Large cutting height fully mechanized top-coal caving is a new mining method that improves recovery ratio and single-pass production. It also allows safe and efficient mining. A rational cutting height is one key para...Large cutting height fully mechanized top-coal caving is a new mining method that improves recovery ratio and single-pass production. It also allows safe and efficient mining. A rational cutting height is one key parameter of this technique. Numerical simulation and a granular-media model experiment were used to analyze the effect of cutting height on the rock pressure of a fully mechanized top-coal caving work face. The recovery ratio was also studied. As the cutting height increases the top-coal thickness is reduced. Changing the ratio of cutting to drawing height intensifies the face pressure and the top-coal shattering. A maximum cutting height exists under a given set of conditions due to issues with surrounding rock-mass control. An increase in cutting height makes the top-coal cave better and the recovery ratio when drawing top-coal is then improved. A method of adjusting the face rock pressure is presented. Changing the cutting to drawing height ratio is the technique used to control face rock pressure. The recovery ratio when cutting coal exceeds that when caving top-coal so the face recovery ratio may be improved by over sizing the cutting height and increasing the top-coal drawing ratio. An optimum ratio of cutting to drawing height exists that maximizes the face recovery ratio. A rational cutting height is determined by comprehensively considering the surrounding rock-mass control and the recovery ratio. At the same time increasing the cutting height can improve single pass mining during fully mechanized top-coal caving.展开更多
针对R-cut(Ratio cut)边缘检测分割模型对高分辨率遥感影像分割时存在过分割和模糊边缘敏感性问题,提出了一种多尺度R-cut(Multi-scale ratio cut,MSR-cut)的遥感影像边缘检测分割方法。首先,采用形态重建的分水岭分割算法对影像过分割...针对R-cut(Ratio cut)边缘检测分割模型对高分辨率遥感影像分割时存在过分割和模糊边缘敏感性问题,提出了一种多尺度R-cut(Multi-scale ratio cut,MSR-cut)的遥感影像边缘检测分割方法。首先,采用形态重建的分水岭分割算法对影像过分割,形成多个超像素区域;然后计算并提取影像各个区域的纹理特征信息熵值、光谱特征与邻域均值差分归一化值,分别进行同质性和异质性的有效衡量;并构建评价函数获取最优分割尺度,对这些超像素区域进行初步合并,得到影像的粗分割结果;最后结合各地物的边界权重信息,从全局角度用R-cut的方法对粗分割结果进一步合并,完成对影像的精细分割,生成最终的分割结果。实验选取5个不同场景的高分辨率遥感影像,采用定性和定量两种方法对比分析本文方法与传统R-cut边缘检测分割、Spectral-Rcut边缘检测分割和Textured-Rcut边缘检测分割方法。实验结果表明,MSR-cut边缘检测分割方法能够有效提高分割精度,增强噪声鲁棒性,可取得较好的分割视觉效果。展开更多
Recently, laser cutting technologies begin to use for manufacturing mechanical parts of Inconel super-alloy sheet due to difficulties of machining of the Inconel material as a results of its extremely tough nature. Th...Recently, laser cutting technologies begin to use for manufacturing mechanical parts of Inconel super-alloy sheet due to difficulties of machining of the Inconel material as a results of its extremely tough nature. The objective of this work is to investigate the influence of cutting parameters on surface characteristics of the cut section in the cutting of Inconel 718 super-alloy sheet using CW Nd:YAG laser through laser cutting experiments. Normal cutting experiments were performed using a laser cutting system with six-axis controlled automatic robot and auto-tracking system of the focal distance. From the results of the experiments, the effects of the cutting parameters on the surface roughness, the striation formation and the microstructure of the cut section were examined. In addition, an optimal cutting condition, at which the surface roughness is minimized and both the delayed cutting phenomenon and the micro-cracking are not initiated, is estimated to improve both the part quality and the cutting efficiency.展开更多
