Pillars are designed to ensure regional stability or local support in stopes and along drifts, or to yield under a measure of control. In all cases, the strength of the material and the variations in strength must be known both for the pillar and for the roof and floor. The stability in longwall faces depends mainly on the interaction between the roof strata, face support, roadway support and dimensions of pillars. The main aim of this paper is to apply rock mass classification systems to longwall pillar design at Abu-Tartur mining area. The pillar load is estimated taking into account the physical and mechanical properties of phosphate deposit and roof rock, panel width, mining height, depth below surface. Two methods from classification systems are used in calculation pillars stress and strength to pillars design namely Geological Strength Index (GSI) and Rock Mass Rating (RMR) systems. GSI values for immediate, main roof rocks and phosphate ores are determined from geological conditions, as lithology, structure of the interlocking of rock blocks and the conditions of the surfaces between these blocks. RMR value can be determined by correlation it with GSI system. The pillar widths calculated by applying rock mass classifications (GSI& RMR) are 49m and 64m at a factor of safety 2 and panel width 100m with extraction ratios of 70 and 64 % respectively. The data used in calculations are collected from geological reports of the company and from laboratory tests of phosphate ores and shale rocks in the roof.

Electroless Nickel-Phosphorus coatings have had a lot of interest in various industries due to outstanding characteristics. Some of the highlighted characteristics of electroless Ni-P coatings are superior corrosion and wear resistance. But the effectiveness of electroless Ni-P coating in resisting cavitation damage is not studied so well and is not so clear. In the present investigation, electroless Ni-P coatings were prepared at various conditions including the type of bath, heat treatment temperature and plating solutions composition. The properties of electroless Ni-P coatings were characterized using X-ray diffraction technique (XRD), energy dispersive X- ray (EDX) optical microscope, and microhardness tester. The cavitation erosion tests were carried out to study the effect bath type, heat treatment temperature and plating solutions composition on the deposit coatings. The XRD results indicate that the as-deposit had crystalline structure for alkaline bath and amorphous structure for acid bath. Heat treatment of the coatings produced mixture of polycrystalline phases. The thickness of deposit films depend on the bath type and concentration and were the least for alkaline baths. Maximum hardness of heat treated samples was found to depend on the solution composition and occurs at temperature 300 °C and 400°C. The highest erosion resistance of the coatings was observed for the heat treated deposits at temperature of 650 °C, and comes to the fore the coatings formed in alkaline baths followed by that formed in acid baths. The best erosion resistance for deposits formed in alkaline baths is attributed to the small thickness and crystalline structure. The results showed also that the cavitation erosion resistance is independent on surface hardness.

This paper considers the problem of controlling a given linear time invariant (LTI) system described by a rational transfer function using a PI controller. A method based on graphical and computational tools has been proposed. This method specifies a PI controller (Kp and Ki) that satisfies both frequency domain specifications (a specified gain or phase margin) and minimum integral time absolute error (ITAE).

This paper presents the robust optimal shifting of eigen values control design and application for load frequency control. A method for shifting the real parts of the open-loop poles to any desired positions while preserving the imaginary parts is constant. In each step of this approach, it is required to solve a first-order or a second-order linear matrix Lyapunov equation for shifting one real pole or two complex conjugate poles respectively. This presented method yields a solution, which is optimal with respect to a quadratic performance index. Load-frequency control (LFC) of a single and two area power systems is evaluated. The objective is to minimize transient deviation in frequency and tie-line power control and to achieve zero steady-state errors in these quantities. The attractive feature of this method is that it enables solutions to complex problem to be easily found without solving any non-linear algebraic Riccati equation. The control law depends on finding the feedback gain matrix and then the control signal is synthesized by multiplying the state variables of the power system with determined gain matrix. The gain matrix is calculated one time only and it works over wide range of operating conditions. To validate the powerful of the proposed optimal pole shifting control, a linearized model of a single and two interconnected area load frequency control is simulated.

This paper is aimed at calculating corona current-voltage characteristics of a new design of an electrostatic motor with a cylindrical rotor made from aluminium foil and multi stator copper electrodes. The stator electrodes are alternately stressed positively and negatively. The corona currents emitted from positively and negatively-stressed electrodes are calculated being dependent on the applied voltage and motor geometry. The method of calculation is based on simultaneous solution of Poisson’s equation, current density equation and continuity equation for current density. This calls at first for calculation of the spatial distribution of electric field within the motor volume using the accurate charge simulation technique. The calculated current-voltage characteristics of the motor agreed reasonably with those measured experimentally for three motors built-in the laboratory.

