Coal bump refers to a sudden catastrophic failure of coal seam and usually can cause serious damages to underground mining facilities and staff. In this circumstance, this paper focuses on the recent achievements in t...Coal bump refers to a sudden catastrophic failure of coal seam and usually can cause serious damages to underground mining facilities and staff. In this circumstance, this paper focuses on the recent achievements in the mechanism and prevention techniques of coal bumps over the past five years in China.Based on theoretical analysis, laboratory experiment, numerical simulation and field test, the characteristics of coal bumps occurrence in China's coal mines were described, and the difference between coal bumps and rockbursts was also discussed. In addition, three categories of coal bumps induced by'material failure' were introduced, i.e. hard roof, floor strata and tectonic structures, in which the mechanism of coal bumps induced by geological structures was analyzed. This involves the bump liability and microstructure effects on bump-prone coal failure, the mechanism of coal bumps in response to fault reactivation, island face mining or hard roof failure. Next, the achievements in the monitoring and controlling methods of coal bumps were reviewed. These methods involve the incorporated prediction system of micro-seismicity and mining-induced pressure, the distributed micro-seismic monitoring system, energy absorption support system, bolts with constant resistance and large elongation,and the 'multi-stage' high-performance support. Finally, an optimal mining design is desirable for the purpose of coal bump mitigation.展开更多
Experiments simulating the effect of coal mine stopping through a fault zone were designed based on a working face of the Qianqiu coal mine in Yima, China. Through simulation of the physical process of fault reactivat...Experiments simulating the effect of coal mine stopping through a fault zone were designed based on a working face of the Qianqiu coal mine in Yima, China. Through simulation of the physical process of fault reactivation and coal bumps, the displacement of the surrounding strata and evolution characteristics of fault stress under the effect of mining were studied. The mechanism of fault reactivation induced by coal mining was analyzed. The results show that shortly before fault reactiva- tion, the normal stress and shear stress increased rapidly and the risk of a fault slip occurring was also increased. The fault reac- tivation, caused by the mining activity, occurred when the working face was 25-35 m from the fault along the hanging wall. The influence of mining increased the possibility of fault reactivation, while the local failure of the bearing capacity of the working face was the direct cause of the fault slip. Our results indicate that the influence of fault slip on the coal of the working face had a transient impact and acted as a loading-unloading function.展开更多
According to the movement and change rules of mechanical structure of surrounding rock coal mass system during coal excavation, the mechanism of sudden instability and damage was found out. The criterions that disting...According to the movement and change rules of mechanical structure of surrounding rock coal mass system during coal excavation, the mechanism of sudden instability and damage was found out. The criterions that distinguishing the occurring of the pressure bump were put forward. This criteria have been applied successfully in the comprehensive prevent of pressure bumps in Tangshan colliery.展开更多
Coal bumps have long been a safety hazard in coal mines, and even after decades of research, the exact mechanics that cause coal bumps are still not well understood. Therefore, coal bumps are still difficult to predic...Coal bumps have long been a safety hazard in coal mines, and even after decades of research, the exact mechanics that cause coal bumps are still not well understood. Therefore, coal bumps are still difficult to predict and control. The LaModel program has a long history of being used to effectively analyze displacements and stresses in coal mines, and with the recent addition of energy release and local mine stiffness calculations, the LaModel program now has greatly increased capabilities for evaluating coal bump potential. This paper presents three recent case histories where coal stress, pillar safety factor, energy release rate and local mine stiffness calculations in LaModel were used to evaluate the pillar plan and cut sequencing that were associated with a number of bumps. The first case history is a longwall mine where a simple stress analysis was used to help determine the limiting depth for safely mining in bump-prone ground. The second case history is a room-and-pillar retreat mine where the LaModel analysis is used to help optimize the pillar extraction sequencing in order to minimize the frequent pillar line bumps. The third case history is the Crandall Canyon mine where an initial bump and then a massive pillar collapse/bump which killed 6 miners is extensively back-analyzed. In these case histories, the calculation tools in LaModel are ultimately shown to be very effective for analyzing various aspects of the bump problem, and in the conclusions, a number of critical insights into the practical calculation of mine failure and stability developed as a result of this research are presented.展开更多
