Features of the photoconductivity of iodine-doped cotton fibers illuminated in the fundamental absorption range

The photoelectric properties of cotton fibers treated with iodine were studied in the fundamental absorption range. The samples exhibit a sublinear illumination-current characteristic and a long-term relaxation of photoconductivity (PC) after UV irradiation (hν=5 eV) of the iodine-doped fibers. A PC mechanism is proposed which explains both the nonlinear variation of photocurrent with illumination intensity and the PC decay according to a bimolecular recombination law after UV irradiation of the iodine-doped fiber in the fundamental absorption range.     

On Singularities of the Physical Fields at the Edge of a Composite Wedge

We propose analytic procedures capable of evaluation of the orders of power singularities of magnetic fields at the edge of a composite ferromagnetic wedge bordering with a vacuum. The same procedure is used to study the singularities at the edge of a composite piezoceramic wedge. As a result, we present the plots characterizing the dependences of the order of singularities on the wedge angles of the wedges used to form the analyzed composite wedge and the combination of their physical parameters.     

Asymptotic stabilization of some equilibria of an underactuated underwater vehicle

The stabilization problem for selected relative equilibria of an underactuated rigid body, modelling a simple underwater vehicle, moving in an ideal fluid is addressed. State feedback control laws achieving local asymptotic stability of a forward motion and of a diving/rising with forward/reverse motion are proposed. The control design exploits the Hamiltonian nature of the system to be controlled and it is based on the so-called interconnection and damping assignment (IDA) procedure. Simulation results complete the work.     

The Scientific Research Seminar on Computer Algebra in 2000–2001

An annual report on meetings of the scientific research seminar on computer algebra is presented.     

Probabilistic optimality in long-term energy sales

This paper introduces a graphic methodology that makes it possible to compare over a wide range of probabilities the revenues that a generator obtains using different policies to decide how much energy to sell under long-term contracts and how much on the spot market. Examples are based on results for the Colombian Power System     

Sensitivity of transformer's hottest-spot and equivalent aging to selected parameters

In 1995, IEEE released a revised Transformer Loading Guide which includes an Annex G that contains an additional set of transformer temperature equations that incorporate oil-flow phenomena, changing ambient air temperature, and account for the change in resistivity of the winding due to heating. These new equations involve empirical exponent variables that account for properties of the transformer. This paper investigates sensitivity of hottest-spot temperature and equivalent aging of transformers with respect to these variables. By varying these variables under various load conditions and by Monte Carlo simulation with different probability distributions of these variables, their importance in the transformer model and their influence in modeling accuracy pertaining to the Annex G equations have been obtained.     

Approximate channel identification via δ‐signed correlation

A method of approximate channel identification is proposed that is based on a simplification of the correlation estimator. Despite the numerical simplification (no multiplications or additions are required, only comparisons and an accumulator), the performance of the proposed estimator is not significantly worse than that of the standard correlation estimator. A free (user selectable) parameter moves ‘smoothly’ from a situation with small sum‐squared channel estimation error but hard‐to‐identify channel peaks, to one with a larger sum‐squared estimation error but easy‐to‐identify channel peaks. The proposed estimator is shown to be biased and its behaviour is analysed in a number of situations. Applications of the proposed estimator to sparsity detection, symbol timing recovery and to the initialization of blind equalizers are suggested. Copyright © 2002 John Wiley & Sons, Ltd.     

Optimal Massing Liquid Volume Determination by Energy Consumption Measurement: Study of the Influence of Some Physical Properties of Solvents and Products Used

This study tried to investigate, by the power comsumption technique, the influence of the powder's and solvent's properties on wet granulation.

It could be shown that the required amount of granulation liquid decreases when the particle size of the powder to be granulated increases. This relationship is however only true when the particle size distribution of the powder to be granulated is rather narrow.

Powders having the same solubility in different solvents require the same optimal liquid quantity for granulation, but the properties of resulting granules depend on surface tension and wetting properties of the solvent.

When the powder to be granulated contains crystallisation water, the temperature rising in the mixer can be sufficient to liberate this water, which must be taken into account in the optimal granulation liquid requirement.

The effect of a macromolecular binder (PVP, HPMC) has also been studied: the optimal liquid quantity required changes with the kind of binder used and the manufacturing process (binder used in solution or added as dry powder).

It was also shown that in the case of lactose, the optimal quantity of PVP or HPMC can be determined from the power consumption records and from the granules friability studies