Papers by Keyword: Fragmentation

Abstract: This study highlights the performance analysis of rock fragmentation on mine excavation process efficiency and powder factor, instantaneous dig factor and loading efficiency. The power regression analysis of the relationship between powder factor and loading efficiency, defines the highest loading efficiency at the optimal powder factor ranging from 0.48 to 0.52 kg/m³. Loading efficiency with powder factor 0.50 kg/m³ is 0.469 while loading efficiency with powder factor 0.30 kg/m³ is 0.253. However, when considering the powder factor of more than 0.80 kg/m³, the efficiency dropped to 0.217 due to the generation of excessive fines and the reduction of the bucket fill rates. The R² value of the regression model is 0.995, thus, confirming the high predictive ability of powder factor while measuring the loading efficiency. In comparison to the original parameters, the optimized powder factor selection reduced the cycle times by as much as 22.4% and increased fragmentation consistency, according to the study. This study potentially highlights the need for enhanced blast design, which optimises total excavation costs and maximises mine productivity.

Abstract: This research was carried out to compare the performance of ANFO and Ammonium Nitrate on fragment size distribution by using the ANFO and AN as the column charge in blasting operations, measuring the fragmentation size after each blasting operation, characterizing the fumes evolving from the blasting operation in each case and compare the performance of the ANFO and AN. The densities of the rock deposit were derived as 2.638 g/m³ and 2.622 g/m³ for Block A and Block B respectively. The rebound hardness tests ranged from 47 to 61 for Block A and Block B from 48 to 54. The total explosive charge used for each of the blocks was 0.1 kg. The muckpile magnification ratio for Block A was 0.008 and Block B was 0.004. The fragmentation sizes for Block A range from 1.869 cm to 19.411 cm and Block B from 2.414 cm to 37.177 cm. The magnification ratio and fragment sizes show that Block A has better fragmentation than Block B. Ammonia gas was not present in the area of study before blasting but the fume emitted after first blasting with ANFO produced 0.08% of Ammonia gas and after the second blasting with AN 0.07% were produced. The oxygen level was reduced from 20.9% before blasting to 19.2% after the first blasting and 19.1% after the second blasting. It was deduced that blasting with ANFO generated more Ammonia gas than blasting with AN but the Oxygen level when ANFO is used was higher than when AN is used. Keywords: Blasting, density, explosive, fragmentation, magnification ratio

Abstract: An alternative to thermal pyrolysis is catalytic pyrolysis, which provides a higher conversion of raw materials at a lower temperature than thermal pyrolysis, that is, it reduces the energy intensity of the process and increases the selectivity of pyrolysis for lower alkenes.

Abstract: Following the growing interest in monitoring the status, behavior and impact of micropollutants in the environment, a significant area of concern revolves around the degradation of plastics, which is closely associated with a range of environmental risks. The long-term goal is to investigate the degradation process of plastics in an aqueous environment within controlled laboratory settings and analyze the status of degraded particles over a specific period. The proposed methodology, which is the subject of this paper, aims to achieve this objective. Over the period of one year, both conventional and biodegradable plastics are subjected to the combined effects of UV radiation and water motion. This paper presents the design of laboratory setting and experimental setup for conducting the degradation process. Based on its implementation, the degradation process is evaluated including weight loss and conducting microscopic and FTIR analysis of microplastic particles (MP). By gaining a better comprehension of these processes, we expect to be able to effectively mitigate the adverse environmental consequences caused by plastics.

Abstract: Model research tests of plastic deformation, fragmentation and flow of aluminum alloy material of Al-Mg-Sc-Zr system under high loaded friction in pair with a steel counterbody of a complex shape and comparison of the obtained result with the structure formed by friction stir welding have been carried out. The conducted studies show that the structure formed by extrusion of the material from the friction zone and its compaction in the channel of the counterbody is, in general, close in structure to the structure formed by friction stir welding of similar material. The distinguishing features of the structure formed in the model experiments on friction include the introduction into the stirring zone of material with deformed large-crystal structure, increased grain size of the stirring zone, the presence of defects and differences in the geometry of the stirring zone.