Flow separation due to shock wave/boundary layer interaction is dominated in blade passage with supersonic relative incoming flow,which always accompanies aerodynamic performance penalties.A loss reduction method for ...Flow separation due to shock wave/boundary layer interaction is dominated in blade passage with supersonic relative incoming flow,which always accompanies aerodynamic performance penalties.A loss reduction method for smearing the passage shock foot via Shock Control Bump(SCB)located on transonic compressor rotor blade suction side is implemented to shrink the region of boundary layer separation.The curved windward section of SCB with constant adverse pressure gradient is constructed ahead of passage shock-impingement point at design rotor speed of Rotor 37 to get the improved model.Numerical investigations on both two models have been conducted employing Reynolds-Averaged Navier-Stokes(RANS)method to reveal flow physics of SCB.Comparisons and analyses on simulation results have also been carried out,showing that passage shock foot of baseline is replaced with a family of compression waves and a weaker shock foot for moderate adverse pressure gradient as well as suppression of boundary layer separations and secondary flow of low-momentum fluid within boundary layer.It is found that adiabatic efficiency and total pressure ratio of improved blade exceeds those of baseline at 95%-100%design rotor speed,and then slightly worsens with decrease of rotatory speed till both equal below 60%rated speed.The investigated conclusion implies a potential promise for future practical applications of SCB in both transonic and supersonic compressors.展开更多
Cu bump was transferred using a focused laser pulse for microelectronic packaging.An Nd:YAG laser pulse (maximum energy of 500 mJ;wavelength of 1064 nm;fluences of 0.4-2.1 kJ/cm2) was irradiated on a sacrificial absor...Cu bump was transferred using a focused laser pulse for microelectronic packaging.An Nd:YAG laser pulse (maximum energy of 500 mJ;wavelength of 1064 nm;fluences of 0.4-2.1 kJ/cm2) was irradiated on a sacrificial absorption layer with copper coating.The focused laser beam induced plasma between the semi-transparent donor slide and the sacrificial layer,causing a shock wave.The shock wave pressure pushed the Cu layer and transferred material to deposit a bump on substrate.A beam-shaper was used to produce uniform pressure at the interface to reduce fragmentation of the transferred material on the substrate.The calculated shock wave pressure with respect to laser fluence was 1-3 GPa.A Cu bump of diameter of 200 μm was successfully deposited at laser fluence of 0.6 kJ/cm 2.The pressure control at the sacrificial layer using a laser pulse was critical to produce a bump with less fragmentation.The technique can be applied to forming Cu bump for an interconnecting process in electronics.展开更多
Based on field measurement, the relations was introduced between mining bepth and the peak value places of abutment pressures in long wall face of the deep colliery with caving method to handle goaf, and the reasons a...Based on field measurement, the relations was introduced between mining bepth and the peak value places of abutment pressures in long wall face of the deep colliery with caving method to handle goaf, and the reasons aod kinds of pressure bumps are analysed under the action of tbe moving and constant abutment pressures formed by the method of long wall caving or room and pillar mining, and the relative precautions were put foward to prevent the pressure bumps in deep mining.展开更多
Feature detection in chemical sensors images falls under the general topic of mathematical morphology, where the goal is to detect “image objects” e.g. peaks or spots in an image. Here, we propose a novel method for...Feature detection in chemical sensors images falls under the general topic of mathematical morphology, where the goal is to detect “image objects” e.g. peaks or spots in an image. Here, we propose a novel method for object detection that can be generalized for a k-dimensional object obtained from an analogous higher-dimensional technology source. Our method is based on the smoothing decomposition, Data = Smooth + Rough, where the “rough” (i.e. residual) object from a k-dimensional cross-shaped smoother provides information for object detection. We demonstrate properties of this procedure with chemical sensor applications from various biological fields, including genetic and proteomic data analysis.展开更多
