Underground mining method selection by decision making tools

Underground mining method selection is one of the most important decisions that mining engineers have to make. Choosing a suitable underground mining method to extract a mineral deposit is very important in terms of economics, safety and productivity of mining operations. In real life, underground mining method selection is one of the multiple attribute decision making (MADM) problems and decision makers have always some difficulties in making the right decision in the multiple criteria environment. Analytic hierarchy process (AHP) and Yager’s methods are the MADM tools and can be used for selection of the best underground mining method by considering the problem criteria. In this study, a computer program (UMMS) based on the AHP and the Yager’s method was developed to analyze the underground mining method selection problems and produce the best underground mining method swiftly for different deposit shapes and ore bodies.     

General Irrigation Planning Performance of Water User Associations in the Gediz Basin in Turkey

In this study, an evaluation has been made of the realization level of the planned targets in irrigation planning for all of the 13 water user associations (WUAs) of the Gediz Basin. This evaluation was made according to six performance indicators: level of realization of irrigation ratios, level of realization of crop pattern, dependability, adequacy, efficiency, and equity for the years 1999–2002. Seven associations were successful in irrigation ratio realization, and four were successful in crop pattern. Failure of other WUAs can be reduced by collecting farmers’ declarations and evaluating them with greater care and sensitivity. Water delivery in the general irrigation plan was found to be poor with regard to dependability and equity, and good with regard to the indicators of adequacy (except in the year 2001) and efficiency. In order to improve dependability, the period when water is diverted from the source and the period when water is needed must coincide completely. In order to improve equity, delivery of water to WUAs must be carried out taking account of water requirements predicted in the general irrigation plan. When these two indicators are improved, adequacy and efficiency will improve also.     

Time-optimized hole sequence planning for 5-axis on-the-fly laser drilling

On-the-fly laser drilling requires the use of acceleration continuous trajectories, which are typically planned using time parameterized spline functions. In this operation, the choice of hole drilling sequence, and positioning timings in between the holes, play a critical role in determining the achievable cycle time. This paper presents a new algorithm for sequencing 5-axis on-the-fly laser drilling hole locations and timings. The algorithm considers machine tool and process constraints, as well as the temporal nature of the final commanded spline trajectory. The achievable productivity and motion smoothness improvement are demonstrated in the production of a gas turbine combustion chamber panel.     

Synthesis and reaction mechanism of Ti3SiC2 ternary compound by carbothermal reduction of TiO2 and SiO2 powder mixtures

The present study aims to investigate synthesis of Ti₃SiC₂ from TiO₂ and SiO₂ powder mixtures by carbothermal reduction method. Equilibrium TiO₂–SiO₂–C ternary phase diagram was used to predict the conditions for the formation of Ti₃SiC₂ at 1800 K under Ar atmosphere. A reactant mixture with a TiO₂:SiO₂ molar ratio of 1.5 and a C content of 68.75 mol% (26.86 wt%) was initially selected among the thermodynamically favorable reactant compositions for the experimental studies. Two different C sources, graphite flakes and pyrolytic C coating, were used to synthesize Ti₃SiC₂ at 1800 K under Ar atmosphere. When graphite flakes were used, the products contained a trace amount of Ti₃SiC₂ phase along with major TiC and minor SiC phases. Whereas, pyrolytic C coating on the oxide particles resulted in the products with much higher Ti₃SiC₂ contents owing to the close contact between the reactants. Optimal C concentration for the C coated oxide mixtures with a TiO₂:SiO₂ molar ratio of 1.5 was determined to be 30.05 wt% under the experimental conditions studied. Ti₃SiC₂ content of the products obtained from this reactant was observed to increase with reaction time to 31 wt% at 75 min beyond which it gradually decreased. XRD studies indicated that the product with the highest ternary carbide content also contained TiC and a trace amount of SiC. SEM-EDS analyses showed that this sample essentially consisted of spherical fine TiC particles and Ti₃SiC₂ nanolaminates. Equilibrium thermodynamic analysis of the TiO₂–SiO₂–C system suggested that the reaction of solid Ti₂O₃ with SiO and CO gases may play a dominant role in the formation of Ti₃SiC₂.     

The effect of electric and magnetic fields on the operation of a photovoltaic cell

In this work, we have investigated the effects of electric and magnetic fields on the operation of a CdS/CuInSe₂ photovoltaic cell. Various electric field intensities changing from 0 to 35000 V_dc/m, were applied to the sample while it was irradiated by a He–Ne laser with a wavelength λ=670 nm. As a result, the typical values for the open circuit voltage of the photovoltaic cell significantly changed with various intensities of the electric field E_dc. We also applied magnetic fields varying from 0.003 to 0.079 T using a solenoid with an inductance of 10.55 mH and the response of the sample was observed. In the third step of the experiment, instead of the laser beam, various intensities of white light of 50, 100,150 and also 250 lux were utilised. 250 lux was measured to be equivalent to the radiation power of He–Ne laser beam on the surface of the photovoltaic cell. The effect of electric fields from 0 up to 3×10⁵ V_dc was applied and some significant experimental results were obtained. As a result of the illumination of the photovoltaic cell by the stimulated and spontaneous light emission sources under the effect of various intensities of electric field E_dc, different electrical behaviours were observed.     

Dynamics of four-wheel-steering vehicles

In this paper we present an optimised 3 degrees-of-freedom non-linear dynamic model of a four-wheel-steering (4WS) vehicle. As variables, we retain the lateral velocity V, the rolling velocity p and yaw velocity r. The front steer angle δ_f and rear steer angle δ_r are considered to be linear functions of the steering wheel angle θ_s and of dθ_s/dt, the proportionality parameters being k _1f, k _2f for δ_f and k _1r, k _2r for δ_r. The parameters k _1f, k _2f, k _1r, k _2r are optimised by use of the BOX mathematical algorithm. In a first optimisation loop we minimise the sideslip angle β of the vehicle and in a second optimisation loop we assure, that the resultant (taken in the centre of gravity of the vehicle) of all the transversal forces F _y applied on the wheels of the vehicle (reaction forces contained in the road plane), give a component F _yx along the longitudinal axis of the vehicle, that takes a non negative value. This assures, that the motor of the vehicle will not waste fuel to overcome resistance forces originating from the steering system of the vehicle. A numerical application is also presented for a 4WS vehicle negotiating a curve at constant velocity. The results are compared to those obtained by two models frequently used in the literature. The comparison testifies on the superiority of our model for the application presented here.