scispace - formally typeset
Search or ask a question

Showing papers by "Technical University of Madrid published in 1983"


Journal ArticleDOI
TL;DR: In this paper, the lower stability limit for axisymmetric floating zones at rest between equal coaxial disks has been experimentally verified for several disk-separation/disk-diameter ratios by using the neutral buoyancy technique.

74 citations


Journal ArticleDOI
01 Sep 1983
TL;DR: A new configuration is therefore proposed, which includes both active and passive components, which can be used for both AC and DC convertors, especially where very low distortion is needed at the output.
Abstract: The need for output filters with static power convertors is well known. The paper presents a different way of solving the problem. A new configuration is therefore proposed, which includes both active and passive components. The advantages of this system are, among others, that it can be used for both AC and DC convertors, especially where very low distortion is needed at the output. A method for calculating the different components is proposed, and practical results obtained from a prototype are given. The possibility of using such filters with variable-frequency convertors is discussed.

26 citations


Journal ArticleDOI
TL;DR: In this article, the peak temperature in the corona of a laser-irradiated slab is discussed in terms of a one-electron-temperature model, where both heat-flux saturation and pulse rise-time effects are considered; the intensity in the rising half of the pulse is approximated by a linear function of time, I(t) ≡ I0t/τ.
Abstract: The peak temperature in the corona of plasma ejected by a laser-irradiated slab is discussed in terms of a one-electron-temperature model. Both heat-flux saturation and pulse rise-time effects are considered; the intensity in the rising half of the pulse is approximated by a linear function of time, I(t) ≡ I0t/τ. The temperature is found to be proportional to (I0λ2)2/3 and a function of I0λ4/τ. Above a certain value of I0λ4/τ, the plasma presents two characteristic temperatures (at saturation and at the critical surface) which can be identified with experimentally observed cold- and hot-electron temperatures. The results are compared with extensive experimental data available for both Nd and CO2 lasers, I0(Wcm−2) λ2 (μm) starting around 1012. The agreement is good if substantial flux inhibition is assumed (flux-limit factor f 0.03), and fails for I0λ2 above 1O15. Results for both ablation pressure and mass ablation rate are also given.

19 citations


Journal ArticleDOI
TL;DR: In this article, the authors derived the rules for increasing the energy cast on the concentrator's collector and figures of merit are proposed for concentrators working under these conditions, and applied them to several specific static concentrators illuminated by the time-averaged sky radiance of Madrid.

14 citations


Journal ArticleDOI
TL;DR: In this article, the authors measured the energy of Bloch's walls in amorphous ferromagnetic ribbons using a method devised by R. Aleonard et al. to induce uni-directional anysotropy in the samples using stress.

14 citations


Journal ArticleDOI
TL;DR: This paper presents a method for designing ideal and optimal 2-D concentrators when the collector is placed inside a dielectric tube for the particular case of a bifacial collector, based on the extreme ray principle of design.
Abstract: In this paper we present a method for designing ideal and optimal 2-D concentrators when the collector is placed inside a dielectric tube for the particular case of a bifacial collector. The method, based on the extreme ray principle of design, avoids the use of differential equations by means of a proper application of Fermat's principle. One advantage of these concentrators is that they allow the size to be small compared with classical CPCs.

14 citations


Journal ArticleDOI
TL;DR: In this article, les auteurs donnent la distribution de sept especes de Taeniopterygidae dans trente-neuf stations situees sur le Duero et ses affluents.
Abstract: Les auteurs donnent la distribution de sept especes de Taeniopterygidae dans trente-neuf stations situees sur le Duero et ses affluents. Ils decrivent Brachytera vera nov. sp. et discutent des caracteres specifiques de quelques autres Brachypterinae.

6 citations


Journal ArticleDOI
TL;DR: In this article, the currentvoltage characteristics of p+-i-n+solar cells are analyzed and an approximated two-exponential model for the dark and J-sc-Voc operation is presented.
Abstract: The current-voltage characteristics of p+-i-n+solar cells is analyzed and an approximated two-exponential model for the dark and J_{sc}-V_{oc} operation is presented. It is shown that this two-exponential model and the superposition principle can be used as a first approximation and as a means of attaining further insight on the basic mechanisms actually occurring in the cell. However, some care should be taken when trying to determine the physical solar cell parameters from experimental data through fitting techniques. All this facts are illustrated and confirmed with theoretical examples and measured current-voltage characteristics of six different devices.

4 citations


Journal ArticleDOI
TL;DR: In this article, the thermal decomposition in air of several complexes of chromium(III) with imidazole, N-methylimidazoles, and 2-Methylimideazole has been studied with the aid of differential thermal analysis (DTA), thermogravimetry (TG), and derivative thermograves (DTG) in the temperature range 25-600°C.
Abstract: The thermal decomposition in air of several complexes of chromium(III) with imidazole,N-methylimidazole and 2-methylimidazole has been studied with the aid of differential thermal analysis (DTA), thermogravimetry (TG) and derivative thermogravimetry (DTG) in the temperature range 25–600°C. Although the final process of the decomposition gives Cr2O3, there are interesting differences in the complete process of decomposition. The reasons for these differences appear to be related to the trans-effect and to the presence in the imidazole complexes of hydrogen bonds. Enthalpies of the several decomposition reactions have been determined by differential thermal analysis.

