Mircea Preda

New Liquid-Membrane Electrodes used for the Determination of Copper and Nickel

Abstract Four electrodes with a liquid membrane, Cu−2 -selective and Ni2+ -selective, respectively, not described previously in the literature, were prepared and characterized. From these electrodes 1 and 2 are based on simple complexes of Cu(II) and Ni(II) with 6-nitro-quinoxaline-2,3-dithiol (6 - nitro - Q.D.T.) as ligand. Electrodes 3 and 4 are based on the corresponding mixed complexes in which the ammonia molecule acts as the second ligand along with 6-nitro-quinoxaline-2,3-dithiol as the first ligand. Both the Cu2+ -selective electrode and Ni2+ -selective electrode have been used to determine the Cu2+ and Ni2+ ions in aqueous solution both by direct potentiometry and by potentiometric titration with EDTA. The primary and secondary characteristics of these electrodes, as well as their selectivity constants for practical use in the potentiometric assay of copper and nickel, were determined. By comparison with the electrodes based on the simple complexes (1 and 2) the electrodes based on mixed complexe...

Data Requirements for Detecting Student Learning Style in an AEHS

According to educational psychologists, the efficiency and effectiveness of the instruction process are influenced by the learning style of the student. This paper introduces an approach which integrates the most relevant characteristics from several learning style models proposed in the literature. The paper’s focus is on the data requirements for the dynamic learner modeling method, i.e., the learner’s observable behavior in an educational hypermedia system; based on the interpretation of these observables, the system can identify various learning preferences.

Adaptive Learning Based on Exercises Fitness Degree

The paper considers the e-learning systems that provide personalized content to their users and that permanently adapt to the evolution of the users during their learning stages. Such systems help the students to consolidate their knowledge faster than other methods. The main contribution is the proposal of a mathematical model of an adaptive learning system with the mentioned characteristics. The model involves a multi step process where, at each stage, the performances of the student are measured and the system is adapting accordingly.