OPTIMIZATION-BASED RECURSIVE FILTERING FOR VIBROSEIS HARMONIC NOISE ELIMINATION

The vibroseis sources always produce harmonics, which are considered here as noise to be eliminated. An algorithm for removing such noise has been developed based on the previously obtained mathematical model of a vibroseis wavelet distorted by the harmonics. It is shown that the ideal inversion operator is recursive, i.e. is a filter with infinite impulse response. However, due to the peculiarity of the problem, this operator is successfully approximated by a filter with a short impulse response, allowing linearization of the optimization scheme. An objective being the energy of the noise attenuation result is formed. It allows application of the geometrical divergence correction despite the fact that it introduces distortions in the signal shape and the harmonics.

Effect of Work Intensity on Time Delay in Mediation of Ventilation by Arterial Carbon Dioxide During Recovery From Impulse Exercise

Time delay in the mediation of ventilation (VE) by arterial CO2 pressure (PaCO2) was studied during recovery from short impulse-like exercises with different work loads of recovery. Subjects performed two tests including 10-s impulse like exercise with work load of 200 watts and 15-min recovery with 25 watts in test one and 50 watts in test two. VE, end tidal CO2 pressure (PETCO2) and heart rate (HR) were measured continuously during rest, warming up, exercise and recovery. PaCO2 was estimated from PETCO2 and tidal volume (VT). Results showed that predicted arterial CO2 pressure (PaCO2 pre) increased during recovery in both tests. In both tests, VE increased and peaked at the end of exercise. VE decreased in the first few seconds of recovery but started to increase again. The highest correlation coefficient between PaCO2 pre and VE was obtained in the time delay of 7 s (r=0.854) in test one and in time delays of 6 s (r=0.451) and 31 s (r=0.567) in test two. HR was significantly higher in test two than in test one. These results indicate that PaCO2 pre drives VE with a time delay and that higher work intensity induces a shorter time delay.

Laser Cold Ablation as a Cutting Edge Method of Forming Silicon Wafers Used in Solar Cells

The article shows experimental results of mild cutting of surface layers of polycrystalline silicon photovoltaic cells with a picoseconds UV laser. Current technology makes a strong point on reliability and quality of photovoltaic microprocessing. Using short impulse lasers guarantee best quality of cutting edge without burr, HAZ and changing crystalline structure of the base material, with is very important due to electrical conductivity of the solar cell.

Development of a Nondestructive Impulse Device and Damage Model for Unreinforced Concrete

Unconstrained compression waves were measured using a newly developed, nondestructive, short impulse excitation device developed for long-term structural health monitoring. The measurements, using this innovative device, were used to determine the variation in the first longitudinal modal frequency as a function of loading magnitude and loading cycles to failure of various concrete mixes. Longitudinal frequency and cumulative energy variations were found to be a function of concrete compressive strength. These results imply that higher-strength concrete more easily absorbs energy and restricts the growth of microcracks. Based on the results, a new damage model is proposed that was shown to correlate with measured values to within 7%. This proposed model was found to have a closer correlation than Miner’s hypothesis and damage index models from other reviewed research.