A new blasting approach of combined blastholes with different diameters is proposed to solve the problems of oversize boulders and rock toes in open-pit mine. A non-ideal detonation model and a statistical damage cons...A new blasting approach of combined blastholes with different diameters is proposed to solve the problems of oversize boulders and rock toes in open-pit mine. A non-ideal detonation model and a statistical damage constitutive model are implemented in dynamic finite element analysis to investigate the formation mechanism of oversize boulders and toes. The damage distribution and evolution process of rock blasting fragmentation is simulated, and the scheme is further optimized. Numerical analysis results showed that pocket charges and satellite blastholes can only improve bench top fragmentation, but they cannot reduce the oversize in the middle and bottom of bench as well as the toe problem. The new blasting approach of combined blastholes with different diameters can effectively reduce the oversize boulders and toes as well as the production costs.展开更多
This paper presents a novel computational procedure for the maximum dry density of mixed soils containing oversize particles.At first,the large-scale compaction test data for mixed soils are analyzed by an artificial ...This paper presents a novel computational procedure for the maximum dry density of mixed soils containing oversize particles.At first,the large-scale compaction test data for mixed soils are analyzed by an artificial neural network to determine the main factors affecting the compaction.These factors are then imposed on a genetic programming method and a new mathematical equation emerges.The new equation has more conformity with the experimental data in comparison with the previous correction methods.Besides,the mixed soil dry density is associated with most base soil and oversize fraction specifications.With regard to the sensitivity analyses,if the mixed soil contains high percentages of oversize fraction,the mixed soil composition is governed by the specification of oversized grains,such as specific gravity and the maximum grain size and by increasing these factors,the mixed soil dry density is increased.In mixed soil with a low content of oversize,the base soil specification mainly controls the compaction behavior of mixed soil.Furthermore,if the base soil is inherently compacted with greater dry density,adding the oversize slightly improves the mixed soil dry density.In contrast,adding oversized grains to the base soil with a lower dry density produces a mixed soil with greater dry density.By increasing the maximum grain size difference between the oversize fraction and base soil,the dry density of mixed soil is enhanced.展开更多
It is an honor to be the vip editor of this special issue on Current Consensus and Controversy on Male Lower Urinary Tract Symptoms(LUTS)/Benign Prostatic Hyperplasia(BPH).As the title implies,one can write on a wid...It is an honor to be the vip editor of this special issue on Current Consensus and Controversy on Male Lower Urinary Tract Symptoms(LUTS)/Benign Prostatic Hyperplasia(BPH).As the title implies,one can write on a wide range of topics related to this urological problem that is common worldwide.展开更多
Non-cohesive soils have been widely used in construction of high-speed railway for their excellent physical and mechanical properties,and the determination of maximum and minimum dry density of such soils containing o...Non-cohesive soils have been widely used in construction of high-speed railway for their excellent physical and mechanical properties,and the determination of maximum and minimum dry density of such soils containing oversize particles is an important topic.In this study,the influence of oversize particles on dry density of non-cohesive soils is investigated by packing tests.Test results show that oversize particles will make"extra"voids around their surfaces,which increase significantly if the size ratio of oversize material to matrix material is not very big.The dry density of the total material will be overestimated by Elimination Method due to the omission of the"extra"voids.Thus,a geometric model is proposed by which the"extra"voids can be taken into account,and a new oversize correction method for non-cohesive soils is developed.Test results confirm the applicability of this method on the condition of oversize fraction being less than 40%by mass.展开更多
On the evening of May 3,one day before China’s Youth Day,well-known actor He Bing made a speech on Bilibili,a videosharing platform themed around animation and games.The 52-year-old praised the younger generation,esp...On the evening of May 3,one day before China’s Youth Day,well-known actor He Bing made a speech on Bilibili,a videosharing platform themed around animation and games.The 52-year-old praised the younger generation,especially those born in the 1990s,and expressed his expectations for them.展开更多
U.S.Secretary of Commerce Gina Raimondo made a high-profile trip to China last August.There,she talked up the“enormous"Chinese market and the incredible“appetite among U.S.businesses to continue to do business&...U.S.Secretary of Commerce Gina Raimondo made a high-profile trip to China last August.There,she talked up the“enormous"Chinese market and the incredible“appetite among U.S.businesses to continue to do business"there.While no significant deals were unveiled during her visit,it did leave the impression that the White House intended to continue open dialogue and continue doing business with China.展开更多
From the media,we get the impression that celebrities and public figures recover almost instantly from pregnancy.All of this“news”may leave us questioning what a normal recovery should look and feel like.The reality...From the media,we get the impression that celebrities and public figures recover almost instantly from pregnancy.All of this“news”may leave us questioning what a normal recovery should look and feel like.The reality is it takes months for the body to recuperate from pregnancy:not only to reach pre-pregnancy weight but also to regain pre-pregnancy figure and strength.展开更多
对于17-4PH钢超大型锻件而言,其成分宏观偏析、缩孔疏松、碳化物析出、裂纹的产生以及晶粒度的大小通常难以控制,从而严重影响其力学性能和后续的产品使用。以28 t 17-4PH钢电渣锭从生产至获得成品的生产为例,从对重熔渣系设计、锻造工...对于17-4PH钢超大型锻件而言,其成分宏观偏析、缩孔疏松、碳化物析出、裂纹的产生以及晶粒度的大小通常难以控制,从而严重影响其力学性能和后续的产品使用。以28 t 17-4PH钢电渣锭从生产至获得成品的生产为例,从对重熔渣系设计、锻造工艺流程以及固溶时效热处理等重点工艺入手,优化了产品制造过程,特别通过精确控制固溶和时效工艺,在350~1050℃范围内分步加热保温固溶处理以及150~530℃范围内多次加热保温时效处理,成功控制了产品中残余奥氏体、富铜相及弥散析出相的体积分数,达到了可控的基体晶粒度,有效抑制了不利相的析出,同时显著降低了工件的内部应力及开裂风险。通过优化措施不仅保证了产品的力学性能,而且显著延长了其使用寿命,有效解决了该领域中的多项技术难题。展开更多
基金supported by Chinese National Natural Science Foundation (No. 51809016 and No. 51979152)Chongqing Municipal Natural Science Foundation (No. cstc2019jcyjmsxmX0645)
文摘A new blasting approach of combined blastholes with different diameters is proposed to solve the problems of oversize boulders and rock toes in open-pit mine. A non-ideal detonation model and a statistical damage constitutive model are implemented in dynamic finite element analysis to investigate the formation mechanism of oversize boulders and toes. The damage distribution and evolution process of rock blasting fragmentation is simulated, and the scheme is further optimized. Numerical analysis results showed that pocket charges and satellite blastholes can only improve bench top fragmentation, but they cannot reduce the oversize in the middle and bottom of bench as well as the toe problem. The new blasting approach of combined blastholes with different diameters can effectively reduce the oversize boulders and toes as well as the production costs.
