As one of the basic inventory cost models, the （Q, τ）inventory cost model of dual suppliers with random procurement lead time is mostly formulated by using the concepts of ＂effective lead time＂ and ＂lead time de...As one of the basic inventory cost models, the （Q, τ）inventory cost model of dual suppliers with random procurement lead time is mostly formulated by using the concepts of ＂effective lead time＂ and ＂lead time demand＂, which may lead to an imprecise inventory cost. Through the real-time statistic of the inventory quantities, this paper considers the precise （Q, τ） inventory cost model of dual supplier procurement by using an infinitesimal dividing method. The traditional modeling method of the inventory cost for dual supplier procurement includes complex procedures. To reduce the complexity effectively, the presented method investigates the statistics properties in real-time of the inventory quantities with the application of the infinitesimal dividing method. It is proved that the optimal holding and shortage costs of dual supplier procurement are less than those of single supplier procurement respectively. With the assumption that both suppliers have the same distribution of lead times, the convexity of the cost function per unit time is proved. So the optimal solution can be easily obtained by applying the classical convex optimization methods. The numerical examples are given to verify the main conclusions.展开更多
Based on the characteristics of fractures in naturally fractured reservoir and a discrete-fracture model, a fracture network numerical well test model is developed. Bottom hole pressure response curves and the pressur...Based on the characteristics of fractures in naturally fractured reservoir and a discrete-fracture model, a fracture network numerical well test model is developed. Bottom hole pressure response curves and the pressure field are obtained by solving the model equations with the finite-element method. By analyzing bottom hole pressure curves and the fluid flow in the pressure field, seven flow stages can be recognized on the curves. An upscaling method is developed to compare with the dual-porosity model （DPM）. The comparisons results show that the DPM overestimates the inter-porosity coefficient ）, and the storage factor w. The analysis results show that fracture conductivity plays a leading role in the fluid flow. Matrix permeability influences the beginning time of flow from the matrix to fractures. Fractures density is another important parameter controlling the flow. The fracture linear flow is hidden under the large fracture density. The pressure propagation is slower in the direction of larger fracture density.展开更多
为研究割草除根松土一体式刀片结构参数对其作业性能的影响,基于离散元法(discrete element method,EDEM)软件建立三维离散元仿真模型,模拟刀片在刨土作业过程中的破土效果。通过单因素试验分析前进速度、旋转速度及刀片倾角对破土率的...为研究割草除根松土一体式刀片结构参数对其作业性能的影响,基于离散元法(discrete element method,EDEM)软件建立三维离散元仿真模型,模拟刀片在刨土作业过程中的破土效果。通过单因素试验分析前进速度、旋转速度及刀片倾角对破土率的影响规律,进一步采用Box-Behnken正交试验结合响应面分析法建立破土率预测模型并进行参数优化。正交试验结果表明,刀片倾角是影响破土率的主要因素,其次为旋转速度,三因素交互作用亦具有显著性。在最优参数组合下,前进速度1.39 m/s、旋转速度107 rad/s、刀片倾角4.7°,破土率达到78.3%。研究结果为山地割草除根松土装置的结构设计与参数配置提供理论依据和实践指导。展开更多
The final microstructure of DP and TRIP assisted steels can evolve after hot working (hot rolling) or during post heat treatment process. In the formation of the final structure a number of different technological par...The final microstructure of DP and TRIP assisted steels can evolve after hot working (hot rolling) or during post heat treatment process. In the formation of the final structure a number of different technological parameters have important roles, e.g. end temperature of rolling, cooling rates, temperature of intercritical annealing, etc. As a result of the individual factors and their combinations a lot of product technology routes are feasible. The effect of the different combinations of these technological parameters on the microstructure can be mapped by the special Jominy end-quench test (so called intercritical Jominy end-quench test) described in this paper. Unlike the traditional Jominy test, in this case there is a partial austenizing between A! and A3 temperatures which results in a given amount of ferrite in the microstructure before quenching. The method developed can be applied for mapping DP and TRIP assisted steels’ microstructure in a wide range of technological parameters. The analysis of measured and calculated data can help us find the technological parameters optimal from the microstructural point of view.展开更多
基金supported by the National High Technology Research and Development Program of China(863 Program)(2007AA04Z102)the National Natural Science Foundation of China(6087407160574077).
