The effect of sinter basicity on softening-melting behaviors of mixed burden made from chromium-bearing vanadium-titanium magnetite(Cr-V-Ti magnetite) was investigated and the function mechanism was simultaneously ana...The effect of sinter basicity on softening-melting behaviors of mixed burden made from chromium-bearing vanadium-titanium magnetite(Cr-V-Ti magnetite) was investigated and the function mechanism was simultaneously analyzed.The results show that with increasing sinter basicity from 1.71 to 2.36,the softening interval tends to increase from 149.3 ℃ to 181.7 ℃while the melting interval tends to decrease from 178.0 ℃ to 136.7 ℃.The location of cohesive zone moves downwards firstly and then ascends slightly,but the cohesive zone becomes thinner.The softening-melting characteristic value becomes small,which indicates that the permeability of burden column is improved.The dripping ratio of mixed burden tends to increase firstly and then decrease,which comes to the highest value of 74.50%when the sinter basicity is 2.13.The content and the recovery of V and Cr in dripping iron are all increased.The generation amount of components with high melting point in slag becomes little with the increase of sinter basicity,which could improve the permeability of mixed burden.Taking softening-melting behaviors of mixed burden and recovery of valuable elements into account,the proper sinter basicity is no less than 2.13 for smelting mixed burden made from Cr-V-Ti magnetite in blast furnace.展开更多
Functionally graded material(FGM)can tailor properties of components such as wear resistance,corrosion resistance,and functionality to enhance the overall performance.The selective laser melting(SLM)additive manufactu...Functionally graded material(FGM)can tailor properties of components such as wear resistance,corrosion resistance,and functionality to enhance the overall performance.The selective laser melting(SLM)additive manufacturing highlights the capability in manufacturing FGMs with a high geometrical complexity and manufacture flexibility.In this work,the 316L/CuSn10/18Ni300/CoCr four-type materials FGMs were fabricated using SLM.The microstructure and properties of the FGMs were investigated to reveal the effects of SLM processing parameters on the defects.A large number of microcracks were found at the 316L/CuSn10 interface,which initiated from the fusion boundary of 316L region and extended along the building direction.The elastic modulus and nano-hardness in the 18Ni300/CoCr fusion zone decreased significantly,less than those in the 18Ni300 region or the CoCr region.The iron and copper elements were well diffused in the 316L/CuSn10 fusion zone,while elements in the CuSn10/18Ni300 and the 18Ni300/CoCr fusion zones showed significantly gradient transitions.Compared with other regions,the width of the CuSn10/18Ni300 interface and the CuSn10 region expand significantly.The mechanisms of materials fusion and crack generation at the 316L/CuSn10 interface were discussed.In addition,FGM structures without macro-crack were built by only altering the deposition subsequence of 316L and CuSn10,which provides a guide for the additive manufacturing of FGM structures.展开更多
By establishing the numerical model in the vertical plane and the similar model in the horizontal plane of gas flow in goaf, the influence of high drainage roadway or drilling on the gas seepage field was analyzed, an...By establishing the numerical model in the vertical plane and the similar model in the horizontal plane of gas flow in goaf, the influence of high drainage roadway or drilling on the gas seepage field was analyzed, and the extraction mechanism was clarified. On this basis, the academic thought of directional long drilling group instead of high drainage roadway was put forward. And then using complex function theory, the permeation mechanical model of drilling group with circle distribution in the mining-induced fracture zone was established to explore the coupling relationship between the drilling quantity, extraction volume and the equivalent extraction rate of single drilling. Finally, combined with the concrete geological production conditions, the main parameters of directional long drilling group were determined. The distance between the drilling group center and the air-return roadway is 24 m, the height is 18 m, and the three drillings are in an approximate equilateral triangle distribution with a space of 8 m. The equivalent extraction square is 4.15 m2. It is shown that the effect of directional long drilling group is evident. The gas content in the upper comer is controlled below 0.95%, the content in the tail roadway is kept below the alarm value, and the content is over 50% in the drill, realizing the secure and effective extraction of coal and gas.展开更多
现有目标检测算法对背景复杂下小交通标志的检测效果并不理想。为此,提出了一种基于归一化通道注意力机制YOLOv7的交通标志检测算法(YOLOv7 based on normalized channel attention mechanism,YOLOv7-NCAM)。为了使YOLOv7-NCAM模型具有...现有目标检测算法对背景复杂下小交通标志的检测效果并不理想。为此,提出了一种基于归一化通道注意力机制YOLOv7的交通标志检测算法(YOLOv7 based on normalized channel attention mechanism,YOLOv7-NCAM)。为了使YOLOv7-NCAM模型具有像素级建模能力,提高它对小目标交通标志特征的提取能力,YOLOv7-NCAM算法使用FReLU激活函数构建了DBF和CBF两种卷积层,并用它们来组建模型的Backbone模块和Neck模块;提出一种归一化通道注意力机制(normalized channel attention mechanism,NCAM)并加入Head模块中。通过与整体网络一起训练,得到归一化(batch normalization,BN)缩放因子,利用缩放因子算出各个通道的权重因子,提升网络对交通标志特征的表达能力,从而使YOLOv7-NCAM网络模型能够集中关注检测目标交通标志。通过在CCTSDB-2021交通标志检测数据集上的测试,与YOLOv7网络模型对比结果表明,YOLOv7-NCAM算法对背景复杂下小交通标志的检测各项指标均有明显提高:准确率(precision,P)达到91.5%,比原网络高出9.5个百分点;召回率(recall,R)达到85.9%,比原网络高出5.7个百分点;均值平均精度(mean average precision,mAP)达到了91.4%,比原网络高出4.7个百分点。与现有的交通标志检测算法相比,YOLOv7-NCAM算法的检测准确率也有提高,且检测速度48.3 FPS,能满足实时需求。展开更多
基金Project(51574067)supported by the National Natural Science Fundation of ChinaProjects(2012AA062302,2012AA062304)supported by the National High Technology Research and Development Program of ChinaProject(N110202001)supported by the Fundamental Research Funds for the Central Universities of China
文摘The effect of sinter basicity on softening-melting behaviors of mixed burden made from chromium-bearing vanadium-titanium magnetite(Cr-V-Ti magnetite) was investigated and the function mechanism was simultaneously analyzed.The results show that with increasing sinter basicity from 1.71 to 2.36,the softening interval tends to increase from 149.3 ℃ to 181.7 ℃while the melting interval tends to decrease from 178.0 ℃ to 136.7 ℃.The location of cohesive zone moves downwards firstly and then ascends slightly,but the cohesive zone becomes thinner.The softening-melting characteristic value becomes small,which indicates that the permeability of burden column is improved.The dripping ratio of mixed burden tends to increase firstly and then decrease,which comes to the highest value of 74.50%when the sinter basicity is 2.13.The content and the recovery of V and Cr in dripping iron are all increased.The generation amount of components with high melting point in slag becomes little with the increase of sinter basicity,which could improve the permeability of mixed burden.Taking softening-melting behaviors of mixed burden and recovery of valuable elements into account,the proper sinter basicity is no less than 2.13 for smelting mixed burden made from Cr-V-Ti magnetite in blast furnace.
