Showing papers by "Technical University of Denmark published in 1973"
254 citations
TL;DR: In this article, a digital model has been developed for the simulation of the rainfall-runoff process of rural watersheds, which produces daily values of streamflow as well as information on the time variation of the soil moisture content.
Abstract: A digital model has been developed for the simulation of the rainfall-runoff process of rural watersheds. Input data are daily values of precipitation and temperature together with mean monthly potential evapotranspiration. The model produces daily values of streamflow as well as information on the time variation of the soil moisture content. In all, ten model parameters have to be identified, seven of which have a major influence on the performance of the model. The model operates by accounting continuously for the moisture content in four different and mutually interrelated storages representing physical elements in the watershed. It has been applied to three different Danish watersheds. Several statistical measures of accuracy have been utilized for a quantitative evaluation of the simulation results. The simulations demonstrate that the main shortcomings of the model are due to the lack of a procedure accounting for frozen ground during extended periods of frost, which could improve some of the simulation results during winter and spring.
245 citations
TL;DR: It is shown that the polynomials (x - c)^i, i = 0,1,2,\cdots, have the "weight-retaining" property that any linear combination of these polynmials with coefficients in GF(q) has Hamming weight at least as great as that of the minimum degree polynomial included.
Abstract: For any nonzero element c of a general finite field GF(q) , it is shown that the polynomials (x - c)^i, i = 0,1,2,\cdots , have the "weight-retaining" property that any linear combination of these polynomials with coefficients in GF(q) has Hamming weight at least as great as that of the minimum degree polynomial included. This fundamental property is then used as the key to a variety of code constructions including 1) a simplified derivation of the binary Reed-Muller codes and, for any prime p greater than 2, a new extensive class of p -ary "Reed-Muller codes," 2) a new class of "repeated-root" cyclic codes that are subcodes of the binary Reed-Muller codes and can be very simply instrumented, 3) a new class of constacyclic codes that are subcodes of the p -ary "Reed-Muller codes," 4) two new classes of binary convolutional codes with large "free distance" derived from known binary cyclic codes, 5) two new classes of long constraint length binary convolutional codes derived from 2^r -ary Reed-Solomon codes, and 6) a new class of q -ary "repeated-root" constacyclic codes with an algebraic decoding algorithm.
207 citations
TL;DR: In this article, a hydrodynamic stability analysis of the flow in an alluvial channel in which dunes have developed along the bed is presented, and the model offers an explanation of the fact that some channels tend to meander, others to braid.
Abstract: The paper describes a hydrodynamic stability analysis of the flow in an alluvial channel in which dunes have developed along the bed. The purpose is to develop a mathematical model describing the three-dimensional flow leading to instability of an originally straight channel. The model offers an explanation of the fact that some channels tend to meander, others to braid.
176 citations
TL;DR: The correlation between extraction data and electrode behaviour assisted in explaining the vital properties of organophosphate-based calcium electrodes, and in suggesting a new liquid ion exchanger, di-(n-octylphenyl) phosphoric acid as discussed by the authors.
170 citations
TL;DR: In this paper, a potassium electrode utilizing a solution of valinomycin in diphenylether and a porous membrane is compared with selectrodes in which the diphenylther has been replaced by a suitable plasticizer and the porous membrane support by a polymer net-work.
161 citations
TL;DR: In this article, the initial postbuckling behavior of an integrally stiffened wide panel under compression was determined for a wide Euler column and local buckling of the plates between the stiffeners.
116 citations
TL;DR: The compositional trends in groups IIIA and IIIB are redefined, and the suggestion by Wasson and Kimberlin that they represent a single fractionation sequence (group IIIAB) is confirmed as discussed by the authors.
114 citations
TL;DR: In this article, the Amonton friction law does not apply when normal pressure is higher than approximately the yield stress of the specimen; in this case it is necessary to consider the frictional stress as a function of normal pressure, surface topography, length of sliding, viscosity, and compressibility of the lubricant.
98 citations
TL;DR: In this article, a comparison between the antenna pattern comparison technique and the free-space voltage standing-wave ratio technique for evaluating the reflectivity level of radio anechoic chambers is presented.
Abstract: A comparison between the antenna-pattern comparison technique and the free-space voltage standing-wave ratio technique for evaluating the reflectivity level of radio anechoic chambers is presented. Based on an analysis of the two techniques, it is pointed out which parameters influence the measured value of the reflectivity level. The comparison is illustrated with experimental results and it is explained why inconsistent and uncorrelated results may be found when the two methods are used. Furthermore, it is demonstrated, by introducing improvements in a chamber, how the reflectivity level can be used to measure the improvements. This work is inspired by the current discussion of finding a figure of merit for anechoic chambers. Based on the results, an evaluation procedure for anechoic chambers is indicated. However, it is pointed out and illustrated by examples that further investigations are necessary before a satisfactory procedure can be outlined.
93 citations
TL;DR: One suboptimum synchronizer, which is extremely simple to instrument, is shown to perform virtually optimally over the entire range of interesting signal-to-noise ratios.
