Mixed coordination mechanisms for scheduling games on hierarchical machines

In this paper, we study scheduling games under mixed coordination mechanisms on hierarchical machines. The two scheduling policies involved are ‐ and ‐, where ‐ (resp., ‐) policy sequences jobs in nondecreasing order of their hierarchies, and jobs of the same hierarchy in nonincreasing (resp., nondecreasing) order of their processing times. We first show the existence of a Nash equilibrium. Then we present the price of anarchy and the price of stability for the games with social costs of minimizing the makespan and maximizing the minimum machine load. All the bounds given in this paper are tight.     

Numerical investigation on optimization of thermal analysis due to immersion of hybrid nanostructures in a fluid of shear dependent viscosity using the finite element method

This article considers the dispersion of hybrid and mono nanoparticles in a fluid with viscosity (Williamson) dependent on shear rate, over a heated surface moving with nonuniform velocity and exposed to a magnetic field in the presence of an applied current. Extensive modeling leads to complex coupled mathematical models that are solved numerically via the finite element method (FEM). Convergent simulations are run to investigate the role of parameters on the dynamics of flow fields. The magnetic field intensity plays a role in controlling the magnetohydrodynamic boundary layer thickness (BLT) and thermal radiation controls the thickness of thermal boundary layers (TBL). However, the magnetic field intensity is responsible for an increase in BLT. In contrast to this, thermal radiation plays a role in controlling the thickness of the TBL. The impact of shear rate dependent viscosity on velocity is remarkable for both fluids. The motion of both of the fluids slows down when viscosity varies as a function of shear rate. Viscosity depending on the shear rate has a significant impact on wall shear stress. It is observed from simulations that wall shear increases when the parameters appearing in the model for shear rate dependent viscosity are increased. However, this increase in wall shear stress associated with a hybrid nanofluid is greater than the increase in wall shear stress associated with a mono nanofluid.     

低碳环境下钢铁企业燃气系统动态平衡调度仿真

在“节能减排、降本增效”的大背景下,从碳素流视角切入,在煤气介质预测基础上,建立了0-1混合线性规划模型,以能源成本和碳交易成本总和最小化为目标,研究钢铁行业副产煤气生产调度问题。采用基于遗传算法的动态迭代调度算法,通过混合交叉算子和平均变异算子提高遗传算法局部搜索能力,并以国内某大型钢铁企业为仿真对象进行系统仿真,结果表明:混合煤气柜可以根据煤气产耗特点调整存储量,并保证存储量在合理范围内;调节用户会起到一定的缓冲作用,可以根据某种副产煤气的产耗特点响应增加或减少该种煤气的消耗量;当某种副产煤气严重不足时,固定消耗用户会根据优先级响应停调,以满足生产需求。可见副产煤气的优化调度应用可以为中国钢铁行业的低碳发展和节能减排提供技术支撑。     

A robust mixed integer linear programming framework for underground cut-and-fill mining production scheduling

ABSTRACT

A review of general optimization studies that have been proposed for underground mining shows that previous works lack flexibility, operability and practicality in relation to cut-and-fill mining production scheduling. This paper presents a robust mixed integer linear programming (MILP) formulation for underground cut-and-fill mining. The objective function of the model is to maximize the net present value (NPV) of the operation while meeting all mining and processing operational and technical constraints. The MILP model features stope development and extraction sequencing constraints, mining and processing tonnage fluctuation constraints, and extraction duration and active levels control constraints. These features make the model more practical and expandable. The MILP model is verified and validated with two case studies from an existing mine and the results are compared with the actual mining strategy. The comparison shows a 9% to 17% improved NPV in both case studies resulting from mining higher grades and processing less tonnes thereby generating a better cash flow.     

对当前监理工作的认识

对当前监理工作存在的问题进行了分析,指出了监理工作的主要任务、监理单位的权利及当前监理工作应解决的问题。     

Production scheduling under uncertainty of an open-pit mine using Lagrangian relaxation and branch-and-cut algorithm

ABSTRACT

The life-of-mine optimization of open pit mine production scheduling under geological uncertainty is a computationally intensive process. Production scheduling determines the optimal extraction sequence by maximizing net present value (NPV). In this paper, an algorithm is proposed to schedule an open pit mine under geological uncertainty, where instead of solving the whole problem at once, the production schedule is generated by sequentially solving sub-problems. The sub-gradient method is used to generate the upper bound solution of a Lagrangian relaxed sub-problem. If the upper bound relaxed solution is infeasible, a mixed integer programming is applied to the latter solution. The algorithm is validated by solving six problems and is compared to the linear relaxation of the original production scheduling problem. The results show that the proposed algorithm generates a solution that is very close to optimal, with less than a 3% optimality gap. An application at a copper mine, where geological uncertainty is quantified with geostatistical simulations of the related orebody, shows that all constraints are satisfied and an 11% higher NPV is generated when compared to the corresponding deterministic equivalent of the proposed approach, while a 26% higher NPV is generated compared to a common conventional industry approach.     

基于局部路径重连的多星测控调度遗传交叉算子

为提高多星测控调度问题简单遗传算法的搜索精度,设计一种基于局部分层路径搜索的交叉算子(local layering path-relinking crossover operator,LLPRCO)。分析多星测控调度问题的遗传算法编码特点,得出解空间的复杂性和基因间较弱的相关性。借鉴路径重连的思想,利用构成初始解和引导解要素的差异性,构建从初始解出发的分层搜索邻域,将邻域中满足模型约束的解作为交叉的结果,并创建2个仿真场景进行验证。仿真结果表明,该交叉算子与具备一定随机特性的交叉算子混合使用能明显提高遗传算法对问题的求解性能。     

灰色时效模型及在基坑锚拉墙位移预测中的应用

针对岩土工程的灰色理论，单纯从可测位移建立可预测的模型，未考虑工程荷载影响．在分析岩土流变模型的基础上，建立了反映岩土工程荷载与位移的时效关系的灰色流变模型GRM（m，n），并提出了采用最小二乘辨识模型的方法．将该模型辨识应用于辨识基坑锚拉墙中锚座位移随荷载变化时效关系并用于预测后期锚座位移，取得理想效果，验证了方法的可行性．     

基于GIS的管网事故状态调度决策系统

结合我国城市供水运行管理现状，将计算机技术、信息技术和决策支持系统理论引入城市供水运行优化调度中，建立了基于GIS的供水管网事故状态决策支持系统，详述了其结构与功能。     

钢结构工程抗力时变模型的构建与验证

提出了一种全新的钢结构抗力时变模型,对多种影响因素在模型中的表述方式与初步取值范围展开了探讨。采用通用有限元程序提供的APDL语言将结构分析和其PDS模块的统计分析能力相结合,实现了基于蒙特卡罗（the Monte Carlo）有限元模拟方法的时变可靠度计算,并与非时变条件可靠性计算结果做出对比。经算例验证,结果表明：考虑抗力时变后,时间因素对结构的可靠性影响显著;同时文中提出的钢结构抗力时变函数在形式上是基本合理可行的。