4 citations


Journal ArticleDOI
TL;DR: In this article, a new type of domain for nematic liquid crystals with a twisted-wedge structure is presented from the low frequency range to 10 kHz, which offers a higher degree of complexity than conventional Williams domains.
Abstract: A new type of domain for nematic liquid crystals with a twisted-wedge structure is presented. This new type of domain appears from the low frequency range to 10 kHz. This behavior was observed for square and pulsed excitations. The liquid crystal was N-(p-methoxybenzylidene)-p'-butylaniline) (MBBA) used at room temperature. These domains offer a higher degree of complexity than conventional Williams domains. The corresponding stability chart is presented.

2 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present a computer calculation method which permits the determination of the elevation angle with respect to the equator for each position adopted by a quasi-static collector, and also the calculation of the minimum collector area to be installed to achieve the maximum agreement between the curves of energy needed and collected with no seasonal accumulation.


Journal ArticleDOI
TL;DR: A didactic microcomputer designed and built by the authors to teach microcomputer architecture in the secondary education, the MICROSIMPLEX is useful for students in an advanced phase to learn how to build systems based on microprocessors by using connectable parts.

Journal ArticleDOI
TL;DR: In this paper, a microprocessor based control circuit using the MC6802, which generates all the control signals necessary for feeding AC motors, is presented, based on the Control Rose Theory and the Existential Function Modulation (E.F.M).

Journal ArticleDOI
TL;DR: In this paper, the Electronic Engineering Department of the Industrial Engineering College of Madrid developed an equipment which, in its prototype stage, has allowed a study to be made of the possibilities of connecting photovoltaic arrays to the electric power mains through a suitable high power circuit.

Journal ArticleDOI
TL;DR: This paper studies the static allocation in a computer network of a tasks set with arbitrary and deterministic precedence constraints, in order to optimize the total processing time.

Journal ArticleDOI
TL;DR: It is shown that this function can be interpretated as the result of the interaction between the seasonal and regular autocorrelation patterns of the ARMA model, which makes easier the identification of the structure of the model and is helpful in choosing between a multiplicative or additive seasonal component.
Abstract: : This note obtains the theoretical autocorrelation function of an Autoregressive Moving Average (ARMA) model with multiplicative seasonality. It is shown that this function can be interpretated as the result of the interaction between the seasonal and regular autocorrelation patterns of the ARMA model. The use of this result makes easier the identification of the structure of the model, is helpful in choosing between a multiplicative or additive seasonal component and leads to a better understanding of the properties of the estimated autocorrelation function of scalar ARMA processes. (Author)

Book ChapterDOI
01 Jan 1983
TL;DR: In this article, the authors present a review of the problems involved in the design of an automatic planner system, and the attention is focused in the particular problems that appear when the planner is used to control the actions of a robot.
Abstract: After a brief review of the problems involved in the design of an automatic planner system, the attention is focused in the particular problems that appear when the planner is used to control the actions of a robot. As conclusion, the introduction of techniques for learning in order to improve the efficiency of a planner are suggested, and a method for it, at present in development, is presented.

Journal ArticleDOI
TL;DR: In this paper, a large record series was used for the identification of a support system in a mine, where roof blasting was performed in the lab of the Laboratorio Oficial Jose Maria Madariaga.

Book ChapterDOI
01 Jan 1983
TL;DR: The package performs the following tasks: calculation of the equivalent z-transfer function of a continuous system, stability design; interaction improvement; operations with transfer functions matrices and simulation of closed loop discrete multivariable systems.
Abstract: In this paper, a package of programs for the computer aided design of discrete multivariable linear control systems is shown. It is based on frequency-domain techniques. Also, a new stability design method for multivariable systems is described. The package performs the following tasks: calculation of the equivalent z-transfer function of a continuous system, stability design; interaction improvement; operations with transfer functions matrices and simulation of closed loop discrete multivariable systems. The solution of these tasks leads to the manipulation of transfer functions matrices. It is carried out with the aid of the Graph Theory. A design example is included to illustrate the use of the stability design method and the efectiveness of the package.

Book ChapterDOI
01 Jan 1983
TL;DR: In this paper, a new method to calculate the cartesian trajectories of the gripper that manipulates the pieces with special velocity and acceleration conditions is presented. But the problem is not addressed in this paper.
Abstract: Industrial robots, nowadays, are being introduced in the advanced manufacturing system where it is usually needed to manipulate or trans port moving objects to different destinations, tipically machine tools with numeric control, stationary or moving devices or storages. With the help of a TV sensor system it is possible to compute the position and orientation of the moving workpieces. This paper deals with a new method to calculate the cartesian trajectories of the robot's gripper that manipulates the pieces with special velocity and acceleration conditions. Parameters of trajectories are calculated with a minimum time criterion. The present algorithm verifies, by means a fast method, if the calculated trajectory is in the working-area of the robot. Also real-time reference inputs of the servomechanism of the robots links are generated. A crucial problem treated in this paper is the arrangement of grasping in the case of several moving objects. A tree data organization is used with a special tree search algorithm. The first available solution, if it exists, is computed within an admissible execution time. Algorithms have been simulated in a minicomputer and later have been implemented with two microprocessors with hierarchical structure controlling a manipulator developed in our Departament.

Journal ArticleDOI
TL;DR: In this article, a novel technique based on pulse electroplating and surface treatment with very slow etching rate solutions has been applied to fabricate Au Schottky barriers on GaAs 1-x P x and Ga1-xAlxAs.
Abstract: A novel technique based on pulse electroplating and surface treatment with very slow etching rate solutions has been applied to fabricate Au Schottky barriers on GaAs 1-x P x and Ga1-xAlxAs. Device characteristics are compared to the behaviour of vacuum-deposited barriers. The present technique allows a simple and fast procedure to obtain Schottky barriers for material evaluation and device applications.