Analysis and evaluation of fragment size distributions in rock blasting at the Erdenet Mine

Master's Project (M.S.) University of Alaska Fairbanks, 2015Rock blasting is one of the most important operations in mining. It significantly affects the subsequent comminution processes and, therefore, is critical to successful mining productions. In this study, for the evaluation of the blasting performance at the Erdenet Mine, we analyzed rock fragment size distributions with the digital image processing method. The uniformities of rock fragments and the mean fragment sizes were determined and applied in the Kuz-Ram model. Statistical prediction models were also developed based on the field measured parameters. The results were compared with the Kuz-Ram model predictions and the digital image processing measurements. A total of twenty-eight images from eleven blasting patterns were processed, and rock size distributions were determined by Split-Desktop program in this study. Based on the rock mass and explosive properties and the blasting parameters, the rock fragment size distributions were also determined with the Kuz-Ram model and compared with the measurements by digital image processing. Furthermore, in order to improve the prediction of rock fragment size distributions at the mine, regression analyses were conducted and statistical models w ere developed for the estimation of the uniformity and characteristic size. The results indicated that there were discrepancies between the digital image measurements and those estimated by the Kuz-Ram model. The uniformity indices of image processing measurements varied from 0.76 to 1.90, while those estimate by the Kuz-Ram model were from 1.07 to 1.13. The mean fragment size of the Kuz-Ram model prediction was 97.59% greater than the mean fragment size of the image processing. The multivariate nonlinear regression analyses conducted in this study indicated that rock uniaxial compressive strength and elastic modulus, explosive energy input in the blasting, bench height to burden ratio and blast area per hole were significant predictor variables in determining the fragment characteristic size and the uniformity index. The regression models developed based on the above predictor variables showed much closer agreement with the measurements

Discovery of a red quasar with recurrent activity

We report a new double-double radio quasar, DDRQ, J0746$+$4526 which exhibits two cycles of episodic activity. From radio continuum observations at 607 MHz using the GMRT and 1400 MHz from the FIRST survey we confirm its episodic nature. We examine the SDSS optical spectrum and estimate the black hole mass to be (8.2$\pm$0.3)$\times$10$^7$M$_\odot$ from its observed MgII emission line, and the Eddington ratio to be 0.03. The black hole mass is significantly smaller than for the other reported DDRQ, J0935+0204, while the Eddington ratios are comparable. The SDSS spectrum is significantly red continuum dominated suggesting that it is highly obscured with ${E(B-V)}_{host}=0.70\pm0.16$ mag. This high obscuration further indicates the existence of a large quantity of dust and gas along the line of sight, which may have a key role in triggering the recurrent jet activity in such objects.Comment: 5 pages, 3 figures, 1 table. Accepted for publication in Ap

Path Interdependence in a Dynamic Two Country Heckscher-Ohlin Model

The closed economy neoclassical model predicts lung-run convergence in per-capita income. We show, within a neoclassical framework, that international trade among two countries differing only in their initial capital endowment generates long-run income differences. Our results suggests that trade creates opposite incentives to accumulate capital. Transitionally, the returns to investment with trade are smaller for countries initially less endowed with capital as when compared to their autarchic situation, while the reverse happens for those countries most endowed with capital. Thus, countries starting with relatively less (more) capital end, in the long run, with less (more) capital than in autarchy.International trade; Development; Multiple Equilibria

Path Interdependence Among Early and Late Bloomers in a Dynamic Heckscher-Ohlin Model

The closed economy neoclassical growth model predicts convergence to a capital stock level that is independent of its initial level, suggesting that discrepancies in per capita income among the world’s economies should largely disappear in the long-run. This paper shows that international trade among countries differing only in their level of initial capital is sufficient to generate long-run income differences across countries. The long-run level of capital of the country most initially endowed with capital is shown to exceed the level of capital otherwise obtained in autarchy while the country least endowed converges to a capital stock lower than would otherwise be obtained in autarchy.International trade, Development, Multiple Equilibria, International Relations/Trade, O41, F43, F11,

Optical and radio properties of extragalactic radio sources with recurrent jet activity

We present a sample of 74 radio sources with recurrent jet activity. The sample consists of 67 galaxies, 2 quasars and 5 unidentified sources, selected from the published data or are newly recognized. The sample's redshift range is 0.002 < z < 0.7 and the size of inner and outer structures varies from 0.02 to 4248 kpc. We analyse the optical and radio properties of the sample and compare them with the characteristics of ordinary one-off FRII radio sources. With the help of stellar population modelling, we derive black hole masses and stellar masses of host galaxies of 35 restarting radio sources, finding that the black hole masses in restarting radio sources are comparable to those of typical single-cycle FRII radio sources. The obtained median values of log M$_{BH}$ are 8.58 and 8.62 M$_{\odot}$ Unlike the black hole masses, the stellar masses in restarting radio sources tend to be smaller than in the FRII sources. Although the stellar populations of the hosts of recurrent activity sources are dominated by old stars, a significant fraction of young stars can be observed as well. Based on the Sloan Digital Sky Survey photometric observations, we also analyse the morphology of the host galaxies and obtained significantly smaller concentration indices for the restarting radio sources when compared to the classical FRII hosts. This effect can be interpreted as a result of frequent merger events in the history of host galaxies of restarting radio sources.Comment: 21 pages, 17 figure