Observations of Quasi-Periodic Electric Field Disturbances in the E Region before and during the Equatorial Plasma Bubble

Wave-like electric field disturbances in the ionosphere before the Equatorial Plasma Bubble (EPB) are the subject of numerous recent studies that address the issue of possible short-term forecasting of EPB. We report the observations of the Equatorial Quasi-Periodic-Electric field Disturbances (QP-EDs) of the Field-aligned Irregularities (FAI) in the E region before the EPB occurrence in the F region. They are observed from 30 MHz coherent scatter radar during the SpreadFEx campaign 2005 carried out in Brasil. The presently reported QP-EDs at the equatorial E region below an altitude of 110 km are undescribed so far. Though QP-EDs characteristics vary on a day-to-day basis, consistent features are their intensification before the EPB, and their simultaneous occurrence with EPBs. This study highlights the monitoring of QP-EDs in the short-term forecasting of EPBs and further reveals the robust energetics of vertical coupling between E and F regions.

RESONANCE AS NEW METHOD IN DETERMINING THE AGE OF PAINTS

In this work the mechanism of resonance is proposed as the way for determining of paint age, by application of this method. This method consists in accelerated paint ageing on the basis of resonance. Measuring is concerned with humidity of paint and it is a general method since water molecules are present in every material. The molecules of water have random distribution. They oscillate in shallow potential wells so that they can be ejected from paint with low energy quanta, thus decreasing the paint humidity by evaporation process. The high energy quanta accelerate this process of the paint ageing. Since water molecule is mechanical oscillator it can be turned into resonance by application of mechanical periodical field, but since it is electric dipole it can be even more conveniently turned into resonance with periodic electric field.

Electrically Tunable Diffraction Grating Based on Liquid Crystals

A periodic electric field is generated in the grating-like electrodes cell by an applied voltage and results in the reorientation of liquid crystals. The linearly polarized probe beam experienced periodic distribution of refractive index and formed a phase grating. He-Ne laser was used as the probe beam to detect the zeroth-order (o) and first-order (+1) diffraction intensities. The experimental results showed that the diffraction grating can be switched on by applying a small voltage. The optimal first-order diffraction efficiency is about 12%. The dependence of the first-order diffraction efficiency on the polarization of the probed beam is also discussed herein.