The Explosive Reactive Armors(ERA)are really efficient at reducing Shaped Charge Jet(SCJ)performance.The main destabilizing mechanism is the transverse movement of the front and rear moving plates(MP)on the SCJ.Theref...The Explosive Reactive Armors(ERA)are really efficient at reducing Shaped Charge Jet(SCJ)performance.The main destabilizing mechanism is the transverse movement of the front and rear moving plates(MP)on the SCJ.Therefore,a good understanding of the interaction SCJ/MP is essential for improving both weapon and armor systems.In a previous article,we have shown that interaction regimes are mainly influenced by the local collision geometry.Thus,in the collision point frame,the angle of collision be-tween the continuous SCJ and the MP is a key parameter.This flow angle is acute for the Backward Moving plate(BMP)moving against the SCJ and obtuse for the Forward Moving Plate(FMP)moving alongside it.In the former,the jet is simply deflected,which is the regime 1 of deflection.In the latter,the interaction turns on an alternative creation of fragment and ligament,which is the regime 2.Fragments are parts of the jet that are only slightly deflected while ligaments are the curved material bridges that connect two consecutive fragments.When stretching,the jet is systematically subject to instabilities that disturb its surface,creating necks along it.Their growth finally leads to the jet fragmentation.In this article,we focus on this jet distur-bance and its consequences on the SCJ/MP interaction.An experimental set-up was built to implement the interaction between a SCJ and a moving plate for different collision points,at different stand-off distances.The plate can interact with a smooth SCJ or a disturbed SCJ at a close and a far stand-off distance,respectively.One of the main results is the visualization of a regime change in SCJ/BMP interaction.A regime 1(deflection)interaction changes into a ligament regime interaction(similar to a FMP regime 2)when the collision point stand-off is increased.It is proposed that this change can be attributed as the increase of the amplitude of the jet surface disturbances.This phenomenon is well captured by the gSPH simula-tions.Finally,using both experimental and numerical approaches,we propose a new detailed analysis of the different phenomena occurring during the interaction between a disturbed-surface jet and a moving plate.Interaction regime changes are linked to jet local geometry changes.The interactions of a BMP with a smooth SCJ or with a disturbed surface SCJ are geometrically not the same and,thus,generate different local flows and interaction mechanisms.However,some other simulations have been carried out with constant velocity jet whose surface has been previously disturbed.These simulations underline the influence of both disturbance wavelength l and amplitude A on the interaction regimes.Surface disturbances of the SCJ,linked to its stretching,have a major influence on its interaction with a moving plate.展开更多
This paper describes a technique that can obtain ternary Sn-Ag-In solder bumps with fine pitch and homogenous composition distribution.The main feature of this process is that tin-silver and indium are electroplated o...This paper describes a technique that can obtain ternary Sn-Ag-In solder bumps with fine pitch and homogenous composition distribution.The main feature of this process is that tin-silver and indium are electroplated on copper under bump metallization（UBM） in sequence.After an accurate reflow process,Sn_（1.8）Ag_（9.4）In solder bumps are obtained.It is found that the intermetallic compounds（IMCs） between Sn-Ag-In solder and Cu grow with the reflow time,which results in an increase in Ag concentration in the solder area.So during solidification, more Ag_2In nucleates and strengthens the solder.展开更多
Solder bump technology has been widely used in electronic packaging. With the development of solder bumps towards higher density and finer pitch, it is more difficult to inspect the defects of solder bumps as they are...Solder bump technology has been widely used in electronic packaging. With the development of solder bumps towards higher density and finer pitch, it is more difficult to inspect the defects of solder bumps as they are hidden in the package. A nondestructive method using the transient active thermography has been proposed to inspect the defects of a solder bump, and we aim at developing an intelligent diagnosis system to eliminate the influence of emissivity unevenness and non-uniform heating on defects recognition in active infrared testing. An improved fuzzy c-means(FCM) algorithm based on the entropy weights is investigated in this paper. The captured thermograms are preprocessed to enhance the thermal contrast between the defective and good bumps. Hot spots corresponding to 16 solder bumps are segmented from the thermal images. The statistical features are calculated and selected appropriately to characterize the status of solder bumps in FCM clustering. The missing bump is identified in the FCM result, which is also validated by the principle component analysis. The intelligent diagnosis system using FCM algorithm with the entropy weights is effective for defects recognition in electronic packages.展开更多