文摘As one of the basic inventory cost models, the （Q, τ）inventory cost model of dual suppliers with random procurement lead time is mostly formulated by using the concepts of ＂effective lead time＂ and ＂lead time demand＂, which may lead to an imprecise inventory cost. Through the real-time statistic of the inventory quantities, this paper considers the precise （Q, τ） inventory cost model of dual supplier procurement by using an infinitesimal dividing method. The traditional modeling method of the inventory cost for dual supplier procurement includes complex procedures. To reduce the complexity effectively, the presented method investigates the statistics properties in real-time of the inventory quantities with the application of the infinitesimal dividing method. It is proved that the optimal holding and shortage costs of dual supplier procurement are less than those of single supplier procurement respectively. With the assumption that both suppliers have the same distribution of lead times, the convexity of the cost function per unit time is proved. So the optimal solution can be easily obtained by applying the classical convex optimization methods. The numerical examples are given to verify the main conclusions.
基金Project supported by the National Natural Science Foundation of China(No.5140232)the National Science and Technology Major Project(No.2011ZX05038003)the China Postdoctoral Science Foundation(No.2014M561074)
文摘Based on the characteristics of fractures in naturally fractured reservoir and a discrete-fracture model, a fracture network numerical well test model is developed. Bottom hole pressure response curves and the pressure field are obtained by solving the model equations with the finite-element method. By analyzing bottom hole pressure curves and the fluid flow in the pressure field, seven flow stages can be recognized on the curves. An upscaling method is developed to compare with the dual-porosity model （DPM）. The comparisons results show that the DPM overestimates the inter-porosity coefficient ）, and the storage factor w. The analysis results show that fracture conductivity plays a leading role in the fluid flow. Matrix permeability influences the beginning time of flow from the matrix to fractures. Fractures density is another important parameter controlling the flow. The fracture linear flow is hidden under the large fracture density. The pressure propagation is slower in the direction of larger fracture density.
文摘为研究割草除根松土一体式刀片结构参数对其作业性能的影响,基于离散元法(discrete element method,EDEM)软件建立三维离散元仿真模型,模拟刀片在刨土作业过程中的破土效果。通过单因素试验分析前进速度、旋转速度及刀片倾角对破土率的影响规律,进一步采用Box-Behnken正交试验结合响应面分析法建立破土率预测模型并进行参数优化。正交试验结果表明,刀片倾角是影响破土率的主要因素,其次为旋转速度,三因素交互作用亦具有显著性。在最优参数组合下,前进速度1.39 m/s、旋转速度107 rad/s、刀片倾角4.7°,破土率达到78.3%。研究结果为山地割草除根松土装置的结构设计与参数配置提供理论依据和实践指导。
基金support of Hungarian Ministry of Education and TET Foundation(CHN-25/03 China-Hungary)is greatly acknowledged.
文摘The final microstructure of DP and TRIP assisted steels can evolve after hot working (hot rolling) or during post heat treatment process. In the formation of the final structure a number of different technological parameters have important roles, e.g. end temperature of rolling, cooling rates, temperature of intercritical annealing, etc. As a result of the individual factors and their combinations a lot of product technology routes are feasible. The effect of the different combinations of these technological parameters on the microstructure can be mapped by the special Jominy end-quench test (so called intercritical Jominy end-quench test) described in this paper. Unlike the traditional Jominy test, in this case there is a partial austenizing between A! and A3 temperatures which results in a given amount of ferrite in the microstructure before quenching. The method developed can be applied for mapping DP and TRIP assisted steels’ microstructure in a wide range of technological parameters. The analysis of measured and calculated data can help us find the technological parameters optimal from the microstructural point of view.