Abstract: In this correspondence we investigate the performance of several optimum and suboptimum devices for locating a sync word in data corrupted by Gaussian noise. One suboptimum synchronizer, which is extremely simple to instrument, is shown to perform virtually optimally over the entire range of interesting signal-to-noise ratios.
TL;DR: In this paper, a new laser line is observed in electron beam excited ZnO at temperatures below 77 K. The laser wavelength is 3726 A at 10 K, and the corresponding spontaneous emission band (P-band) contains two pronounced peaks at 3715 and 3730 A, respectively.
TL;DR: In this paper, the authors determine the optimum tapering of a cantilever carrying an end mass, i.e., the shape which yields the highest possible value of the first fundamental frequency of harmonic bending vibrations in the vertical plane.
Abstract: We determine the optimum tapering of a cantilever carrying an end mass, i.e., the shape which, for a given total mass, yields the highest possible value of the first fundamental frequency of harmonic bending vibrations in the vertical plane.
TL;DR: In this article, an iterative procedure for determining the joint positions corresponding to a minimum mass space truss is presented, which includes a sequence of linear programming problems (SLP, with move-limits), and for each of these problems only the nearby constraints are considered.
Abstract: An iterative procedure for determining the joint positions corresponding to a minimum mass space truss is presented. Displacement constraints and nonconstant stress constraints (stability) are taken into account. The truss is presumed to carry consecutively a large number of different systems of forces. The iteration includes a sequence of linear programming problems (SLP, with move-limits), and for each of these problems only the nearby constraints are considered. Analytical expressions are given for the gradients describing the linear problems. A dome is optimized using different constraints.
01 Jan 1973
Abstract: An expression is obtained for the expected duration of a search to find a given L -ary sequence in a semi-infinite stream of random L -ary data. The search time is found to be an increasing function of the lengths of the "bifices" of the pattern, where the term bifix denotes a sequence which is both a prefix and a suffix.
01 Jan 1973
TL;DR: A class of lower bounds to ratedistortion functions of stationary sources with context-dependent fidelity criteria is derived by mapping the source and distortion measure into an equivalent restrictedtransition stationary source with a single-letter fidelity criterion, and then applying the composite bound.
Abstract: A class of lower bounds to ratedistortion functions of stationary sources with context-dependent fidelity criteria is derived by mapping the source and distortion measure into an equivalent restrictedtransition stationary source with a single-letter fidelity criterion, and then applying the composite bound. This approach is seen to yield bounds which, although sometimes quite loose, apply to general stationary sources and context-dependent fidelity criteria. Two examples are presented. Rate-distortion theory is usually restricted to single-letter fidelity criteria due to the complexity of more general cases. In many cases, however, the fidelity of the reproduction depends on the context of the message. To take context into account, Shannon [l] introduced local distortion measures as follows. Let the information source produce a sequence of letters {Xi} from an alphbeat Ax which is reproduced as the sequence {Xi} from an alphabet Ag. A local distortion measure of span g is then any function p9(xl,x2,. . a,.~,; R,,R,, . . .,$,) & p,&; f) of source and reproduction sequences of length g such that pg( .) 2 0. The distortion between n-tuples is then given by
TL;DR: In this paper, the authors investigated the optimality of a design with simultaneous occurrence of buckling as a wide Euler column and local buckling of the plate between the stiffeners, and the total amount of material per unit width of the panel was prescribed.
TL;DR: In this article, the dynamic mechanical response of hardened cement paste specimens as a function of the curing-heat treatment history was investigated. But the results were limited to the temperature range from −160°C to +100°C, and the results showed that both the E-modulus and the water surface area decrease as the severity of heat treatment increases.
TL;DR: In this paper, a series of cadmium buffers were used for calibration of a newly developed Cadmium Selectrode activated with CdS/Ag 2 S. The electrode exhibits Nernstian response with a sensitivity close to the theoretical limit imposed by the conditional solubility product of cadMium sulphide, i.e., the response is linear up to pCd 9 at pH 6.7 and up topCd 11 at pH 9.
TL;DR: The practical importance of bifix-free patterns is emphasized, and a systematic way of generating all such sequences and determining their number is devised.
Abstract: A bifix of an L -ary n -tuple is a sequence which is both a prefix and a suffix of that n -tuple. The practical importance of bifix-free patterns is emphasized, and we devise a systematic way of generating all such sequences and determine their number.
TL;DR: In this paper, the Mossbauer effect of aluminum was measured over the temperature range 20-642\ifmmode^\circ\else\text degree\fi{}C, using a source specimen of aluminum with $^{57}mathrm{Co}$ in solid solution.
