Maintenance of reusable mine workings during the augering mining of coal seams

The augering mining of thin and very thin coal seams has been proposed for using the efficiency of this task, related to the stability of reusable mine workings. The interrelation has been established and optimized between the support loading parameters in the extraction working during the augering mining of thin and very thin coal seams with the stress-strain characteristics of the protective monolithic strip of variable rigidity. The strength properties of sand-cement stone for the erection of rigid and yieldable parts of the protective strip are studied. The regression equations are obtained, which allow to determine the rational force, deformation and geometric parameters of the “support – protective strip” system elements during the extraction workings maintenance.

Numerical study into the effects of effective angle of attack motions on energy extraction performance of parallel foils

The effects of different effective angle of attack motions on flapping foil are considered. Energy extraction characteristics of parallel foils with combined plunging and pitching motions at multiple working conditions are systematically analyzed. The energy extraction processes of dual foil at different effective angle of attack motions and reduced frequencies are simulated, respectively. In the range of parameters discussed in this paper, the increase of Ke improves the energy extraction performance of foil effectively. Every effective angle of attack motion has a frequency which can obtain the optimal extraction performance. The optimal energy extraction working condition is Ke = 2 and k = 0.8, where the extraction efficiency of dual foil achieves 25.8%. The synchronicity of the aerodynamic lift and the plunging motion is increased with increase in Ke. This paper provides a significant reference to the further study and popularization in engineering practice of parallel foils energy extraction.

Investigation of the influence of flushing the working gap on the effects of electrodischarge machining (EDM)

This paper discusses experimental results of research on the assessment of the impact of working gap flushing effects processing. The study was conducted for drill trepanation at two variants feed fluid in the treatment zone (injection and extraction working fluid). The influence of productivity, surface topography.

Calculation Model of Airflow Temperature and Simulation System in Coal Mine

With the rapid development of coal mine resources, heat harm in deep mine is one of the key problems to be solved in our country. In this article, through analyzing the different heat sources of the mine,we get the calculation model of airflow temperature which is related to the different feature points of shaft , horizontal and slant roadways and extraction working areas.We also take the actual geological conditions into consideration and build simulation system in coal mine to imitate and budget the airflow temperature and air amount in roadway which is at different ventilation system conditions. And it can provide theoretical and technical basis for the optimization scheme research of mine ventilation system , the ways to choose the mine refrigeration system and installation position of air cooler.

An in vivo Evaluation of Different Methods of Working Length Determination

ABSTRACT Objective The purpose of this in vivo study was to compare the ability of digital tactile, digital radiographic and electronic methods to determine reliability in locating the apical constriction. Materials and methods Informed consent was obtained from patients scheduled for orthodontic extraction. The teeth were anesthetized, isolated and accessed. The canals were negotiated, pulp chamber and canals were irrigated and pulp was extirpated. The working length was then evaluated for each canal by digital tactile sensation, an electronic apex locator (The Root ZX) and digital radiography. The readings were then compared with post-extraction working length measurements. Results The percentage accuracy indicated that EAL method (Root ZX) shows maximum accuracy, i.e. 99.85% and digital tactile and digital radiographic method (DDR) showed 98.20 and 97.90% accuracy respectively. Clinical significance Hence, it can be concluded that the EAL method (Root ZX) produced most reliable results for determining the accurate working length. How to cite this article Mandlik J, Shah N, Pawar K, Gupta P, Singh S, Shaik SA. An in vivo Evaluation of Different Methods of Working Length Determination. J Contemp Dent Pract 2013;14(4):644-648.

The Study of the Methane Oxidation in Soil Cover under Extraction Condition

The methane transport was effected by the oxygen reaction across the cover soil. The air flow into the cover could be contribute to methane oxidation, when the extraction working. The gas flow and transport were the coupling process, which must be considered to evaluate the methane reaction in landfill cover. Both of the maximum oxidation rate and permeability of the soil was the critical index for assessing the methane outflow the cover from the landfill. It will provide technological support and theoretical evidence for the evaluation of the methane removal under the gas extraction system in landfill cover.