基金supported by the National Key Research and Development Program (Grant No. 2016YFC0801401)National Natural Science Foundation of China (Grant No. 41502184)Beijing Natural Science Foundation (Grant No. 2164067)
文摘Coal bump refers to a sudden catastrophic failure of coal seam and usually can cause serious damages to underground mining facilities and staff. In this circumstance, this paper focuses on the recent achievements in the mechanism and prevention techniques of coal bumps over the past five years in China.Based on theoretical analysis, laboratory experiment, numerical simulation and field test, the characteristics of coal bumps occurrence in China's coal mines were described, and the difference between coal bumps and rockbursts was also discussed. In addition, three categories of coal bumps induced by'material failure' were introduced, i.e. hard roof, floor strata and tectonic structures, in which the mechanism of coal bumps induced by geological structures was analyzed. This involves the bump liability and microstructure effects on bump-prone coal failure, the mechanism of coal bumps in response to fault reactivation, island face mining or hard roof failure. Next, the achievements in the monitoring and controlling methods of coal bumps were reviewed. These methods involve the incorporated prediction system of micro-seismicity and mining-induced pressure, the distributed micro-seismic monitoring system, energy absorption support system, bolts with constant resistance and large elongation,and the 'multi-stage' high-performance support. Finally, an optimal mining design is desirable for the purpose of coal bump mitigation.
基金Supported by the Major State Basic Research Development Program Fund （2010CB226801） the National Natural Science Foundation of China （50704034） the State Key Laboratory of Coal Resources and Safe Mining Open Research Fund （SKLCRSM11KFB08）
文摘Experiments simulating the effect of coal mine stopping through a fault zone were designed based on a working face of the Qianqiu coal mine in Yima, China. Through simulation of the physical process of fault reactivation and coal bumps, the displacement of the surrounding strata and evolution characteristics of fault stress under the effect of mining were studied. The mechanism of fault reactivation induced by coal mining was analyzed. The results show that shortly before fault reactiva- tion, the normal stress and shear stress increased rapidly and the risk of a fault slip occurring was also increased. The fault reac- tivation, caused by the mining activity, occurred when the working face was 25-35 m from the fault along the hanging wall. The influence of mining increased the possibility of fault reactivation, while the local failure of the bearing capacity of the working face was the direct cause of the fault slip. Our results indicate that the influence of fault slip on the coal of the working face had a transient impact and acted as a loading-unloading function.
文摘According to the movement and change rules of mechanical structure of surrounding rock coal mass system during coal excavation, the mechanism of sudden instability and damage was found out. The criterions that distinguishing the occurring of the pressure bump were put forward. This criteria have been applied successfully in the comprehensive prevent of pressure bumps in Tangshan colliery.
文摘Coal bumps have long been a safety hazard in coal mines, and even after decades of research, the exact mechanics that cause coal bumps are still not well understood. Therefore, coal bumps are still difficult to predict and control. The LaModel program has a long history of being used to effectively analyze displacements and stresses in coal mines, and with the recent addition of energy release and local mine stiffness calculations, the LaModel program now has greatly increased capabilities for evaluating coal bump potential. This paper presents three recent case histories where coal stress, pillar safety factor, energy release rate and local mine stiffness calculations in LaModel were used to evaluate the pillar plan and cut sequencing that were associated with a number of bumps. The first case history is a longwall mine where a simple stress analysis was used to help determine the limiting depth for safely mining in bump-prone ground. The second case history is a room-and-pillar retreat mine where the LaModel analysis is used to help optimize the pillar extraction sequencing in order to minimize the frequent pillar line bumps. The third case history is the Crandall Canyon mine where an initial bump and then a massive pillar collapse/bump which killed 6 miners is extensively back-analyzed. In these case histories, the calculation tools in LaModel are ultimately shown to be very effective for analyzing various aspects of the bump problem, and in the conclusions, a number of critical insights into the practical calculation of mine failure and stability developed as a result of this research are presented.