Abstract: We show a correlation between nanoscale damage and fragmentation length scale through atomistic simulations. We simulated homogeneously expanding perfect, single crystal copper at rates ranging from 1E+08 to 3E+10 s^-1 and temperatures from 200 to 1000 K. Damage was quantified in terms of void number density, average void volume, and void volume fraction. We quantified fragmentation size in terms of a length scale parameter, the solid volume per void surface area. A-1⁄2 power law relationship between the fragment length scale and strain rate was observed following the predictions of Mott. The fragmentation length scale and the maximum void number density are strongly correlated for this damage mechanism. We can scale up the relationships between damage and fragmentation observed in the molecular dynamics simulations to motivate a continuum scale fragmentation model.

Abstract: The effects of Temperature-Strain-Time parameters at the Thermomechanical Processing (TMP) of austenitic, duplex and pearlitic structural steels on the mesostructure formation has been studied based on the laboratory, industrial experiments and TEM analysis. The fragmented dislocation substructure observed in steels with a different carbon, nitrogen, titanium, niobium content as well as recrystallization gave evidence that TMP effects the work-hardening and softening behaviour. The problem of mesostructure appearing in various steels and alloys due to various modes of TMP used hot and hot-warm deformation is discussed. The role of plastic strain in the formation of mesostructure and the relation between the changes in the crystal structure due to TMP and the mechanical properties of the steels are considered.

Abstract: This paper presents the brief review of Chelyabinsk group of meteoroid, bolide and meteorite "Chelyabinsk" investigations. Height of the maximum of the main flash of Chelyabinsk bolide is 30 km. Only 1% of meteoroid mass arrived to the Earth surface in the form of meteorites while the most part of meteoroid became dust. During four days the dust had circumnavigated the globe and formed stratospheric dust belt. This new dust belt, located above the Junge aerosol layer, has persisted over at least a three-month period. The mass distribution of found meteorites is lognormal. This shape argues that fragmentation process of initial body happened randomly and in a cascade way. Transparent or translucent mineral filaments firmly linked to the particles were found in the meteoritic dust. In metallic phases of the meteorite mainly Fe-rich compounds exist. Very interesting topics of next research are magnetic properties of Fe-Ni phase, because of cosmic synthesis conditions. Meteoroids like "Chelyabinsk" fall on average once every 30 years. Therefore the problem of "asteroid and comet danger" should be expanded to the problem of "meteoroid, asteroid and comet danger".

Abstract: Passive Solid State Nuclear Track Detectors (SSNTDs) have been employed successfully during the past two decades in space radiation studies due to their excellent physico-chemical properties. They are useful for charged particle detection in the linear energy transfer (LET) range above the threshold value of ~10 keV μm^-1. It was applicable for measurement of cosmic ray primary and secondary particles, including recoil nuclei, projectile and target fragments and secondary neutrons in past projects such as DOSMAP, BRADOS, ALTCRISS, Matroshka or recently in progress as SPD, DOSIS, as well as, in ground based experiment as Icchiban. The continuous development in the understanding of the track formation mechanism and improvement of detection techniques have resulted in the determination of the cosmic ray LET spectrum with less uncertainties and provided improved assessment of the dose burden of astronauts and helped to increase the effectiveness of radiation shielding of spaceships. Space dosimetry by nuclear track methodology stresses the advantages of passive systems for cosmic radiation field studies due to their robustness, compact dimensions, and complete independence from external power supply. SSNTDs cope also with requirement imposed by portable area monitoring or personal dose integrator to assess radiation risk of astronauts during intra or extra-vehicular activity. This review tries to provide a short summary about fundamentals and applications of space radiation studies using SSNTDs.Contents of Paper

Abstract: Columnar jointed basalt rock block is small, but has a longitudinal wave velocity, high modulus characteristics. This article is based on the structure of surface measurements, acoustic testing, and field distortion tests results, from the liquid structure, structural plane development situation, etc., analyses the causes of this phenomenon.