This paper describes the application of orthogonal test design coupled with non-linear regression analysis to optimize abrasive suspension jet （AS J） cutting process and construct its cutting model. Orthogonal test ...This paper describes the application of orthogonal test design coupled with non-linear regression analysis to optimize abrasive suspension jet （AS J） cutting process and construct its cutting model. Orthogonal test design is applied to cutting stainless steel. Through range analysis on experiment results, the optimal process conditions for the cutting depth and the kerr ratio of the bottom width to the top width can be determined. In addition, the analysis of ranges and variances are all employed to identify various factors： traverse rate, working pressure, nozzle diameter, standoff distance which denote the importance order of the cutting parameters affecting cutting depth and the kerf ratio of the bottom width to the top width. ~rthermore, non-linear regression analysis is used to establish the mathematical models of the cutting parameters based on the cutting depth and the kerr ratio. Finally, the verification experiments of cutting parameters＇ effect on cutting performance, which show that optimized cutting parameters and cutting model can significantly improve the prediction of the cutting ability and quality of ASJ.展开更多
Let G be a graph and(V_(i),V_(2),...,V_(e))be a k-partition of G.For 1≤i<j≤k,the ratio of(V_(i),V_(j)),denoted by R(V_(i),V_(j)),is e(V_(i),V_(j))/(|V_(i)||V_(j)|),where e(V_(i),V_(j))is the number of crossing ed...Let G be a graph and(V_(i),V_(2),...,V_(e))be a k-partition of G.For 1≤i<j≤k,the ratio of(V_(i),V_(j)),denoted by R(V_(i),V_(j)),is e(V_(i),V_(j))/(|V_(i)||V_(j)|),where e(V_(i),V_(j))is the number of crossing edges.The minimum k-ratio of G,denoted by R_(k)(G),is the minimumΣ_(i)≤i≤k R(V_(i),V_(j))overall k-partions(V_(1),V_(2),..V_(k))of G.Let R(G)=R_(2)(G).The ratio cut problem,posed by Wei and Cheng,and independently by Leighton and Rao,is an extension of the min-cut problem and has important applications in CAD.It is easy to see that Rk(G)is closely related to the density d(G)of a graph G.In this paper,we mainly give some results on Rk(G)with respect to d(G).First,we show that R_(k)(G)≤(2^(K))(1+o(1)d(G)for graphs G and Rk(G)≤(k-1)(1+o(1)d(G)for sparse graphs G.Then,we give some upper and lower bounds on R(G).In particular,we show R(G)≤4/(n-3)for every planar graph G with n≥4 vertices.At last,we consider the random graph G(n,p)and show that R(G(n,p))can be determined asymptotically almost surely if p≥C log n/n for some constant C>0.展开更多
基金Financial support for this work, provided by the National Basic Research Program of China (No.2007CB209400)the National Natural Science Foundation of China (No.51004104)
文摘Large cutting height fully mechanized top-coal caving is a new mining method that improves recovery ratio and single-pass production. It also allows safe and efficient mining. A rational cutting height is one key parameter of this technique. Numerical simulation and a granular-media model experiment were used to analyze the effect of cutting height on the rock pressure of a fully mechanized top-coal caving work face. The recovery ratio was also studied. As the cutting height increases the top-coal thickness is reduced. Changing the ratio of cutting to drawing height intensifies the face pressure and the top-coal shattering. A maximum cutting height exists under a given set of conditions due to issues with surrounding rock-mass control. An increase in cutting height makes the top-coal cave better and the recovery ratio when drawing top-coal is then improved. A method of adjusting the face rock pressure is presented. Changing the cutting to drawing height ratio is the technique used to control face rock pressure. The recovery ratio when cutting coal exceeds that when caving top-coal so the face recovery ratio may be improved by over sizing the cutting height and increasing the top-coal drawing ratio. An optimum ratio of cutting to drawing height exists that maximizes the face recovery ratio. A rational cutting height is determined by comprehensively considering the surrounding rock-mass control and the recovery ratio. At the same time increasing the cutting height can improve single pass mining during fully mechanized top-coal caving.