基金the funding from the National Key Research and Development Program of China(No.2016YFB0901402)the Key Project of National Natural Science Foundation of China(No.51790513)。
文摘Flow separation due to shock wave/boundary layer interaction is dominated in blade passage with supersonic relative incoming flow,which always accompanies aerodynamic performance penalties.A loss reduction method for smearing the passage shock foot via Shock Control Bump(SCB)located on transonic compressor rotor blade suction side is implemented to shrink the region of boundary layer separation.The curved windward section of SCB with constant adverse pressure gradient is constructed ahead of passage shock-impingement point at design rotor speed of Rotor 37 to get the improved model.Numerical investigations on both two models have been conducted employing Reynolds-Averaged Navier-Stokes(RANS)method to reveal flow physics of SCB.Comparisons and analyses on simulation results have also been carried out,showing that passage shock foot of baseline is replaced with a family of compression waves and a weaker shock foot for moderate adverse pressure gradient as well as suppression of boundary layer separations and secondary flow of low-momentum fluid within boundary layer.It is found that adiabatic efficiency and total pressure ratio of improved blade exceeds those of baseline at 95%-100%design rotor speed,and then slightly worsens with decrease of rotatory speed till both equal below 60%rated speed.The investigated conclusion implies a potential promise for future practical applications of SCB in both transonic and supersonic compressors.
基金Project(2012-0001900)supported by the National Research Foundation of Korea
文摘Cu bump was transferred using a focused laser pulse for microelectronic packaging.An Nd:YAG laser pulse (maximum energy of 500 mJ;wavelength of 1064 nm;fluences of 0.4-2.1 kJ/cm2) was irradiated on a sacrificial absorption layer with copper coating.The focused laser beam induced plasma between the semi-transparent donor slide and the sacrificial layer,causing a shock wave.The shock wave pressure pushed the Cu layer and transferred material to deposit a bump on substrate.A beam-shaper was used to produce uniform pressure at the interface to reduce fragmentation of the transferred material on the substrate.The calculated shock wave pressure with respect to laser fluence was 1-3 GPa.A Cu bump of diameter of 200 μm was successfully deposited at laser fluence of 0.6 kJ/cm 2.The pressure control at the sacrificial layer using a laser pulse was critical to produce a bump with less fragmentation.The technique can be applied to forming Cu bump for an interconnecting process in electronics.
文摘Based on field measurement, the relations was introduced between mining bepth and the peak value places of abutment pressures in long wall face of the deep colliery with caving method to handle goaf, and the reasons aod kinds of pressure bumps are analysed under the action of tbe moving and constant abutment pressures formed by the method of long wall caving or room and pillar mining, and the relative precautions were put foward to prevent the pressure bumps in deep mining.
文摘Feature detection in chemical sensors images falls under the general topic of mathematical morphology, where the goal is to detect “image objects” e.g. peaks or spots in an image. Here, we propose a novel method for object detection that can be generalized for a k-dimensional object obtained from an analogous higher-dimensional technology source. Our method is based on the smoothing decomposition, Data = Smooth + Rough, where the “rough” (i.e. residual) object from a k-dimensional cross-shaped smoother provides information for object detection. We demonstrate properties of this procedure with chemical sensor applications from various biological fields, including genetic and proteomic data analysis.
