Showing papers by "Eindhoven University of Technology published in 1975"

Approximate equations for long water waves

Abstract: In the first part of this paper the Hamiltonian theory of water waves is used to obtain some equations in local coordinates. These equations are approximations of the Boussinesq type. They are stable with respect to short wave perturbations, e.g. rounding off errors in digital computing. In the second part the relation of Boussinesq equations to Korteweg-de Vries and Benjamin-Bona-Mahony equations is investigated.

Erosion and the origin of charged and neutral species in vacuum arcs

Abstract: Erosion measurements on copper cathodes show the erosion rate to be dependent on different variables, such as arc current, arcing time and cathode size. The experimental results offer an explanation of the large variation in erosion rate values as found by earlier experiments. The behavior of other cathode metals proves to be similar. An analysis shows the variation in erosion to be caused by changes in the output of neutral species. It is concluded that ions and neutrals differ in origin of generation, the cathode spots being the centres of fully ionized metal vapour, while neutrals are formed in surrounding areas.

An Optimum Linear Receiver for Multiple Channel Digital Transmission Systems

Abstract: An optimum linear receiver for multiple channel digital transmission systems is developed for the minimum P e and for the zero-forcing criterion. A multidimensional Nyquist criterion is defined together with a theorem on the optimality of a finite lenght multiple tapped delay line. Furthermore an algorithm is given to calculate the tap settings of this multiple tapped delay line. This algorithm simplifies in those cases where the noise is so small that it can be neglected. Finally as an example the transmission of binary data over a cable, consisting of four identical wires, symmetrically situated inside a cylindrical shield, is considered.

Distinguishable- and indistinguishable-particle descriptions of systems of identical particles

Abstract: The problem of distinguishability of identical particles is considered from both experimental and theoretical points of view. It is argued that distinguishability has to be defined relative to a definite set of experiments and that the criterion by which the particles are distinguished should be specified. Failure to do so may cause mismatching between theory and experiment. On the theoretical level a distinction is made between indexed- and unindexed-particle theories, indices being unobserved intrinsic properties of the particles. A field theory of indexed particles is constructed and shown to be equivalent to the second quantization formalism, which is an unindexed-particle theory.

Specific heat of nearly-one-dimensional tetramethyl ammonium manganese trichloride (TMMC) and tetramethyl ammonium cadmium trichloride (TMCC)

Abstract: The specific heat of tetramethyl ammonium manganese trichloride and its cadmium isomorph is measured for $2lTl52$ K. The temperature dependence of the lattice specific heat of the cadmium compound could be fitted with an expression based upon a pseudoelastic approach of the lattice vibrations in this low-dimensional system. Application of this approach to the manganese compound yields a magnetic contribution which fits the overall behavior of a one-dimensional Heisenberg model with an intrachain interaction of $\frac{J}{k}=\ensuremath{-}6.7\ifmmode\pm\else\textpm\fi{}0.5$ K. Inspection of the low-temperature region yields a satisfactory agreement with the expression ${C}_{m}=1.1|\frac{\mathrm{kT}}{J}|+0.5{|\frac{\mathrm{kT}}{J}|}^{2}\ensuremath{-}0.13{|\frac{\mathrm{kT}}{J}|}^{3}$, predicted by recent calculations.

Discounted semi-Markov decision processes : linear programming and policy iteration

Abstract: For semi-Markov decision processes with discounted rewards we derive the well known results regarding the structure of optimal strategies (nonrandomized, stationary Markov strategies) and the standard algorithms (linear programming, policy iteration). Our analysis is completely based on a primal linear programming formulation of the problem.

On Markov games

Abstract: In the paper it is demonstrated, how a dynamic programming approach may be useful for the analysis of Markov games. Markov games with finitely many stages are dealt with extensively. The existence of optimal Markov strategies is proven for finite stage Markov games using a shortcut of a proof by Derman for the analogous result for Markov decision processes. For Markov games with a countably infinite number of stages some results are summarized. Here again the results and the methods of prove have much in common with results and proofs for Markov decision processes. Actually the theory of Markov games is a generalisation. The paper contains short introductions into the theories of matrix games and tree games.

Digital Simulation of the Steady State Behaviour of Moving Bed Processes

Abstract: A mathematical description of a complicated pellet indurating machine is presented that is simple and useful for digital computation and optimisation purposes. The arguments for some of the approximations used are given together with the resulting differential equations. A short discussion is devoted to some of the computational aspects.The verification of the model is described briefly, and typical computational results are presented from which some process conclusions are drawn.Although the process is specialised, the approach followed in this paper may be useful to other types of packed bed processes including sintering and drying of foods.

Detection of 20 Na atoms and measurement of sodium-vapor densities by means of atomic-resonance fluorescence

Abstract: The method of atomic-resonance fluorescence has been applied to the detection of very small concentrations of radioactive 20Na atoms (<3 × 109 m−3). The 20Na isotope is produced by the reaction 20Ne(p, n)20Na by passing a 20 MeV proton beam through a neon gas target of density 3.5 × 1024 atoms/m3. A beam of a continuous-wave dye laser tuned to the D2 line of sodium is transmitted through the production region and the fluorescence light is detected by means of photon counting. A digital synchronous-detection technique has been applied to measure the time-dependent behavior of the 20Na atom density shortly after a proton irradiation. This behavior is determined both by radioactive decay and by diffusion of the atoms out of the production region. The absolute 20Na atom density has been estimated, using Rayleigh scattering of the laser beam on the neon gas for calibration of the optical system. The density of neutral 20Na atoms appeared to be an order of magnitude lower than the density produced. The detection method has also been used to measure the temperature dependence of saturated sodium-vapor density down to 3 × 1011 atoms/m3 (292 K).

