Revista Cubana de Física

In the Experiment Manual of the Computer Aided Physics Laboratory System HPCI-1 of U-Star Sensor Technology Co., Ltd from Chine are included some experiments dedicated to the study of AC circuits. Among them there is one dedicated to determine qualitatively the phase shift between current and voltage in the RC circuit with resistance changes. Using the circuit and the specific software for this experiment and another circuit of the system for other experiment were designed three lab practices for determine quantitatively the changes of phase shift between current and voltage in the RC and RL circuits with resistance change and how this phase shift behaves in a RLC circuit when it is predominantly capacitive, inductive or it is in resonance condition. A proposal of a lab practice that includes the study of the three circuits was done.

The main point of this study is to determine when and where proton emission and β+-decay happen. The study focused on the three factors, the Coulomb effect, a core deformation, and the clustering configurations. In this work it was used the Microscopic Cluster Model to describe the system. The description of any system that will fragment by clustering forms has been considered in order to expand this methodology to all radioactive nuclei. The results confirmed this logical description and support its use for all radioactive isotopes. The 1_7_Ne has been investigated within this work.

Using the possibilities of experiment “Isochronism of Simple Pendulum” of the Computer Aided Physics Laboratory HPCI-1, the records of the variations of the electric voltage with time corresponding to the angular positions of the integrating bodies of three simple pendula in small oscillations with different masses were obtained. Applying the Analyze tool of the HPCI-1 the values of the amplitudes in the different instants of time were obtained and later processed using EXCEL. In this way, a general study of the damped oscillations of this system was carried out. With the used variant, the laboratory work goes beyond the traditional study restricted to harmonic oscillations without the presence of friction forces, situation that does not correspond with the real pendulum one. In particular, the damping coefficients of the spheres for the air were obtained and the influence of the mass of the bodies on them was evidenced, also their influence in amplitude and frequency of oscillations was shown.

Nowadays, there is consensus about the relevance of lead-free piezoceramics. In this work KNNLiLaTa0.1 ceramics fulfilling that requisite were obtained using NaNbO3 as precursor. By means of SEM, NaNbO3 showed a grain morphology consisting in thin rectangular platelets. However, in KNNLiLaTa0.1 the grains were polyhedral, with dimensions much smaller than those of the precursor grains, showing a bimodal distribution due to the presence of some dopants, like lanthanum.

The hyper-Rayleigh scattering first hyperpolarizabilities βHRS of a series of push-pull oligomer are studied using theoretical chemistry methods. Several DFT XC functionals have been used while reliable atomic basis sets have been selected for their evaluations. The behavior of hyper-Rayleigh scattering first hyperpolarizability is studied as a function the basis sets, of electron correlation, of solvent as well as the strength of the electron donor groups to address structure-property relationships.  It has been observed that the electron correlation effects are huge, the Møller–Plesset results reproduces the values of the first hyperpolarizability obtained with the reference CCSD(T) level. Among density functional theory exchange-correlation functionals, B3LYP, M062X and CAM-B3LYP are reliable to the MP2 characterized static and dynamic first hyperpolarizability. Finally, the EFISHG first hyperpolarizabilities values put on view different ordering and present more delicate variations as a function of the substituted oligomers. The depolarization ratios follow an opposite ordering as the anisotropy factors while they display an extensive separation dipolar-octupolar character.