Showing papers by "Eindhoven University of Technology published in 1978"

Realization and stabilization of 2-d systems

Abstract: During recent years several state-space models concerning discrete 2-D systems (systems with two time parameters) have appeared in the literature. These are used, for example, in image processing. To these models are attached the names of Attasi [1], Fornasini-Marchesini [2], Givone-Roesser [3]. In this paper it is shown that all these models are special cases of a new model which is a straightforward generalization of the 1-D case. Under certain conditions the existence of a stabilizing feedback is shown. In the last part connections with [4] are made.

Phase relations in the ternary Ti-Ni-Cusystem at 800 and 870 degrees C

Abstract: We have investigated the isothermal cross sections through the ternary phase diagram Tiz.sbnd;Niz.sbnd;Cu at 800 and 870 °C by means of the diffusion couple technique. The results have been corroborated on essential points by the investigation of equilibrated alloys. Use has been made of optical, microprobe a nd X-ray analyses. The results differ from those mentioned in the literature. For two hitherto undescribed ternary intermetallic compounds X-ray diffraction data are given and crystallographic cell parameters are proposed.

On linear dynamical equations of state for isotropic media I: General formalism☆

Abstract: In this paper we investigate the relation (dynamical equation of state) among the (mechanical hydrostatic) pressure P , the volume ν and the temperature T of an isotropic medium with an arbitrary number, say n , of scalar internal degrees of freedom. It is assumed that the irreversible processes in the medium are due to volume viscosity and to changes in the internal variables and that these processes can be described with the aid of non-equilibrium thermodynamics. It is shown that an explicit form for the dynamical equation of state may be obtained if in the neighbourhood of some state of thermodynamic equilibrium it is permissible to consider the equilibrium pressure and the thermodynamic affinities (conjugate to the internal degrees of freedom) as linear functions of ν, T and the internal variables and if, moreover, the phenomenological coefficients, which occur in the equations for the irreversible processes, may be considered as constants. This dynamical equation of state has the form of a linear relation among P , ν, T , the first n derivatives with respect to time of P and of T and the first n +1 derivatives with respect to time of ν.

Generalized quadratic residue codes

Abstract: A simple definition of generalized quadratic residue codes, that is, quadratic residue codes of block length p^{m} , is given, and an account of many of their properties is presented.

Improved methods of estimating monomer reactivity ratios in copolymerization by considering experimental errors in both variables

Abstract: Existing methods of calculating monomer reactivity ratios in copolymerization are reviewed briefly, evaluated, and classified according to their mathematical and computational similarities. More attention is paid to procedures based on the integrated copolymer equation with which calculation of r values is performed most often by electronic computer. Unfortunately, until now all procedures have shown shortcomings because the real-error structure of the observations has not been taken into account. A new algorithm that does account correctly for measurement errors in both variables is described. A computational method is illustrated for copolymerization data obtained from quantitative gas chromatographic analysis of the monomer feed throughout the reaction. It is shown that the actual error structure of the variables corresponds to the assumed error structure. Reliability of the estimates is substantially increased, compared with the existing methods. Standard deviations of the monomer reactivity ratios are given and appear to be in good agreement with reality.

Analysis of symmetrical Van der Pauw structures with finite contacts

Abstract: A theory is given for Van der Pauw structures with contacts of non-zero lengths which are invariant for rotations of 90°. A general theorem has been derived. For a certain class of structures an analytical solution of the Laplace equation is obtained instead of using finite difference equations. The method leans heavily on Schwarz-Christoffel transformation techniques.

Short‐cut method for the calculation of sterilization conditions yielding optimum quality retention for conduction‐type heating of packaged foods

Abstract: Based on analytical equations for the temperature distribution history in a container, the relation between the reductions of the concentrations of heat labile food components, including microorganisms. nutrients and sensory factors, and the kinetic parameters of the reactions causing these reductions, has been calculated numerically. For a constant temperature of the heating medium with time it is concluded that the loss of quality is almost minimal at one Fourier value of the heating time. This optimal Fourier value is a function of only the Biot number and the relationship between initial product temperature, cooling water temperature and retort temperature. At an infinite value of Biot and a cooling water temperature equal to the initial product temperature the optimum Fourier value amounts to 0.5. On the basis of this conclusion a short-cut calculation method is developed. The method is valid for Biot numbers larger than 10, initial homogeneous product temperatures equal to or larger than the temperature of the cooling medium and for the main container geometries including spheres, cylinders and rectangular bodies. The method does not require tedious interpolations of tables. The calculation of the optimum process conditions to obtain the desired sterility and the calculation of the retention of the quality factor of interest require only a few minutes on a pocket calculator. For routine calculations the procedure can conveniently be programmed.

Phase diagrams of pseudo one-dimensional Heisenberg systems

Abstract: We present the first theoretical results on the anomalous field dependence of the N\'eel temperature for a system of loosely coupled classical Heisenberg chains with orthorhombic anisotropy for different directions of the applied magnetic field. The results compare favorably with the experimental phase diagrams of a series of selected $S=\frac{5}{2}$ compounds with varying degrees of one dimensionality and anisotropy.

1/ƒ Noise in solid state single injection diodes

Abstract: 1/ƒ noise calculations and experiments are presented for solid state single injection diodes operating in the ohmic and space-charge-limited current (SCLC) regime. Investigations are performed on diodes both with a planar and with a hemispherical geometry. In the ohmic regime the 1/ƒ voltage noise is proportional to the square of the bias voltage V for both geometrics. In the space-charge regime the 1/ƒ voltage noise is theoretically found to be proportional to V and V 3 4 for planar and hemispherical geometry, respectively. Here the current is proportional to V2 and V 3 2 , respectively. The experiment al results of 1/ƒ voltage noise are found to be in agreement with the calculations for both kinds of geometry.

On low-frequency noise in tunnel diodes

Abstract: A model describing the low-frequency current noise in metal-insulator-metal diodes is presented. It is assumed that the transmission coefficient is modulated by the Nyquist noise of the insulator. This coefficient in turn modulates the current. The frequency dependence of the noise is calculated to be ƒ −α , where α depends on the impedance of the insulator and can have the values 0 or 1 or 2. The model is compared with experimental results, and the agreement is found to be satisfactory.