Showing papers by "Delft University of Technology published in 1976"
TL;DR: Parzen estimators are often used for nonparametric estimation of probability density functions and a problem-dependent criterion for its value is proposed and illustrated by some examples.
Abstract: Parzen estimators are often used for nonparametric estimation of probability density functions. The smoothness of such an estimation is controlled by the smoothing parameter. A problem-dependent criterion for its value is proposed and illustrated by some examples. Especially in multimodal situations, this criterion led to good results.
364 citations
TL;DR: Fuzzy algorithms based on linguistic rules describing the operator's control strategy are applied toControl of a warm water plant using fuzzy set theory.
299 citations
TL;DR: In this paper, a converter philosophy for controlled transfer and transformation of electric energy through internal series resonant circuits at high internal power frequencies in excess of 10 kHz is presented, which is suited for construction of failsafe and highly efficient, low cost, submegawatt, single module converters with currently available components.
Abstract: Presented is a converter philosophy for controlled transfer and transformation of electric energy through internal series resonant circuits at high internal power frequencies in excess of 10 kHz. Control of the continuously oscillating high Q series resonant circuit is attained by adjustment of the phase angle ? r between the exciting voltage and the resonant current. Only a very small fraction of the energy transferred to the load is absorbed by the resonant circuits to replace the power dissipated therein. Moderate and unconditionally predictable voltage and current stresses on components result from definite control of static and dynamic behavior of the system. This system is suited for construction of failsafe and highly efficient, low cost, submegawatt, single module converters with currently available components.
195 citations
TL;DR: In this paper, the authors studied similarity solutions of (1) in S, of the following three types: weak Cauchy-Dirichlet problem, weak Dirichlet-Cauchy problem, and weak version.
123 citations
TL;DR: In this article, the axial dispersion coefficients for helical coiled tubes were calculated for Dean numbers smaller than 16, and the ratio of the dispersion coefficient in coiled tube to that in straight tubes can with good approximation be given as a function of Dn2Sc, provided R/a > 20.
102 citations
TL;DR: In this paper, the authors developed equations for air entrainment by plunging water jets with velocities in the range between 2 and 5 m/sec. Energy considerations are shown to be a good basis for predictive equations.
100 citations
TL;DR: In this paper, the total potential of unsaturated flows is expressed as the sum of a hydrostatic potential due to capillary suction 0(0) and a gravitational potential −3, 10, 11.
Abstract: Here K(O) is the hydraulic conductivity, ~b is the total potential and t denotes time. If adsorption and chemical, osmotic and thermal effects are neglected, then for unsaturated flows 9 may be expressed as the sum of a hydrostatic potential due to capillary suction 0(0) and a gravitational potential [-3, 10, 11]. Thus if we choose our (x, y, z) coordinate system in such a way that the z-coordinate is vertical, and pointing upwards, we may write
99 citations
TL;DR: In this article, a survey of variable-amplausitude loading as applied in test programs is given, with an analysis of the consequences for prediction techniques. But the authors focus on the effects of variableamplitude loading on fatigue cracks.
Abstract: The paper starts with a discussion on loads in service, after which a survey is given of various types of variable-amplitude loading as applied in test programs. The various phenomenological aspects of fatigue damage associated with fatigue cracks are indicated. Interaction effects between cycles of different magnitudes are defined. Methods for measuring interaction effects, examples of interaction effects, and possible explanations are reviewed. This includes both tests with simple types of variable-amplitude loading (overloads and step loading) and more complex load-time histories (program loading, random load, and flight-simulation loading). New evidence on crack closure is presented. Various types of prediction methods are discussed. The paper is primarily a survey of the present knowledge, with an analysis of the consequences for prediction techniques.
88 citations
TL;DR: In this article, it is shown that the ordered pseudo turbulence deviates so much from isotropic conditions that the usual interpretation in terms of the turbulence parameters of scale intensity is of doubtful value in this region.
84 citations
TL;DR: This set of some 1300 values presented here is a revision of the 1971 Atomic Mass Evaluation made in the light of recent results, but does not constitute a new analysis of comparable carefulness.
67 citations
TL;DR: In this article, the authors compared the results obtained in chemical and organoleptic analysis of the same extract and found that the natural (-)-form of 1-octen-3-ol had a stronger flavour than the (+)-form and was the most important aroma component.
Abstract: The flavour ofAgaricus bisporus was studied by comparing the results obtained in chemical and organoleptic analysis of the same extract. The natural (-)-form of 1-octen-3-ol had a stronger flavour than the (+)-form and was the most important aroma component. Nucleotides, amino-acids and carbohydrates also contributed significantly. Benzaldehyde, benzyl alcohol, 1-octen-3-one,n-butyric and isovaleric acids as well as low-boiling volatiles contributed less to the flavour. A synergistic effect of nucleotides, carbohydrates and (-)-1-octen-3-ol on the flavour was not observed.
