Numerické řešení procesu rozpojování tvrdých hornin. Část 2

This paper focuses on a numerical analysis of a hard rock (ore) disintegration process. A bit moves into the ore and subsequently disintegrates it. The disintegration (i.e. fracture of ore) is solved via a deterministic approach (FEM) and a probabilistic approach (FEM in combination with the SBRA - Simulation-Based Reliability Assessment method, i.e. Monte Carlo simulations, stochastic inputs). The ore is disintegrated by deactivating the finite elements satisfying fracture conditions. The results are compared with experiments. The application of the SBRA method is a new and innovative trend in this area. Finally, the probabilistic reliability assessment is mentioned.Článek se zaměřuje na numerickou analýzu procesu rozpojování tvrdých hornin (rud). Nůž se pohybuje do horniny a následně ji rozpojuje. Rozpojování (tj. lom rudy) je řešeno deterministickým přístupem (MKP) a pravděpodobnostním přístupem (MKP v kombinaci s metodou SBRA - Simulation-Based Reliability Assessment, tj. simulace Monte Carlo, stochastické vstupy). Ruda je rozpojována pomocí deaktivace konečných prvků, které splňují podmínky odlomení. Výsledky jsou porovnány s experimenty. Aplikace metody SBRA v této oblasti je novým a inovativním trendem. V závěru je uveden pravděpodobnostní posudek spolehlivosti

Probabilistic Analysis of the Hard Rock Disintegration Process

This paper focuses on a numerical analysis of the hard rock (ore) disintegration process. The bit moves and sinks into the hard rock (mechanical contact with friction between the ore and the cutting bit) and subsequently disintegrates it. The disintegration (i.e. the stress-strain relationship, contact forces, reaction forces and fracture of the ore) is solved via the FEM (MSC.Marc/Mentat software) and SBRA (Simulation-Based Reliability Assessment) method (Monte Carlo simulations, Anthill and Mathcad software). The ore is disintegrated by deactivating the finite elements which satisfy the fracture condition. The material of the ore (i.e. yield stress, fracture limit, Young’s modulus and Poisson’s ratio), is given by bounded histograms (i.e. stochastic inputs which better describe reality). The results (reaction forces in the cutting bit) are also of stochastic quantity and they are compared with experimental measurements. Application of the SBRA method in this area is a modern and innovative trend in mechanics. However, it takes a long time to solve this problem (due to material and structural nonlinearities, the large number of elements, many iteration steps and many Monte Carlo simulations). Parallel computers were therefore used to handle the large computational needs of this problem.

Dynamické charakteristiky nového stroje pro testování únavy železničních náprav - část 2

There were done some proposal calculations for a new testing machine. This new testing machine is determined for a dynamic fatigue testing of railway axles. The railway axles are subjected to bending and rotation (centrifugal effects). For the right proposition of a new machine is very important to know the basic dynamic characteristics of whole system. These dynamic characteristics are solved via FEM (MSC.Marc/Mentat software) in combination with SBRA (Simulation-Based Reliability Assessment) Method (probabilistic Monte Carlo approach, Anthill and Python software). The proposed dimensions and springs of a new machine for fatigue testing of railway axles were used for manufacturing. Application of the SBRA method connected with FEM in these areas is a new and innovative trend in mechanics. This paper is continuation of former work (i.e. easier deterministic approach) already presented in this journal in 2007.Byly provedeny návrhové výpočty nového zkušebního stroje. Tento nový zkušební stroj je určen pro dynamické únavové testy železničních náprav. Železniční nápravy jsou namáhány ohybem a rotací (odstředivé efekty). Pro správný návrh nového stroje je velmi důležité znát základní dynamické charakteristiky celého systému. Tyto dynamické charakteristiky jsou řešeny MKP (MSC.Marc/Mentat software) v kombinaci s metodou SBRA (Simulation-Based Reliability Assessment - pravděpodobnostní přístup Monte Carlo, Anthill a Python software). Navržené rozměry a pružiny nového stroje pro únavové testování železničních náprav byly použity pro výrobu. Aplikace metody SBRA spojené s MKP v této úloze, je novým a inovativním trendem v mechanice. Tento článek je následujícím pokračováním dřívější práce (tj. jednoduchý deterministický přístup) již prezentované v tomto časopise v r. 2007

Sensitivity of VOF simulations of the liquid jet breakup to physical and numerical parameters

AbstractIn this paper the characteristics of the primary breakup of a liquid jet is analyzed numerically. We applied the Volumes of Fluids (VOF) approach utilizing the Direction Averaged Curvature (DAC) model, to estimate the interface curvature, and the Direction Averaged Normal (DAN) model, to propagate the interface. While being used for the first time to predict liquid atomization, this methodology showed a high accuracy. The influence of varying the fluid properties, namely liquid-gas density and viscosity ratio, and injection conditions is discussed related to the required grid resolution. Resulting droplet sizes are compared to distributions obtained through the One-Dimensional Turbulence (ODT) model

Interim guidelines for hospital response to mass casualties from a radiological incident

On September 11, 2001, U.S. symbols of economic growth and military prowess were attacked and thousands of innocent lives were lost. These tragic events exposed our nation\ue2\u20ac\u2122s vulnerability to attack and heightened our awareness of potential threats. Further examination of the capabilities of foreign nations indicate that terrorist groups worldwide have access to information on the development of radiological weapons and the potential to acquire the raw materials necessary to build such weapons. The looming threat of attack has highlighted the vital role that public health agencies play in our nation\ue2\u20ac\u2122s response to terrorist incidents. Such agencies are responsible for detecting what agent was used (chemical, biological, radiological), event surveillance, distribution of necessary medical supplies, assistance with emergency medical response, and treatment guidance.In the event of a terrorist attack involving nuclear or radiological agents, it is one of CDC\ue2\u20ac\u2122s missions to insure that our nation is well prepared to respond. In an effort to fulfill this goal, CDC, in collaboration with representatives of local and state health and radiation protection departments and many medical and radiological professional organizations, has identified practical strategies that hospitals can refer to in preparing for and responding to a radiological terrorism event involving mass casualties.The guidance focuses on six key areas: (1) notification and communication, which emphasizes the importance of hospitals working with their communities and public health agencies on developing emergency communication plans; (2) triage; (3) patient management, including decontamination, treatment, care of special populations, discharge and follow up, and patient mental health concerns; (4) healthcare provider protection, including staff training and practitioner mental health concerns; (5) surveillance, and (6) community planning

Comminution in the Minerals Industry

Size reduction processes represent a significant part of the capital as well as the operating cost in ore processing. Advancing the understanding of and improving such processes is worthwhile since any measurable enhancement may lead to benefits, which may materialize as reductions in energy consumption or wear or improved performance in downstream processes. This book contains contributions dealing with various aspects of comminution, including those intended to improve our current level of understanding and quantification of particle breakage and ore characterization techniques that are relevant to size reduction, as well as studies involving modeling and simulation techniques. The affiliations of the authors of the articles published in this book span 14 countries around the globe, which attests to the highly international nature of research in this field. The themes of the manuscripts also vary widely, from several that are more focused on experimental studies to those that deal, in greater detail, with the development and application of modeling and simulation techniques in comminution. Size reduction technologies more directly addressed in the manuscripts include jaw crushing, vertical shaft impact crushing, SAG milling, stirred milling, planetary milling, and vertical roller milling. Ores involved directly in the investigations include those of copper, lead–zinc, gold, and iron as well as coal, talc, and quartz