A mathematical model for open pit mine production scheduling with Grade Engineering and stockpiling

This paper presents the development and implementation of an innovative mixed integer programming based mathematical model for an open pit mining operation with Grade Engineering framework.Grade Engineering comprises a range of coarse-separation based pre-processing techniques that separate the desirable(i.e.high-grade)and undesirable(i.e.low-grade or uneconomic)materials and ensure the delivery of only selected quantity of high quality(or high-grade)material to energy,water,and cost-intensive processing plant.The model maximizes the net present value under a range of operational and processing constraints.Given that the proposed model is computationally complex,the authors employ a data preprocessing procedure and then evaluate the performance of the model at several practical instances using computation time,optimality gap,and the net present value as valid measures.In addition,a comparison of the proposed and traditional(without Grade Engineering)models reflects that the proposed model outperforms the traditional formulation.

High-dielectric-constant nanograin BaTiO_(3)-based ceramics for ultra-thin layer multilayer ceramic capacitors via grain grading engineering

Four BT-based ceramic samples were prepared using a grain grading approach.The bigger-grained(~100 nm)and smaller-grained(~70 nm)BaTiO_(3)(BT)powders were mixed.The smaller-grained BT powder controlled the average grain size and guaranteed the reliability,while the bigger-grained powder enhanced the dielectric constant.Various percentages of bigger-grained BT powder were introduced to balance the average grain size and the dielectric constant.As the proportion of bigger grains increased,the dielectric constant(εr)improved significantly.The room-temperatureεr of 25%bigger-grain mixed BT(2623)was~50%higher than that of the sample with a similar average grain size without grain grading.The ceramic mixed with 15%bigger-grained BT showed comprehensive dielectric performance,which met the EIA X5R standard and provided a considerableεr of 1841 along with a low dielectric loss of 0.78%.Notably,the average grain size was 90 nm,which favors the applications in ultra-thin multilayer ceramic capacitors.