Modeling power supplies of LED lamps

In the paper, the model of the power supply of the LED lamp in the form dedicated for SPICE is proposed. The form of the worked out by the authors' model is presented, and the results of experimental verification of this model for the LED lamp of the type CLA25 are shown. The presented model is elaborated only for the power supply of LED lamps, in which the constant output voltage is stabilized. This model has the form of a subcircuit for SPICE, and it describes the influence of load resistance, amplitude of the input voltage, and the ambient temperature on both the input current and the output voltage. It is confirmed that the worked out model describes correctly both the waveform of the current received from the electroenergy network and the influence of the load current, the ambient temperature, and the supply voltage on the output voltage.     

Remanence and switching sensitivity in nanodot magnetic arrays

New results are reported of the computer simulations on the magnetic behaviour of magnetic arrays of nanoscopic dots, placed in cells of the square lattice. We show that the remanence magnetization M(r) decreases with the array size. For arrays 50 x 50, we investigate also the stability of the magnetic structure of an array in an oscillating magnetic field. The damage spreading technique reveals that this stability increases with the standard deviation sigma of the switching field of individual elements of the array. On the other hand, M(r) decreases with sigma. An optimalization of the system (large M(r) and large stability) can then be reached at some intermediate value of sigma.     

Hydrophobization of Lime Composites with Lignocellulosic Raw Materials from Flax

The aim of the study was to evaluate the possibility of applying lime binder together with flax fibers and straw to the production of wall materials. Properties of the composites were modified by additives and admixtures. The following laboratory tests were performed: the analysis of the physical characteristics, compressive strength, a water droplet absorption test, water absorption of hydrophobized and standard samples, drying time, and analysis of the structure using scanning electron microscope (SEM). In the paper, there was examined the effectiveness of two formulations differing in the degree of hydrolytic polycondensation, viscosity, and concentration, as these are the factors that determine the final impregnation effect.     

Oversampling ΣΔ Analog-to-Digital Converters Modeling Based on VHDL

The paper presents a VHDL model of an oversampling analog-to-digital converter created on the behavioral hierarchy level. Although VHDL has been primarily devoted to digital circuit design, it can also be applied to certain mixed-signal circuits. The model of the analog part is as simple as possible and includes only necessary parameters that enable to determine the potential resolution of a converter. The model of the digital part is described in the synthesizable subset of VHDL and parameterized according to the word length and the type of arithmetic applied. The validation process of the converter model is also shown. It is performed by a VHDL simulator and a postprocessor tool enabling to carry out FFT. Simulation results enclosed prove the efficiency of the design approach presented.     

Kendall’s correlation coefficient for vague preferences

The problem of measuring association between preference systems in situations with missing information or noncomparable outputs is discussed. New correlation coefficient, which generalizes Kendall’s correlation coefficients used traditionally in statistics, is suggested. The construction utilizes IF-sets.     

Time,Budget, And Functionality?—IT Project Success Criteria Revised

The purpose of this article is to explore the relevance of classic project success measures of Enterprise Systems implementation projects' success from the adopting organizations' perspective. Based on a mixed quantitative-qualitative approach, the results show that, although the organizations valued project management criteria, they did not perceive them as determinants of success if the goals of the project were achieved. A refined set of success criteria is proposed on the basis of these findings.     

The mathematical models of kinetics of the E, EC, ECE, ECEC, ECE-ECE and ECEC-ECEC processes with potential-dependent transfer coefficient as a rationale of isoalpha points

It has been proven that including elementary potential-dependent transfer coefficient (α) into mathematical model of E, EC, ECE, ECEC, ECE-ECE and ECEC-ECEC mechanisms leads to creation of set of cyclic voltammetry curves with the intersection point called isoalpha point. The isoalpha points have been detected by the use of the models of particular mechanisms with and without ∂α/∂E parameter included or through different alpha values introduction. The point of intersection unknown in electrode kinetics so far, seems to exemplify an electrochemical analog of isosbestic point in absorption spectroscopy or isopotential point in electrochemistry. Moreover, an example of the experimental data that demonstrates the presence of the isoalpha point has been provided. The presented phenomenon can be of importance for solid state and modified electrodes.