Showing papers by "Delft University of Technology published in 1975"
TL;DR: In this paper, an analysis of the vortex field in terms of a solution to the simplified Navier-Stokes equations shows reasonable agreement with the measured velocity profiles, and pressure field determinations at two different scales prove that Reynolds number alone is a sufficient scale-up parameter.
220 citations
TL;DR: A classification and characterization of the more important transport phenomena in macroporous media (molecular diffusion, viscous flow, transport phenomena involving moving menisci: wetting, capillary rise, drainage, drying) is given in this paper.
194 citations
TL;DR: It must be concluded that the protective role of glutathione is only significant when a chemical challenge is present.
172 citations
TL;DR: In this paper, two methods of adaptation are compared with respect to the sensitivity model and Liapunov approach for a ship with a constant thrust power, and the results were tested in practice on this ship.
121 citations
TL;DR: The fine structure of the turbulence is strongly associated with and dominated by the random, larger-scale, intermittent inrush-ejection cycle as discussed by the authors, and the change in the mechanism of the fine structure with distance from the wall is clearly demonstrated by the spectra of non-negative variables, i.e.
Abstract: Measurements have been made concerning the fine structure of the turbulence in the part adjacent to the wall of the wall region of a plane turbulent boundary layer. The objective was to gain further information concerning the larger-scale disturbance mechanism which is mainly responsible for the generation of turbulence. Hot-wire anemomet.ry was used and information on the fine structure was obtained by differentiating and filtering the hot-wire signal.The distributions of the Kolmogorov microscale and of the flatness and skewness factors of the axial fluctuating velocity u and its first and second derivative determined at two Reynolds numbers suggest the existence of Reynolds number similarity. In the region y+ 100) the flatness and skewness factors approach values obtained in shear-free turbulence at the same turbulence Reynolds number.The fine structure of the turbulence is strongly associated with and dominated by the random, larger-scale, intermittent inrush-ejection cycle. In the viscous sublayer both the fine structure, and the large-scale mechanism of the turbulence are influenced mainly by the inrush phase, while further out in the wall region (y+ > 40) they are influenced by both inrush and ejection. As a result, in the viscous sublayer the average burst periods of the high frequency turbulence components and their flatness factors (of ∂u/∂t and of ∂2u/∂t2) attain values twice those in the outer part.The change in the mechanism of the fine structure with distance from the wall is clearly demonstrated by the spectra of non-negative variables, i.e. (∂u/∂t)2 and (∂2u/∂t2)2. The spectra agree with each other and decrease with increasing frequency, following a power law as predicted by Gurvich & Yaglom (1967). The power law applies to almost the whole frequency range, when the highest, viscous, frequency range is excluded. However, the exponent is different for the viscous sublayer and the outer part of the wall region. In the buffer layer the spectra have two distinct power-law regions. In the lower frequency range the exponent is the same as that for the viscous sublayer, while in the higher frequency range it is the same as that for the outer part of the wall region.
119 citations
TL;DR: In this paper, the authors analysed the sediment of the shelf off Walvis Bay (S.W. Africa) for lipid material and found that the lipid contents consist of a mixture of hydrocarbons, alcohols, ketones, fatty acids, sterols, carotenoid pigments and chlorophylls.
117 citations
TL;DR: The levels of the enzymes remained constant, indicating that glutathione biosynthesis depends at least in the beginning on the availability of the component amino acids, and the pathway is controlled by feedback inhibition and not by repression.
109 citations
TL;DR: In this article, two crystal growth models, the step model (BCF) and the nuclei model (NaN), were used to quantify the resistance to crystal growth offered by volume diffusion and the optimum distribution of experimental points required both to ensure the maximum possible accuracy of the derived parameters in the growth equations and to discriminate between the two models.
94 citations
TL;DR: In this article, a mass transfer model which describes oxygen transfer from bubbles under a water surface created by the impact of a plunging water jet is proposed, which leads to the conclusion that direct application to waste water treatment may be promising, especially when the relative simplicity of the equipment is considered.
68 citations
TL;DR: In this paper, it was demonstrated that simple similarity criteria which can be satisfied experimentally can be derived from the conventional equations governing liquid flows, which are susceptible to experimental verification and potentially useable for the scaling of flows.
58 citations
TL;DR: In this article, the authors quantified the crystallinity of minerals in terms of crystallite size distribution and lattice perfection by means of statistical measures derived from X-ray line profiles (2 cr values).