This paper is aimed at calculating corona current-voltage characteristics of a new design of an electrostatic motor with a cylindrical rotor made from aluminium foil and multi stator copper electrodes. The stator electrodes are alternately stressed positively and negatively. The corona currents emitted from positively and negatively-stressed electrodes are calculated being dependent on the applied voltage and motor geometry. The method of calculation is based on simultaneous solution of Poisson’s equation, current density equation and continuity equation for current density. This calls at first for calculation of the spatial distribution of electric field within the motor volume using the accurate charge simulation technique. The calculated current-voltage characteristics of the motor agreed reasonably with those measured experimentally for three motors built-in the laboratory.

This paper is aimed at calculating corona current-voltage characteristics of a new design of an electrostatic motor with a cylindrical rotor made from aluminium foil and multi stator copper electrodes. The stator electrodes are alternately stressed positively and negatively. The corona currents emitted from positively and negatively-stressed electrodes are calculated being dependent on the applied voltage and motor geometry. The method of calculation is based on simultaneous solution of Poisson’s equation, current density equation and continuity equation for current density. This calls at first for calculation of the spatial distribution of electric field within the motor volume using the accurate charge simulation technique. The calculated current-voltage characteristics of the motor agreed reasonably with those measured experimentally for three motors built-in the laboratory.

closed bus routes. Transit passengers, in many cases, deal with overlapping bus routes with some routes sharing common sections and stops. Passenger assignment problem is a major task in frequency setting of bus service which aims to minimize passengers and operator costs. In this work, mixed integer mathematical formulation based on passenger choice problem is developed to track each proportion of passengers’ in selecting bus routes for -0- and -1- trips transfer. The proposed model would help for a given transit network and total bus fleet size to minimize network total travel time. It would optimally distribute frequency among bus routes, regarding passengers’ interests in selecting bus routes. It differs from traditional models, since it helps in tracking different users while they are moving on the network. Numerical examples are given to clarify the proposed mathematical formulation. Circular bus routes operational performance is tested using Mandl’s network benchmark problem. Genetic Algorithm has been implemented with Matlab language in solution procedure. Comparing results with previous work indicates that circular bus routes manage in minimizing average user travel time for the same operator cost. The results from this study would help in further work to optimize transit vehicle size and stops distances along each single bus route.

closed bus routes. Transit passengers, in many cases, deal with overlapping bus routes with some routes sharing common sections and stops. Passenger assignment problem is a major task in frequency setting of bus service which aims to minimize passengers and operator costs. In this work, mixed integer mathematical formulation based on passenger choice problem is developed to track each proportion of passengers’ in selecting bus routes for -0- and -1- trips transfer. The proposed model would help for a given transit network and total bus fleet size to minimize network total travel time. It would optimally distribute frequency among bus routes, regarding passengers’ interests in selecting bus routes. It differs from traditional models, since it helps in tracking different users while they are moving on the network. Numerical examples are given to clarify the proposed mathematical formulation. Circular bus routes operational performance is tested using Mandl’s network benchmark problem. Genetic Algorithm has been implemented with Matlab language in solution procedure. Comparing results with previous work indicates that circular bus routes manage in minimizing average user travel time for the same operator cost. The results from this study would help in further work to optimize transit vehicle size and stops distances along each single bus route.

closed bus routes. Transit passengers, in many cases, deal with overlapping bus routes with some routes sharing common sections and stops. Passenger assignment problem is a major task in frequency setting of bus service which aims to minimize passengers and operator costs. In this work, mixed integer mathematical formulation based on passenger choice problem is developed to track each proportion of passengers’ in selecting bus routes for -0- and -1- trips transfer. The proposed model would help for a given transit network and total bus fleet size to minimize network total travel time. It would optimally distribute frequency among bus routes, regarding passengers’ interests in selecting bus routes. It differs from traditional models, since it helps in tracking different users while they are moving on the network. Numerical examples are given to clarify the proposed mathematical formulation. Circular bus routes operational performance is tested using Mandl’s network benchmark problem. Genetic Algorithm has been implemented with Matlab language in solution procedure. Comparing results with previous work indicates that circular bus routes manage in minimizing average user travel time for the same operator cost. The results from this study would help in further work to optimize transit vehicle size and stops distances along each single bus route.