Pt(II) and Pd(II), with the nitrogen-donor ligand imidazole (IzH), is described.
TL;DR: In this article, comparative computations have been carried out with the CERC formula and the Bijker formula, the adapted Engelund-Hansen formula, and the adapted (2 methods of adaptation) Ackers-White formula.
TL;DR: From this solution an efficient numerical procedure is derived for synthesis of discrete-interval, binary, periodic signals the Fourier amplitude spectrum of which is optimal in the same sense.
Abstract: A closed-form solution is presented for the discrete-interval, binary, periodic signal the complex Fourier coefficient spectrum of which optimally approximates in the least squares sense a desired complex Fourier coefficient spectrum. From this solution an efficient numerical procedure is derived for synthesis of discrete-interval, binary, periodic signals the Fourier amplitude spectrum of which is optimal in the same sense. Numerical examples show the practical feasibility of the procedure.
TL;DR: In this paper, the substitution of halobenzenes by bromine at 25 °C is catalyzed by Y-type zeolites, partially exchanged with di- and trivalent cations.
TL;DR: In this article, the spectral selectivity of tin dioxide layers has been optimised in an experimental study using Drude's theory, which gives a free electron model which makes it possible to compute the spectral reflectance as a function of electrical properties of a conducting material.
TL;DR: Wax esters (ranging from C32 to C44), very long mid-chain ketones and sterol ethers were isolated from Walvis Bay diatomaceous ooze and identified by glass capillary gas chromatography/mass spectrometry and direct probe high-resolution mass spectrometric as discussed by the authors.
TL;DR: The Rayleigh hypothesis in the theory of scattering by a cylindrical obstacle of arbitrary cross section is investigated analytically in this article, where conditions under which the Rayleigh hypotheses are rigorously valid are derived.
Abstract: The Rayleigh hypothesis in the theory of scattering by a cylindrical obstacle of arbitrary cross section is investigated analytically. The hypothesis asserts that outside and on the obstacle the scattered field may be expanded in terms of outward-going wave functions of the circular cylinder. As such, it is analogous to the assumption made by Lord Rayleigh in his treatment of diffraction by a reflection grating. We show that the validity of the Rayleigh hypothesis is governed by the distribution of singularities in the analytic continuation of the exterior scattered field. Conditions are derived under which the Rayleigh hypothesis is rigorously valid. As examples, the elliptic cylinder and the perturbed circular cylinder are considered in detail.
TL;DR: It is shown that Bayesian probability measures, which are used for feature selection, and are based on distance measures and information measures, are basically of two types, which clarifies some properties of these measures for the two-class problem and for the multiclass problem.
TL;DR: In this paper, a reverse-biased p.s.d. structure is presented, and an overall linearity better than 0.5% full scale and a photosensitivity of 1.5 A/W for an He-Ne laser were obtained.
Abstract: Based on the lateral photoeffect it is possible to construct photodetectors of which the output is dependent on the light-spot position. In the literature, a number of these position-sensitive detectors (p.s.d.) based on the forward or reverse characteristics of a photodiode have been presented. The integration of a p.s.d. with signal processing circuits on one silicon chip may eventually lead to very versatile, high-quality low-cost sensors. Therefore it is necessary to develop a p.s.d. structure which can be fabricated with standard planar silicon technology. In this paper such a novel reverse-biased p.s.d. structure is presented. A 6 × 6 mm2 p.s.d. was made, and an overall linearity better than 0.5% full scale and a photosensitivity of 0.5 A/W for an He-Ne laser were obtained. The dependence of the position sensitivity on background illumination and temperature as well as resolution are similar to those of currently known linear p.s.d.s.
TL;DR: In this paper, a comparison of fatigue tests on centrally cracked specimens and lug type specimens, both made from solid sheet and laminated sheet, consisting of five 1 mm sheets of 2024-T3 Alclad material bonded by FM 123/5.
TL;DR: In this article, the Navier-Stokes equations and the continuity equation were solved for uniform evaporation and condensation rates in a horizontal flat plate heat pipe with an adiabatic top plate.
Abstract: Steady laminar incompressible two-dimensional flow in a horizontal flat plate heat pipe with an adiabatic top plate was studied. For uniform evaporation and condensation rates, the Navier-Stokes equations and the continuity equation were solved. For radial Reynolds numbers Rer > 1, the velocity profiles were nonsimilar and asymmetrical. At Rer > 10, backflow was observed along the top plate, starting at the end of the condensation zone. At the highest /?er( = 50), the total pressure drop over the heat pipe was more than three times the value found from Poiseuille approximation. However, complete recovery of impulse pressure was found and the additional pressure losses could be fully attributed to increased frictional losses. Experiments with a porousplate model showed excellent agreement.
TL;DR: The ultrastructure of Spirulina platensis, a cyanobacterium with a helical morphology, has been studied in relation to temperature and light intensity and cylindrical bodies have been observed with a somewhat different ultrast structure from those found in other species of cyanobacteria.
Abstract: The ultrastructure of Spirulina platensis, a cyanobacterium with a helical morphology, has been studied in relation to temperature and light intensity. An increase in temperature gives rise to a more tightly coiled trichome, an increase in sheath material formation and a decrease in cyanophycin (above 17°C) and polyglucan (above 20°C) granule concentration. An increase in light intensity leads to an increase in gas vesicle concentration while the phycobilisome content decreases. Furthermore, cylindrical bodies have been observed with a somewhat different ultrastructure from those found in other species of cyanobacteria. The occurrence, size and ultrastructure of polyhedral bodies, photosynthetic lamellae, mesosomes, lipid deposits and an unknown kidney-shaped inclusion in relation to temperature and light intensity are described.
TL;DR: In this paper, the authors compared the residence time distribution of a twin screw extruder with a model based on ideally mixed chambers, and special attention was given to the tail of the distribution.
Abstract: Residence time distribution measurements in a twin screw extruder are compared with a model based on ideally mixed chambers. Special attention is given to the tail of the distribution. These measurements are compared with the residence time distributions in single screw extruders and an empty pipe.
TL;DR: In this article, a dc converter for the drive and control of a 45-kW traction motor in single quadrant operation with an efficiency of 96 percent is presented, which is due to the natural termination of thyristor currents, the positive confinement of the maximum momentary current and voltage stresses in the components below preset levels, and the low power dissipation in these components supported by a definite protection philosophy.
Abstract: A new type of dc converter for the drive and control of a 45-kW traction motor in single quadrant operation with an efficiency of 96 percent is presented. An improvement of the converter's reliability is due to the natural termination of thyristor currents, the positive confinement of the maximum momentary current and voltage stresses in the components below preset levels, and the low power dissipation in these components, supported by a definite protection philosophy. The high converter efficiency is attained at full power operation with an internal frequency of 10 kHz. The input impedance maintains its resistive character for all conditions of operation. The output port is characterized as a voltage-limited current source. Test data of an experimental model conclude the presentation of the converter's functional philosophy.