基金Project(2020B090922002)supported by Guangdong Provincial Key Field Research and Development Program,ChinaProjects(51875215,52005189)supported by the National Natural Science Foundation of ChinaProject(2019B1515120094)supported by Guangdong Provincial Basic and Applied Basic Research Fund,China。
文摘Functionally graded material(FGM)can tailor properties of components such as wear resistance,corrosion resistance,and functionality to enhance the overall performance.The selective laser melting(SLM)additive manufacturing highlights the capability in manufacturing FGMs with a high geometrical complexity and manufacture flexibility.In this work,the 316L/CuSn10/18Ni300/CoCr four-type materials FGMs were fabricated using SLM.The microstructure and properties of the FGMs were investigated to reveal the effects of SLM processing parameters on the defects.A large number of microcracks were found at the 316L/CuSn10 interface,which initiated from the fusion boundary of 316L region and extended along the building direction.The elastic modulus and nano-hardness in the 18Ni300/CoCr fusion zone decreased significantly,less than those in the 18Ni300 region or the CoCr region.The iron and copper elements were well diffused in the 316L/CuSn10 fusion zone,while elements in the CuSn10/18Ni300 and the 18Ni300/CoCr fusion zones showed significantly gradient transitions.Compared with other regions,the width of the CuSn10/18Ni300 interface and the CuSn10 region expand significantly.The mechanisms of materials fusion and crack generation at the 316L/CuSn10 interface were discussed.In addition,FGM structures without macro-crack were built by only altering the deposition subsequence of 316L and CuSn10,which provides a guide for the additive manufacturing of FGM structures.
基金Project(50834005) supported by the National Natural Science Foundation of ChinaProject(2010QZ06) supported by the Fundamental Research Funds for the Central Universities of China
文摘By establishing the numerical model in the vertical plane and the similar model in the horizontal plane of gas flow in goaf, the influence of high drainage roadway or drilling on the gas seepage field was analyzed, and the extraction mechanism was clarified. On this basis, the academic thought of directional long drilling group instead of high drainage roadway was put forward. And then using complex function theory, the permeation mechanical model of drilling group with circle distribution in the mining-induced fracture zone was established to explore the coupling relationship between the drilling quantity, extraction volume and the equivalent extraction rate of single drilling. Finally, combined with the concrete geological production conditions, the main parameters of directional long drilling group were determined. The distance between the drilling group center and the air-return roadway is 24 m, the height is 18 m, and the three drillings are in an approximate equilateral triangle distribution with a space of 8 m. The equivalent extraction square is 4.15 m2. It is shown that the effect of directional long drilling group is evident. The gas content in the upper comer is controlled below 0.95%, the content in the tail roadway is kept below the alarm value, and the content is over 50% in the drill, realizing the secure and effective extraction of coal and gas.
文摘现有目标检测算法对背景复杂下小交通标志的检测效果并不理想。为此,提出了一种基于归一化通道注意力机制YOLOv7的交通标志检测算法(YOLOv7 based on normalized channel attention mechanism,YOLOv7-NCAM)。为了使YOLOv7-NCAM模型具有像素级建模能力,提高它对小目标交通标志特征的提取能力,YOLOv7-NCAM算法使用FReLU激活函数构建了DBF和CBF两种卷积层,并用它们来组建模型的Backbone模块和Neck模块;提出一种归一化通道注意力机制(normalized channel attention mechanism,NCAM)并加入Head模块中。通过与整体网络一起训练,得到归一化(batch normalization,BN)缩放因子,利用缩放因子算出各个通道的权重因子,提升网络对交通标志特征的表达能力,从而使YOLOv7-NCAM网络模型能够集中关注检测目标交通标志。通过在CCTSDB-2021交通标志检测数据集上的测试,与YOLOv7网络模型对比结果表明,YOLOv7-NCAM算法对背景复杂下小交通标志的检测各项指标均有明显提高:准确率(precision,P)达到91.5%,比原网络高出9.5个百分点;召回率(recall,R)达到85.9%,比原网络高出5.7个百分点;均值平均精度(mean average precision,mAP)达到了91.4%,比原网络高出4.7个百分点。与现有的交通标志检测算法相比,YOLOv7-NCAM算法的检测准确率也有提高,且检测速度48.3 FPS,能满足实时需求。