文摘This paper presents a novel computational procedure for the maximum dry density of mixed soils containing oversize particles.At first,the large-scale compaction test data for mixed soils are analyzed by an artificial neural network to determine the main factors affecting the compaction.These factors are then imposed on a genetic programming method and a new mathematical equation emerges.The new equation has more conformity with the experimental data in comparison with the previous correction methods.Besides,the mixed soil dry density is associated with most base soil and oversize fraction specifications.With regard to the sensitivity analyses,if the mixed soil contains high percentages of oversize fraction,the mixed soil composition is governed by the specification of oversized grains,such as specific gravity and the maximum grain size and by increasing these factors,the mixed soil dry density is increased.In mixed soil with a low content of oversize,the base soil specification mainly controls the compaction behavior of mixed soil.Furthermore,if the base soil is inherently compacted with greater dry density,adding the oversize slightly improves the mixed soil dry density.In contrast,adding oversized grains to the base soil with a lower dry density produces a mixed soil with greater dry density.By increasing the maximum grain size difference between the oversize fraction and base soil,the dry density of mixed soil is enhanced.
文摘It is an honor to be the vip editor of this special issue on Current Consensus and Controversy on Male Lower Urinary Tract Symptoms(LUTS)/Benign Prostatic Hyperplasia(BPH).As the title implies,one can write on a wide range of topics related to this urological problem that is common worldwide.
基金supported by the National Basic Research Program of China("973"Project)(Grant No.2013CB036204)
文摘Non-cohesive soils have been widely used in construction of high-speed railway for their excellent physical and mechanical properties,and the determination of maximum and minimum dry density of such soils containing oversize particles is an important topic.In this study,the influence of oversize particles on dry density of non-cohesive soils is investigated by packing tests.Test results show that oversize particles will make"extra"voids around their surfaces,which increase significantly if the size ratio of oversize material to matrix material is not very big.The dry density of the total material will be overestimated by Elimination Method due to the omission of the"extra"voids.Thus,a geometric model is proposed by which the"extra"voids can be taken into account,and a new oversize correction method for non-cohesive soils is developed.Test results confirm the applicability of this method on the condition of oversize fraction being less than 40%by mass.
文摘On the evening of May 3,one day before China’s Youth Day,well-known actor He Bing made a speech on Bilibili,a videosharing platform themed around animation and games.The 52-year-old praised the younger generation,especially those born in the 1990s,and expressed his expectations for them.
文摘U.S.Secretary of Commerce Gina Raimondo made a high-profile trip to China last August.There,she talked up the“enormous"Chinese market and the incredible“appetite among U.S.businesses to continue to do business"there.While no significant deals were unveiled during her visit,it did leave the impression that the White House intended to continue open dialogue and continue doing business with China.
文摘From the media,we get the impression that celebrities and public figures recover almost instantly from pregnancy.All of this“news”may leave us questioning what a normal recovery should look and feel like.The reality is it takes months for the body to recuperate from pregnancy:not only to reach pre-pregnancy weight but also to regain pre-pregnancy figure and strength.
文摘对于17-4PH钢超大型锻件而言,其成分宏观偏析、缩孔疏松、碳化物析出、裂纹的产生以及晶粒度的大小通常难以控制,从而严重影响其力学性能和后续的产品使用。以28 t 17-4PH钢电渣锭从生产至获得成品的生产为例,从对重熔渣系设计、锻造工艺流程以及固溶时效热处理等重点工艺入手,优化了产品制造过程,特别通过精确控制固溶和时效工艺,在350~1050℃范围内分步加热保温固溶处理以及150~530℃范围内多次加热保温时效处理,成功控制了产品中残余奥氏体、富铜相及弥散析出相的体积分数,达到了可控的基体晶粒度,有效抑制了不利相的析出,同时显著降低了工件的内部应力及开裂风险。通过优化措施不仅保证了产品的力学性能,而且显著延长了其使用寿命,有效解决了该领域中的多项技术难题。