TL;DR: In this paper, the chemical shift increments of the aromatic protons on complex formation of C6H5CH-t-Bu2, as a reference for the eclipsed conformation with the substituent staggered with respect to the carbonyl ligands, have been used to estimate the contribution of this conformer to the conformational equilibrium of the other monoalkylsubstituted complexes.
TL;DR: In this article, the transient behavior of an adiabatic fixed-bed catalytic reactor has been studied experimentally and theoretically using the hydrogenation of small amounts of CO and CO 2 to methane as the test reactions.
TL;DR: In this paper, the so-called stress-optical law is checked with the aid of flow birefringence technique, which is used for the analysis of polymer melts.
Abstract: Transient stresses including normal stresses, which are developed in a polymer melt by a suddenly imposed constant rate of shear, are investigated by mechanical measurement and, indirectly, with the aid of the flow birefringence technique. For the latter purpose use is made of the so-called stress-optical law, which is carefully checked.
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.
TL;DR: In this paper, a dc converter for sub-megawatt applications is described and illustrated with the characteristics of a small scale 10 kW model, which is characterized by the behavior of a true current source with inherent short circuit capability of its output terminals.
Abstract: A type of industrial size dc converter for submegawatt applications is described and illustrated with the characteristics of a small scale 10 kW model. High conversion efficiency near 97 percent is maintained at full power and with an internal frequency of operation near 10 kHz. The system is characterized by the behavior of a true current source with inherent short circuit capability of its output terminals. All power is processed via a firmly controlled high Q series resonant circuit. Feasibility of power densities in excess of 1 kW/kg component weight is demonstrated. This high power density reflects itself in low quantities of material needed for construction of these systems. Operation of the dc converter as part of a rectifier-filter converter system, powered from a three-phase supply line is described. Test data demonstrate a high power factor PF?0.95 for all conditions of converter loading. Data obtained from a thyristor bridge-filter system are presented and subjected to comparative analysis.
TL;DR: In this article, a higher-order lifting-line theory for a wing in unsteady motion is discussed, which differs from the theory derived by James (1975) in its emphasis on physical interpretations.
Abstract: A higher-order lifting-line theory for a wing in unsteady motion is discussed. Apart from the addition of higher-order terms, it also differs from the theory derived by James (1975) in its emphasis on ‘physical’ interpretations. This emphasis has made it possible to shed some new light on Prandtl's classical lifting-line theory, as well as on Weissinger's 3/4-chord theory.
29 Jan 1976
TL;DR: In this article, the direction of net sand transport depends upon the form of the waves, and the measured sand transport is related to the measured wave form parameters, and it is shown that the transport has been measured by means of a special procedure which does not disturb the process.
Abstract: Sand transport parallel to the direction of wave propagation by waves of arbitrary form over a rippled bed has been investigated in a flume, at the Laboratory of Fluid Mechanics of the Dept. of Civ. Eng. of the Delft Univ. of Techn. The transport has been measured by means of a special procedure which does not disturb the process. The measured sand transport is related to the measured wave form parameters. The results indicate that the direction of net sand transport depends upon the form of the waves.
01 Jan 1976
TL;DR: In this article, the influence of the supersaturation and the size of the crystals on the growth rate of K2Cr2O7 has been investigated and it has been shown that after an experiment, a spread in sizes was present when the increase in size was large.
Abstract: In our laboratory some experiments with K2Cr2O7 crystals in a fluidized bed have been carried out in order to determine the influence of the supersaturation and the size of the crystals on the growth rate. It was found that the growth rate of the crystals increased with size (see Table 1). Furthermore it appeared that after an experiment a spread in sizes was present. This was observed when the increase in size was large (Fig. 1). As seed crystals with a narrow size range were used it can be concluded that the increase in size and as a consequence the growth rate differs from crystal to crystal. As the supersaturation was kept constant within 5% the only reasonable explanation is that crystals of one size exhibit a spread in growth rates. We have called this phenomenon ‘growth dispersion’.
TL;DR: Using well-known principles a configuration has been developed for an IC reference voltage source with good performance with respect to the temperature dependency and 1/f noise and a bread-board model of this configuration has be tested.
Abstract: Using well-known principles a configuration has been developed for an IC reference voltage source with good performance with respect to the temperature dependency and 1/f noise. A bread-board model of this configuration has been tested. In the temperature range of 0-70/spl deg/C, the output voltage variations were less than /spl plusmn/70 ppm at an output voltage of about 2.5 V and zero load current. Low-frequency noise in a bandwidth 0.003 Hz
TL;DR: In this article, a modified cone-and-plate apparatus was designed for the measurement of the flow birefringence of polymer melts in a wide range of shear rates.
Abstract: A description is given of a modified cone-and-plate apparatus designed for the measurement of the flow birefringence of polymer melts in a wide range of shear rates. Results are given of measurements on samples of high and low density polyethylene and polystyrene. Anomalies, as found in the extinction angle curves near the fringes, where the phase differences become equal to multiples of 2π, point to pronounced edge effects which appear to depend on the type of polymer. The measurements on the high density polyethylene were used to check the validity of the stress-optical law. The measurements on the low density polyethylene sample show mechanical degradation of this polymer. Some typical transient measurements on the polystyrene sample are presented and successfully related to the corresponding mechanical measurements, as obtained with the aid of a cone-and-plate Weissenberg rheogoniometer.