Abstract: The crystallinity of minerals in terms of crystallite size distribution and lattice perfection is quantified by means of statistical measures derived from X-ray line profiles (2 cr values). A low degree of crystallinity facilitates the non-stoichiometric incorporation of foreign elements in the crystal lattice. Crystallinity is affected by a number of factors and in natural profiles it may vary laterally as well as vertically. For instance, goethite in laterite deposits shows decreasing crystallinity with increasing depth. Serpen- tine type minerals, on the other hand, show the lowest crystallinity at the surface where the degree of weathering is the most advanced. The presence of silica in migrating solutions prevents crystal growth and results in a low degree of crystallinity of minerals such as goethite. This has been observed in natural profiles and has been confirmed by laboratory experiments on the synthesis of goethite and sodium-birnessite. The crystallinity of minerals affects their response to extractive procedures. It could also be an important parameter in soil science.
TL;DR: In this paper, the porespace in a porous medium is visualised as a more or less complicated assembly of isolated or interconnected capillaries, and such pore space models are used in describing transport phenomena in porous media.
Abstract: USUALLY the porespace in a porous medium is visualised as a more or less complicated assembly of isolated or interconnected capillaries, and such porespace models are used in describing transport phenomena in porous media. If capillary rise of a (wetting) liquid in a homogeneous irregular packing of rotund particles is considered, however, it seems that none of the existing porespace models is capable of explaining, not even qualitatively, the observed phenomena1.
TL;DR: In this article, the conformation of bicyclo[3.3.1]nonane-3α,7α-dicarboxylic acid and its dimethyl ester has been studied by comparing 1 H NMR and 13 C NMR spectra of these compounds with those of some model 3,7-disubstituted bicyclo
TL;DR: In this paper, the influence of volume diffusion on crystal growth rates is investigated theoretically and two models for combined volume and surface diffusion are considered, and their implications compared, and it is found that the model in which volume and surfaces diffusion are put in series gives a good description for growth from solution.
01 Jan 1975
TL;DR: In this paper, a single pre-strain ( ϵ = 0.03 ) applied to 2024-T3 material raised the static yield strength from 428 to 480 MN/m 2.
Abstract: A single pre-strain ( ϵ = 0.03 ) applied to 2024-T3 material raised the static yield strength from 428 to 480 MN/m 2 . The growth rate of a fatigue crack in the pre-strained material was about twice as large as in the material that was not pre-strained. A pre-strain followed by 1000 high, but still elastic pre-stress cycles did not further increase the growth rate. It was shown by COD measurements that crack closure occurred to a lesser extent in the pre-strained material as compared to the original material. The significance of the increased yield strength for fatigue crack growth is briefly discussed.
TL;DR: In this paper, the paramagnetic praseodymium ion shifted the resonances downfield in a regular way and allowed the identification of all the signals and the determination of the coupling constants.
Abstract: Complexation of ten alditols with praseodymium(III) [isosteric with calcium(II)] as the model cation has been studied in aqueous solution by 1H-NMR. The paramagnetic praseodymium ion shifted the resonances downfield in a regular way and allowed the identification of all the signals and the determination of the coupling constants.
The following configurational sequence of tridentate ligands (H-COH), with respect to complex formation with PrIII has been established: xylo > threo > arabino (lyxo) > glycerol > erythro, ribo. Two major effects appear to be operative: (i) secondary hydroxyl groups show better complexation than primary hydroxyl groups; (ii) gauche butane and 1,3-dihydroxyl repulsions introduced upon complexation cause a decrease of the complex stability.
Conformational data of both the uncomplexed and the complexed state in aqueous solution have been obtained from the vicinal coupling constants.
TL;DR: In this article, a principle for absolute voltage division is presented, which does not depend on the values of its elements but depends exclusively on the configuration of the divider network, hence, calibration is not necessary and not even possible.
Abstract: In this paper, a principle for absolute voltage division is presented. The division ratio of a voltage divider on this principle does not depend on the values of its elements but depends exclusively on the configuration of the divider network. Hence, calibration is not necessary and not even possible. Absolute voltage division is obtained by cyclically shifting the network elements along all positions in the divider network. Each position is maintained for an equally long time interval. The average output voltage of such a dynamic divider is identical to that of a static divider with the same network configuration but composed of elements which all have the same value. To verify the principle in practice, a digitally controlled resistive voltage divider has been built. It has been realized with easily available electronic components, such as carbon resistors with ± 5-percent tolerance, junction field-effect transistors as electronic switches and digital integrated circuits for the generation of the switch drive signals. The inaccuracy of this divider is less than 5 ×10-6 and the temperature coefficient of the division ratio is less than 5 × 10-8/°C from 0°C to 40°C. It is expected that the performance, of this prototype can be improved.
TL;DR: Vibrio alginolyticus strains recently isolated from Dutch coastal seawater changed flagellar organization when cultivated in the presence of certain chemical agents.