文摘针对R-cut(Ratio cut)边缘检测分割模型对高分辨率遥感影像分割时存在过分割和模糊边缘敏感性问题,提出了一种多尺度R-cut(Multi-scale ratio cut,MSR-cut)的遥感影像边缘检测分割方法。首先,采用形态重建的分水岭分割算法对影像过分割,形成多个超像素区域;然后计算并提取影像各个区域的纹理特征信息熵值、光谱特征与邻域均值差分归一化值,分别进行同质性和异质性的有效衡量;并构建评价函数获取最优分割尺度,对这些超像素区域进行初步合并,得到影像的粗分割结果;最后结合各地物的边界权重信息,从全局角度用R-cut的方法对粗分割结果进一步合并,完成对影像的精细分割,生成最终的分割结果。实验选取5个不同场景的高分辨率遥感影像,采用定性和定量两种方法对比分析本文方法与传统R-cut边缘检测分割、Spectral-Rcut边缘检测分割和Textured-Rcut边缘检测分割方法。实验结果表明,MSR-cut边缘检测分割方法能够有效提高分割精度,增强噪声鲁棒性,可取得较好的分割视觉效果。
基金Project supported by a grant-in-aid of Regional Innovation Center (RIC),New Technology Development and Research Center of Laser Application in Chosun University,Korea
文摘Recently, laser cutting technologies begin to use for manufacturing mechanical parts of Inconel super-alloy sheet due to difficulties of machining of the Inconel material as a results of its extremely tough nature. The objective of this work is to investigate the influence of cutting parameters on surface characteristics of the cut section in the cutting of Inconel 718 super-alloy sheet using CW Nd:YAG laser through laser cutting experiments. Normal cutting experiments were performed using a laser cutting system with six-axis controlled automatic robot and auto-tracking system of the focal distance. From the results of the experiments, the effects of the cutting parameters on the surface roughness, the striation formation and the microstructure of the cut section were examined. In addition, an optimal cutting condition, at which the surface roughness is minimized and both the delayed cutting phenomenon and the micro-cracking are not initiated, is estimated to improve both the part quality and the cutting efficiency.
基金supported by the Science and Technology Development Foundation of Shanghai Municipal Science and Technology Commission (Grant No.037252022)
文摘This paper describes the application of orthogonal test design coupled with non-linear regression analysis to optimize abrasive suspension jet （AS J） cutting process and construct its cutting model. Orthogonal test design is applied to cutting stainless steel. Through range analysis on experiment results, the optimal process conditions for the cutting depth and the kerr ratio of the bottom width to the top width can be determined. In addition, the analysis of ranges and variances are all employed to identify various factors： traverse rate, working pressure, nozzle diameter, standoff distance which denote the importance order of the cutting parameters affecting cutting depth and the kerf ratio of the bottom width to the top width. ~rthermore, non-linear regression analysis is used to establish the mathematical models of the cutting parameters based on the cutting depth and the kerr ratio. Finally, the verification experiments of cutting parameters＇ effect on cutting performance, which show that optimized cutting parameters and cutting model can significantly improve the prediction of the cutting ability and quality of ASJ.
基金supported by the National Natural Science Foundation of China(No.12071077)a project of Center for Applied Mathematics of Fujian Province,and a cooperation project of HUAWEI.
文摘Let G be a graph and(V_(i),V_(2),...,V_(e))be a k-partition of G.For 1≤i<j≤k,the ratio of(V_(i),V_(j)),denoted by R(V_(i),V_(j)),is e(V_(i),V_(j))/(|V_(i)||V_(j)|),where e(V_(i),V_(j))is the number of crossing edges.The minimum k-ratio of G,denoted by R_(k)(G),is the minimumΣ_(i)≤i≤k R(V_(i),V_(j))overall k-partions(V_(1),V_(2),..V_(k))of G.Let R(G)=R_(2)(G).The ratio cut problem,posed by Wei and Cheng,and independently by Leighton and Rao,is an extension of the min-cut problem and has important applications in CAD.It is easy to see that Rk(G)is closely related to the density d(G)of a graph G.In this paper,we mainly give some results on Rk(G)with respect to d(G).First,we show that R_(k)(G)≤(2^(K))(1+o(1)d(G)for graphs G and Rk(G)≤(k-1)(1+o(1)d(G)for sparse graphs G.Then,we give some upper and lower bounds on R(G).In particular,we show R(G)≤4/(n-3)for every planar graph G with n≥4 vertices.At last,we consider the random graph G(n,p)and show that R(G(n,p))can be determined asymptotically almost surely if p≥C log n/n for some constant C>0.