Permeability and preparation of micropacked columns

Abstract: A simple procedure for preparing packed columns with an internal diameter of 0.6–0.8 mm and up to 15 m long is described. Theoretical plate numbers of the order 40,000 at capacity ratios >4 can be obtained at moderate inlet pressures. Special attention is given to the permeability of packed capillaries and micropacked columns. Some examples are given of separations obtained with micropacked columns.

Hidden hamiltonians of first-order equations

Abstract: There are equations, like the KDV equation, of which the solutions behave like conservative systems although the equation is of first order in time. It is shown how equations of this kind can originate by a direct-product like process of fusion of two canonical conjugate variables. Conversely, for a class of dynamically well-behaved first-order equations a splitting of the independent variable into two conjugate parts and a corresponding hamiltonian functional can be found. It is shown how the action principle and the Noether theorem transform during this fusion or splitting process. A number of examples are discussed. It is shown how a KDV approximation can be derived directly from the hamiltonian of a second-order system without using the second-order wave equations.

The uptake and elimination of halothane in dogs: a two or multicompartment system? ii: evaluation of wash-in and wash-out curves

Abstract: In 14 mongrel dogs wash-in and wash-out curves for halothane were obtained from measurements of arterial blood, mixed venous blood and end-tidal gas. From a certain point in the wash-in period the halothane concentration of arterial blood can be calculated from the halothane concentration in end-tidal gas and the blood-gas partition coefficient for halothane. Analysis of the curves shows that they are composed of two exponential components suggesting the presence of two body compartments. The question of a two-compartment system versus a multi-compartment system is discussed.

Measurement of the diffusion coefficient of sodium vapour in neon gas at 300 K

Abstract: The diffusion coefficient of sodium in neon has been measured at 300 K. In a cylindrical cell filled with 3.5 × 1024 atoms/m3 neon, the radioactive 20Na isotope is produced by means of a short irradiation of 20 MeV protons. Starting 40 ms after the irradiation, the decrease in the 20Na atom density at several positions in the cell was measured using the resonance fluorescence technique, The decrease is determined both by radioactive decay and by diffusion of the atoms to the wall. The diffusion has been simulated by a numerical model. From comparison of the experimental with the numerical results the diffusion coefficient D of 20Na atoms in neon is obtained. The value of D found is (35 ± 8) × 10-6 m2/s at 1 atm and 300 K.

Direct sample introduction of high boiling compounds onto glass capillary columns. Comparison of manual and automatic sampling

Abstract: The performances of two systems for the direct introduction of high boiling compounds onto glass capillary columns are compared. Samples investigated consisted of hydrocarbons and steroids. The “Moving Needle” system (a manual version) developed in our laboratory is extensively described in the literature [1]. The standard deviation for quantitative measurements is approximately 2.5% rel. Recently a Pye Auto Solids Injector has been modified so as to meet the requirements set by capillary gas chromatography. The very large dead volume of this sampling system, due to the use of sample holders prevents the direct coupling of this system to a capillary column. After introduction of a sample holder the solid sample evaporates slowly and the sample compounds are spread throughout a large volume of carrier gas, this badly affects the resolution obtainable. To overcome this problem the oven of the chromatograph contains a capillary precolumn (of some 50 cm length), which during a short period after sample introduction is cooled by a flow of air. During this cooling period the sample compounds are effectively trapped in the pre-column. After one minute the cooling medium is turned off, the pre-column rapidly heats in the column oven and a sharp reinjection of the sample occurs. A complete description of the system is given. The repeatability of quantitative measurements {σrel} is better than 1.5%. There is no loss of resolution by using this sampling technique. Both systems described are compatible with isothermal and programmed operation. Also in both versions the solvent does not enter the capillary column to an appreciable extent.

Computer Calculations of the Chemical Transport of GaSe in Closed Tubes

Abstract: Chemical transport of the system GaSe-Iodine in closed tubes is studied theoretically. The published GaSe heat of formation was halved to get a good agreement between the theory and experiments leading to a conclusion that the existing form of gallium selenide is Ga2Se2. The calculation shows the transport of gallium selenide to be controlled by diffusion and laminar flow of the subliming gallium selenide in the region of low iodine concentrations, while in the highiodine concentration region, the thermal convection combined with the disproportionationreaction plays an important role in transport in addition to the diffusion and the laminar flow.

INDO calculations on the sigmatropic [1,5] H-shift in 1,3-cyclohexadiene and 1,3,5-cycloheptatriene : a homo-cyclopentadienyl transition state model

Abstract: INDO calculations have been performed for the activated complex of the [1, 5] H.-shift in 1,3-cyclohexadiene and 1,3,5-cycloheptatriene. During the migration in the cyclohexadiene system a homoconjugation was calculated between the carbon atoms C1 and C5.

FORMASY : forecasting and recruitment in manpower systems

Abstract: In this paper the tools are developed for forecasting and recruitment planning in a graded manpower system. Basic features of the presented approach are: - the system contains several grades or job categories in which the employees stay for a certain time before being promoted or leaving the system, - promotability and leaving rate for any employee depend on time spent in the job category and personal qualifications (like education, experience, age), - recruitment is not necessarily restricted to the lowest level ln the system, - several planning aims and restrictions are allowed. The approach is based on a generalized Markov model for the dynamic behaviour of an individual employee. On this Markov model a forecasting procedure and a recruitment-scheduling procedure are based.