TL;DR: The absorption spectrum of the enzyme exhibited a marked absorption band in the 400-460 nm region in addition to protein absorption, and according to polyacrylamide gel electrophoresis the final preparation was virtually homogeneous.
TL;DR: The present paper examines one of the foundation problems of Cybernetics: the principles of representing entities and the relations between them by systems of symbols, which are treated as extensions and generalizations of the fundamental concepts of measurement.
Abstract: The study of information is central to the science of Cybernetics. The communication and processing of information takes place, in general, by means of signals, which represent or describe (in other words symbolize) the entities to which the information relates. The present paper examines one of the foundation problems of Cybernetics: the principles of representing entities and the relations between them by systems of symbols. It treats these principles as extensions and generalizations of the fundamental concepts of measurement.
TL;DR: In this article, the current state of understanding of the epistemological and logical foundations of measurement is discussed, and the conditions for the establishment of scales of measurement are analysed, as well as the conditions of scale-based measurement.
Abstract: The paper presents briefly the current state of understanding of the epistemological and logical foundations of measurement. Measurement is defined as an empirical operational procedure which assigns numbers to members of a class of entities, in such a way as to describe them; by which is meant that relations between these numbers correspond to empirical relations between the entities to which they are assigned.On the basis of this definition, the conditions for the establishment of scales of measurement are analysed.
TL;DR: The mechanism of the degradation of phytol to phytanic acid is still uncertain this paper, but at least two pathways have been proposed and shown to occur in some cases.
Abstract: PHYTANIC acid and several lower isoprenoid acids are found in the marine food chain and in sediments. The mechanism of the degradation of phytol to phytanic acid is still uncertain. At least two pathways have been proposed and shown to occur in some cases1. One by way of dihydrophytol, another by phytenic aldehyde and phytenic acid. Phytenic acid was postulated recently2 as intermediate in the degradation of phytol in sediments and was mentioned among isoprenoid compounds in Mud Lake sediment3. It is formed from phytol thermo-catalytically in oxic conditions4.
TL;DR: In this paper, a brief survey of progress in the scientific analyses of human capabilities, limitations, needs and motivations is given, and experimental techniques specific to the social sciences are touched upon.
TL;DR: In this paper, the longitudinal and transverse relaxation rates of the individual lines in a HRNMR proton AX2 spectrum were investigated and the relaxation mechanisms considered are dipolar and scalar interactions.
Abstract: Expressions are given for the longitudinal and transverse relaxation rates of the individual lines in a HRNMR proton AX2 spectrum. The relaxation mechanisms considered are dipolar and scalar interactions. Measurements are performed on the proton spectra of dilute degassed solutions of 2-amino pyrimidine in acetone-d6/D2O. The relative values are determined of the interproton distances in the AX2 system and of three rotational diffusion constants, Dxx , Dyy and Dzz . Two coupling constants between the ring protons and the 14N ring nitrogens are found to be 10·3 and 2·2 Hz.
TL;DR: Pore size distributions in iron oxide-chromium oxide, compressed Aerosil, zirconia powder, and loosely packed and compressed chrysotile have been determined by nitrogen capillary condensation (corrected Kelvin equation) and mercury penetration as mentioned in this paper.
TL;DR: The electronic implementation of the detection procedure is dedicated to the extraction of the left ventricular contour out of angiographs, and will lead to a considerable time saving and improved reproducibility.
Abstract: Structures characterized by a brightness contour can be automatically detected when the information is carried by a video signal. The detection system described here processes the available position and brightness information of the picture in a way closely related to the features of such structures. Real time processing of the picture information is made possible by the use of very simple memories. The electronic implementation of the detection procedure is dedicated to the extraction of the left ventricular contour out of angiographs. Compared with manual contour tracking the application in diagnostic cardiology will lead to a considerable time saving and improved reproducibility.
TL;DR: Water samples, collected along the Dutch coast, were examined for the presence of marine vibrios and Vibrio parahaemolyticus biotype 2 was isolated; 4 of these isolates were methyl red-positive, and 2 other isolate were arabinose-positive.
TL;DR: In this paper, the thermal behavior of compounds with formula Ni(Iz)n(X)2, with Iz = imidazole, n = 1, 2, 4 and 6, and X = Cl, Br, I, NCS, has been studied with the aid of differential thermal analysis (DTA), thermogravimetry (TG) and X-ray powder diffraction in the temperature region 20-600°C.
TL;DR: In this paper, the maximum error of the position of a black straight line with rectangular profile on a white background is determined as a function of the number of equidistant gray levels used.
TL;DR: In this article, the structure and texture of chrysotile and garnirite were studied by electron microscopy, and a method was indicated by which the internal pore size distribution in such preparations can be calculated.