Abstract: The M\"ossbauer effect of $^{57}\mathrm{Fe}$ in aluminum was measured over the temperature range 20-642\ifmmode^\circ\else\textdegree\fi{}C, using a source specimen of aluminum with $^{57}\mathrm{Co}$ in solid solution. The line-broadening values were converted to diffusion constants, which can be expressed by the temperature dependence $D=0.12{e}^{\frac{\ensuremath{-}(1.4\mathrm{eV})}{\mathrm{kT}}}$ ${\mathrm{cm}}^{2}$/sec. This result differs from recent diffusion-constant determinations obtained by the tracer-sectioning method, which we feel might be in error because of solution trapping. From theoretical considerations we suggest that a new expression for the correlation factor for the diffusional line broadening might be more accurate than the one used heretofore. Earlier determinations of the second-order Doppler shift were extended almost to the melting point of aluminum. The shift depends almost linearly on temperature, with the slope given by the Dulong---Petit rule for the heat capacity. From the temperature dependence of the Lamb---M\"ossbauer factor an effective Debye temperature of (210 \ifmmode\pm\else\textpm\fi{} 15)\ifmmode^\circ\else\textdegree\fi{}K was found.
TL;DR: In this article, the spectral properties of solid square planar mono-ethylenediamine halide complexes of Pd and Pt were analyzed using two C-deuterated compounds.
TL;DR: In this article, the authors studied the effect of 80 keV argon ion implantation on the dilatational moire pattern observed in interferograms and the integrated stress acting in the damaged layer as a function of the bombardment dose.
Abstract: Lateral strains induced by 80 keV argon ion implants into silicon have been studied using X-ray interferometry and X-ray diffraction topography. The stressed state is described by the expansion of a thin surface layer, and it is shown, how it will affect the dilatational moire patterns observed in the interferograms. The integrated stress acting in the damaged layer has been studied as a function of the bombardment dose. A maximum is reached at a dose of about 2×1014 ions/cm2. The maximum local stress is of the order of 1×109 dyn/cm2.
TL;DR: In this article, a review of fracture mechanics of hardened cement paste, cement mortar and concrete from the very beginning in 1929 is presented, and the application of Griffith's theory for fracture of brittle solids to heterogeneous composite cement and concrete materials is discussed.
TL;DR: The polar-orbiting satellite ESRO I/AURORAE (1968-084A) was designed to investigate auroral particles, luminosity, and associated ionospheric effects.
TL;DR: In this paper, the Lagrange formalism is used to obtain boundary conditions for the three-dimensional case of non-normal incidence of light on a crystal exhibiting spatial dispersion, where the electric field of the light wave is parallel to the plane of incidence.
Abstract: The general case of non-normal incidence of light on a crystal exhibiting spatial dispersion is treated. The light wave will in general excite two transverse and one longitudinal polariton in the crystal. Additional boundary conditions are obtained for the three-dimensional case by means of the Lagrange formalism. The Fresnel formulae for reflection and refraction are derived, and exciton spectra for CdS are computed. Additional structure in the reflection spectrum near the longitudinal resonance energy is obtained for non-normal incidence when the electric field of the light wave is parallel to the plane of incidence.
Es wird der nichtsenkrechte Einfall einer Lichtwelle auf einen Kristall mit raumlicher Dispersion behandelt. Im Kristall entstehen im allgemeinen Falle zwei transversale Polaritonen und ein longitudinales Polariton. Die zusatzlichen Grenzbedingungen im dreidimensionalen Falle werden durch Rechnung mit Lagrangeschen Funktionen erhalten. Der komplexe Reflexionskoeffizient wird abgeleitet, und die Exzitonenspektren fur CdS werden berechnet. Bei nichtsenkrechtem Einfall wird eine zusatzliche Struktur im Reflexions-spektrum in der Nahe der longitudinalen Resonanzenergie gefunden, wenn das elektrische Feld der Lichtwelle parallel zur Einfallsebene ist.
TL;DR: The actual precision achieved in routine application of the method in the analytical laboratory was in good agreement with the calculated precision, and the results are therefore well suited for statistical evaluation of differences at the ppM level in samples of biological tissue.
TL;DR: It is shown that for nonpathological channels there is a unique SWMF which minimizes the amount of intersymbol interference defined as the discrete-time analog to the rms duration of a continuous-time signal.
Abstract: A sample-whitened matched filter (SWMF) for a channel with intersymbol interference and additive white Gaussian noise is defined as a linear filter with the properties that its output samples are a sufficient statistic for the MAP estimation of the transmitted sequence and have uncorrelated noise components. These filters are shown to exist for ali realistic channels and the complete set of SWMF's for any channel is determined. It is shown that for nonpathological channels there is a unique SWMF which minimizes the amount of intersymbol interference defined as the discrete-time analog to the rms duration of a continuous-time signal. Finally, the theory is extended to more general modulation systems including pulse position modulation and frequency position modulation.
TL;DR: In this article, the authors show that the Urbach's rule in its usual form is no longer valid for measuring the absorption edge of ZnO up to 4000 cm−1 for 11 K 350 K.
Abstract: Measurements of the absorption edge of ZnO up to 4000 cm−1 for 11 K 350 K, Urbach's rule in its usual form is no longer valid.
Die langwellige Kantenabsorption nicht dotierter ZnO-Kristalle bis 4000 cm−1 im Temperaturbereich 11 bis 878 K wird mitgeteilt. Die Messungen werden mit der Urbach-Regel verglichen. Fur T 350 K) kann die Absorption nicht mehr von der Urbach-Regel in gewohnlicher Form beschrieben werden.