基金supported by the Ministère des Arméesthe Agence de l'Innovation de Défense (AID)
文摘The Explosive Reactive Armors(ERA)are really efficient at reducing Shaped Charge Jet(SCJ)performance.The main destabilizing mechanism is the transverse movement of the front and rear moving plates(MP)on the SCJ.Therefore,a good understanding of the interaction SCJ/MP is essential for improving both weapon and armor systems.In a previous article,we have shown that interaction regimes are mainly influenced by the local collision geometry.Thus,in the collision point frame,the angle of collision be-tween the continuous SCJ and the MP is a key parameter.This flow angle is acute for the Backward Moving plate(BMP)moving against the SCJ and obtuse for the Forward Moving Plate(FMP)moving alongside it.In the former,the jet is simply deflected,which is the regime 1 of deflection.In the latter,the interaction turns on an alternative creation of fragment and ligament,which is the regime 2.Fragments are parts of the jet that are only slightly deflected while ligaments are the curved material bridges that connect two consecutive fragments.When stretching,the jet is systematically subject to instabilities that disturb its surface,creating necks along it.Their growth finally leads to the jet fragmentation.In this article,we focus on this jet distur-bance and its consequences on the SCJ/MP interaction.An experimental set-up was built to implement the interaction between a SCJ and a moving plate for different collision points,at different stand-off distances.The plate can interact with a smooth SCJ or a disturbed SCJ at a close and a far stand-off distance,respectively.One of the main results is the visualization of a regime change in SCJ/BMP interaction.A regime 1(deflection)interaction changes into a ligament regime interaction(similar to a FMP regime 2)when the collision point stand-off is increased.It is proposed that this change can be attributed as the increase of the amplitude of the jet surface disturbances.This phenomenon is well captured by the gSPH simula-tions.Finally,using both experimental and numerical approaches,we propose a new detailed analysis of the different phenomena occurring during the interaction between a disturbed-surface jet and a moving plate.Interaction regime changes are linked to jet local geometry changes.The interactions of a BMP with a smooth SCJ or with a disturbed surface SCJ are geometrically not the same and,thus,generate different local flows and interaction mechanisms.However,some other simulations have been carried out with constant velocity jet whose surface has been previously disturbed.These simulations underline the influence of both disturbance wavelength l and amplitude A on the interaction regimes.Surface disturbances of the SCJ,linked to its stretching,have a major influence on its interaction with a moving plate.
文摘This paper describes a technique that can obtain ternary Sn-Ag-In solder bumps with fine pitch and homogenous composition distribution.The main feature of this process is that tin-silver and indium are electroplated on copper under bump metallization（UBM） in sequence.After an accurate reflow process,Sn_（1.8）Ag_（9.4）In solder bumps are obtained.It is found that the intermetallic compounds（IMCs） between Sn-Ag-In solder and Cu grow with the reflow time,which results in an increase in Ag concentration in the solder area.So during solidification, more Ag_2In nucleates and strengthens the solder.
基金supported by the National Natural Science Foundation of China(Grant Nos.51305179&51305177)the Natural Science Foundation of Jiangsu Higher Education Institutions(Grant No.13KJB510009)
文摘Solder bump technology has been widely used in electronic packaging. With the development of solder bumps towards higher density and finer pitch, it is more difficult to inspect the defects of solder bumps as they are hidden in the package. A nondestructive method using the transient active thermography has been proposed to inspect the defects of a solder bump, and we aim at developing an intelligent diagnosis system to eliminate the influence of emissivity unevenness and non-uniform heating on defects recognition in active infrared testing. An improved fuzzy c-means(FCM) algorithm based on the entropy weights is investigated in this paper. The captured thermograms are preprocessed to enhance the thermal contrast between the defective and good bumps. Hot spots corresponding to 16 solder bumps are segmented from the thermal images. The statistical features are calculated and selected appropriately to characterize the status of solder bumps in FCM clustering. The missing bump is identified in the FCM result, which is also validated by the principle component analysis. The intelligent diagnosis system using FCM algorithm with the entropy weights is effective for defects recognition in electronic packages.
