VH-nuclei cosmic-ray tracks in chondrites as indicators for radiation-thermal history of the meteorite matter at the early stage of solar system primary body formation

VH-nuclei cosmic-ray track study in silicate mineral grains extracted from matrix and chondrules of no enriched by solar gas chondrites has been performed. A broad range of track densities, typical track density grouping and absence of track density gradients have been observed in these grains. The traces of low energy cosmic-ray VH-nuclei particles that were stored at the early pre-accretion history of the meteorite parent body formation have been established.     

TEM investigations of heavy ion latent tracks

High resolution observations of GeS single crystals with a 400 keV transmission electron microscope (TEM) were carried out. The GeS was irradiated at the UNICAC with heavy ions at several MeV/u specific energy. The imaging of the tracks revealed relatively large amorphous cores of elliptical cross section, oriented with respect to the crystal lattice.     

Study of fossil tracks due to VH and VVH groups of cosmic ray nuclei in olivine crystals from Luna-16 and Luna-24

The olivine crystals from lunar regolith samples taken by the Soviet unmanned spacecrafts Luna-16 and Luna-24 were investigated. Eleven 0.5 –1.0 mm size olivine crystals were mounted in epoxy, polished and then etched in modified WO₄ solution. The Fe-group track densities up to 10⁸ tracks.cm⁻² (Fe-group) were measured under optical microscope. The tracks of length greater than 30 microns due to Z ≥ 36 cosmic ray nuclei are counted for VVH tracks density for all the crystals. The VVH / VH track densities ratio for these lunar olivine crystals varies from 1.25×10⁻⁴ to 2×10⁻³. It corresponds to the averaged depth of these crystals in lunar soil of 2–8 cm during galactic cosmic ray exposure. Lunar crystals are well suited for VVH track studies due to a very high track density. Two crystals were annealed at 430°C for 32 hrs. This procedure eliminates iron group tracks completely and leaves etchable tracks of nuclei with Z 50 even in the olivine crystals with Fe-group tracks up to 1–2×10⁸ tracks cm⁻². We were able to measure two tracks with the length 195 and 210μm which were produced by Th---U group of Galactic cosmic ray nuclei.     

A novel method for detecting and counting overlapping tracks in SSNTD by image processing techniques

Overlapping object detection and counting is a challenge in image processing. A new method for detecting and counting overlapping circles is presented in this paper. This method is based on pattern recognition and feature extraction using “neighborhood values“ in an object image by implementation of image processing techniques. The junction points are detected by assignment of a value for each pixel in an image. As is shown, the neighborhood values for junction points are larger than the values for other points. This distinction of neighborhood values is the main feature which can be utilized to identify the junction points and to count the overlapping tracks. This method can be used for recognizing and counting charged particle tracks, blood cells and also cancer cells. The method is called “Track Counting based on Neighborhood Values” and is symbolized by “TCNV”.     

Wayside acoustic defective bearing detection based on improved Dopplerlet transform and Doppler transient matching

The diagnosis of train bearing defects plays a significant role in maintaining the safety of railway transport. However, the phenomenon of Doppler Effect in the acoustic signal recorded by the wayside Acoustic Defective Bearing Detector (ADBD) system leads to the difficulty for fault diagnosis of train bearings with a high moving speed. This paper proposes a double-searching solution based on improved Dopplerlet transform and Doppler transient matching to overcome the difficulty in wayside acoustic bearing diagnosis. In the solution, the first searching procedure is to extract necessary parameters of Doppler Effect under the situation with very low signal-to-noise ratio (SNR) based on an improved Dopplerlet transform. Using the obtained parameters, the Doppler Effect can be embedded into the constructed periodic Laplace wavelet transient models. Subsequently, the second searching procedure is conducted to search fault impact period of the defective bearing through an operation, called Doppler transient matching, which is to calculate the correlation coefficient between the Doppler transient model and the filtered raw signal with the Doppler Effect. The proposed double-searching algorithm can adapt to the real Doppler Effect situation and extract the exact fault impact period from the Doppler distorted signal, and thus shows powerful capability to analyze wayside acoustic signals from train bearings. The proposed wayside acoustic diagnostic scheme is verified by means of a simulated Doppler distorted signal with a very low SNR (−20 dB) and the experiments conducted on train bearings. The results indicate that the proposed algorithm is effective and has obvious advantages for ADBD system.     

Correlation between rolling noise generation and rail roughness of tangent tracks and curves in time and frequency domains

Despite considerable advantages of the railway track over other means of transportation, noise pollution is the main adverse consequence of railway transportation. The basic cause of railway noise is rail corrugation. Although characteristics of railway noise have been considerably studied in the literature, rail corrugation effects on rolling noise generation in tangent tracks and the curves have not been sufficiently investigated. This research addresses the limitations of the current understanding of the rolling noise generation by investigating rail corrugation effects on rolling noise in tangent tracks and curves. This research was made based on the results obtained form a thorough field investigation carried out in a railway line which includes tangents tracks and sharp curves. A track geometry recording car was used to measure rail corrugations. For this purpose, an indirect method was developed in this research to obtain rail corrugation patterns from the data recorded by the track recording car. The effectiveness of the new method was shown. The induced noises were recorded using two particular types of microphones and implementing the method suggested by the ISO 3095 Standard. The rolling noise signal was distinguished from the total noise, using Butterworth Band-Pass Filtering. The role of rail corrugations in the rolling noise was discussed. Correlations were made between various types of corrugations and the induced noises. The results were presented and discussed in the spatial and frequency scales. Results obtained have led to new findings in rail corrugation effects on rolling noise generation. This research paves a way toward a better understanding of rolling noise sources and the parameters influencing the noise.     

Gd, U, Pu and Cm alpha particle energy analysis using tracks in solids

This paper presents advances in a procedure for alpha particle analysis using the nuclear tracks formed in solid-state materials. This method is based on the relationship between the energy deposited in the material by ionizing particles and the track developed after a well-established chemical process. The experimental study included alpha particles in the energy range from 3.2 to 5.8 MeV emitted by ¹⁴⁸Gd, ²³⁸U, ²³⁹Pu and ²⁴⁴Cm. The quantitative results provide a clear signature to identify each one of the radioisotopes based on the formed track parameters. The track analysis is performed with a digital image analysis system associated with a PC mathematical processor. The wide range energy response makes this method a promising analysis system.     

A necessary condition for the appearance of damage-induced surface-topography during particle bombardment

A first approach to the establishment of an “order-of-magnitude” criterion for the initiation of damage-induced surface topography on clean and well-polished metal single crystals is proposed. It is based on a model proposing a mechanism of preferential erosion of parts from the sample surface due to a local increase of sputtering yield above “extensive defects”. These “extensive defects”, resulting of the migration of the point-defects, created during the collision-cascade started by the incoming ions, can indeed influence the sputtering yield if they are located close under the surface, i.e. when the surface has regressed, due to sputtering, to the level where these “extensive defects” have been formed.

The condition implies that the formation of “extensive defects” must have taken place before the surface reaches them. The condition is written in terms of the irradiation parameters and quantities characteristic for the migration of point-defects due to the presence of a potential gradient related to the “extensive defects” under formation.     

Critical approach distances and critical angles for channelling

The critical angles and critical approach distances, which determine the limits for the channelling of energetic ions, down open crystal directions are established by the methods of computer simulation and compared with simple analytical models. For non-vibrating rows or planes a good agreement between the two is obtained. The complicating effects of thermal vibrations can be accounted for by empirical formulae.