TL;DR: The resistivity method has proved to be very suitable in determining the distribution of fresh and saline groundwater in sedimentary deposits as occur in the Netherlands as discussed by the authors, however, the method gives no information about recharge, groundwater flow, geohydrological constants (permeability, transmissibility and hydraulic resistance) and the presence of relatively thin layers of bad hydraulic conductivity.
TL;DR: In this paper, the shape of the out-of-phase band is influenced by electronic effects, conformer distribution and solute-solvent interaction, and the asymmetry of the E-band in (1'-t-butyl-2',2'-dimetliylpropyl)-7r-(tricarbonylchromium)benzene is ascribe to a direct steric effect.
TL;DR: In this paper, the transient behaviour of an adiabatic fixed-bed methanator was studied using the hydrogenation of mixtures of CO and CO2 at concentrations up to 2·7 vol.% carbon oxide in hydrogen as the test reactions.
TL;DR: The design of a monolithic operational amplifier, which combines a large bandwidth and a high output current, is described, and provides the possibility for achieving higher output currents.
Abstract: The design of a monolithic operational amplifier, which combines a large bandwidth and a high output current, is described. The output stage is equipped with n-p-n transistors only, biased in class-AB by an internal common-mode feedback loop. The intermediate stage consists of a unity-current-gain split-frequency-band voltage level shift. An integrated version, intended for driving 50-/spl Omega/ coaxial line systems, achieves a bandwidth of 25 MHz and 100-mA output current. The principle described provides the possibility for achieving higher output currents.
29 Jan 1976
TL;DR: In this article, the authors present empirical results concerning the above-mentioned flow parameters, obtained from experiments with periodic waves breaking on smooth plane slopes, and considerable attention is given to similarities in the run-up process; the existence of such similarities had previously been inferred from Hunt's formula for the maximum runup height.
Abstract: The run-up of waves is an important factor in the design of shore structures. It has been investigated in many studies, both theoretical and experimental. The experimental studies have mostly been confined to the maximum run-up (the greatest height above still water level, reached by the periodic waves on the slope). A simple and reliable formula for the maximum run-up is given by Hunt (I), based on measurements with periodic waves breaking on smooth plane slopes. However, virtually no data are available regarding the characteristics of the flow in the up-rush and the down-rush on a smooth slope, such as layer thickness, particle velocity, wave front velocity, and so on. Such information can be of use in developing or adjusting schemes for numerical calculation of run-up and overtopping, as well as in problems of stability of cover layer material or of seepage of water into the core material of a dike. The purpose of this report is to present empirical results concerning the above-mentioned flow parameters, obtained from experiments with periodic waves breaking on smooth plane slopes. In the analysis of the data considerable attention is given to similarities in the run-up process; the existence of such similarities had previously been inferred from Hunt's formula for the maximum run-up height.
TL;DR: In this article, a coaxial cylinder was used for the measurement of flow birefringence of polymer melts at extremely low shear rates (10−3 s−1) under transient conditions.
Abstract: A description is given of a coaxial cylinder apparatus, suitable for the measurement of the flow birefringence of polymer melts at extremely low shear rates (~10−3 s−1) and, in particular, under transient conditions.
TL;DR: In this article, the length of phase-slip centers is determined by inelastic scattering of quasiparticles and the relaxation time is found to be about 10 −7 s independent of temperature.
TL;DR: A number of coordination compounds with general formula M(LL)n(anion)2Sx have been prepared, in which M stands for Co, Ni, Cu(II), Mn, Zn and Cd, LL = thiazolylbenzimidazole, the anions are ClO4−, BF4 −, NO3−, Cl− and Br−, S stands for water or ethanol.
TL;DR: The concentrations of 1-octen-3-ol, 5′-GMP and glutamic acid were compared in 8 fresh, 3 canned and 5 dried mushroom species and Glutamic acid was present in most samples in sufficient quantities to have an important influence on the flavour.
Abstract: The concentrations of 1-octen-3-ol, 5′-GMP and glutamic acid were compared in 8 fresh, 3 canned and 5 dried mushroom species. The highest amounts of 1-octen-3-ol and 5′-GMP were found in the fresh mushrooms.Agaricus bitorquis, Pleurotus ostreatus andPholiota squarrosa contained 5–7 times as much 1-octen-3-ol asAgaricus bisporus andCalvatia gigantea 58 times as much.Coprinus comatus andPleurotus ostreatus contained much 5′-GMP. Little 1-octen-3-ol and 5'-GMP were found in most dried and canned mushrooms. Potatoes and tomatoes were analyzed for comparison. Little or no 1-octen-3-ol and 5′-GMP were observed. Glutamic acid was present in most samples in sufficient quantities to have an important influence on the flavour.