When the wing of Oblique Wing Aircraft(OWA) is skewed, the center of gravity, inertia and aerodynamic characteristics of the aircraft all significantly change, causing an undesirable flight dynamic response, affecting...When the wing of Oblique Wing Aircraft(OWA) is skewed, the center of gravity, inertia and aerodynamic characteristics of the aircraft all significantly change, causing an undesirable flight dynamic response, affecting the flying qualities, and even endangering the flight safety. In this study,the dynamic response of an OWA in the wing skewing process is simulated, showing that the threeaxis movements of the OWA are highly coupled and present nonlinear characteristics during the wing skewing. As the roll control efficiency of the aileron decreases due to the shortened control arm in an oblique configuration, the all-moving horizontal tail is used for additional roll and the control allocation is performed based on minimum control energy. Given the properties of pitchroll-yaw coupling and control input and state coupling, and the difficulty of establishing an accurate aerodynamic model in the wing skewing process due to unsteady aerodynamic force, a multi-loop sliding mode controller is formulated by the time-scale separation method. The closed-loop simulation results show that the asymmetric aerodynamics can be balanced and that the velocity and altitude of the aircraft maintain stable, which means that a smooth transition is obtained during the OWA's wing skewing.展开更多
To study the stability of the west slope in Buzhaoba Open-Pit Mine and determine the aging stability coefficient during slide mass development, the deformation band of the west slope and the slide mass structure of th...To study the stability of the west slope in Buzhaoba Open-Pit Mine and determine the aging stability coefficient during slide mass development, the deformation band of the west slope and the slide mass structure of the 34,600 profile are obtained on the basis of hydrology, geology, and monitoring data.The residual thrust method is utilized to calculate the stability coefficients, which are 1.225 and 1.00 under sound and transfixion conditions, respectively. According to the rock damage and fragmentation and the principle of mechanical parameter degradation, the mechanical models of the slide mass development of the hard and soft rock slopes are established. An integrated model for calculating the slope stability coefficient is built considering water, vibration, and other external factors that pertain to the structural plane damage mechanism and the generating mechanism of the sliding mass. The change curve of the stability coefficient in the slide mass development is obtained from the relevant analyses,and afterwards, the stability control measures are proposed. The analysis results indicate that in the cracking stage of the hard rock, the slope stability coefficient decreases linearly with the increase in the length Lbof the hard rock crack zone. The linear slope is positively correlated to rock cohesion c. In the transfixion stage of the soft rock, the decrease speed of the stability coefficient is positively correlated to the residual strength of the soft rock. When the slope is stable, the stability coefficient is in a quadratic-linear relationship with the decreased height Dh of the side slope and in a linear relationship with anchoring force P.展开更多
Steam-assisted combustion elevated flares are currently the most widely used type of petrochemical flares.Due to the complex and variable composition of the waste gas they handle,the combustion environment is severely...Steam-assisted combustion elevated flares are currently the most widely used type of petrochemical flares.Due to the complex and variable composition of the waste gas they handle,the combustion environment is severely affected by meteorological conditions.Key process parameters such as intake composition,flow rate,and real-time data of post-combustion residues are difficult to measure or exhibit lag in data availability.As a result,the control methods for these flares are limited,leading to poor control effectiveness.To address this issue,this paper proposes an adaptive sliding mode control method based on the radial basis function(RBF)network.Firstly,the operational characteristics of the petrochemical flare combustion process are analyzed,and a control model for the combustion process is established based on carbon dioxide detection.Secondly,an RBF neural network-based unknown function approximator is designed to identify the nonlinear part of the actual operating system.Finally,by combining the control model of the petrochemical flare combustion and designing the RBF sliding mode controller with its adaptive control law,fast and stable control of the flare combustion state is achieved.Simulation results demonstrate that the designed control strategy can achieve tracking control of the petrochemical flare combustion state,and the adaptive law also accomplishes system identification.展开更多
The batch dyeing process is a typical nonlinear process with time-delay,where precise controlling of temperature plays a vital role on the dyeing quality.Because the accuracy and robustness of the commonly used propor...The batch dyeing process is a typical nonlinear process with time-delay,where precise controlling of temperature plays a vital role on the dyeing quality.Because the accuracy and robustness of the commonly used proportion integration differentiation(PID) algorithm had been limited,a novel method was developed to precisely control the heating and cooling stages for batch dyeing process based on predictive sliding mode control(SMC) algorithm.Firstly,a special predictive sliding mode model was constructed according to the principle of generalized predictive control(GPC);secondly,an appropriate reference trajectory for SMC was designed based on the improved approaching law;finally,the predictive sliding mode model and the Diophantine equation were used to predict the output and then the optimized control law was derived using the generalized predictive law.This method combined GPC and the SMC with their respective advantages,so it could be applied to time-delay process,making the control system more robust.Simulation experiments show that this algorithm can well track the temperature variation for the batch dyeing process.展开更多
0 INTRODUCTION Submarine slope slides refer to a geological process occurring on submarine slopes or continental margin slopes,where a large amount of sediment or rock layers on the slope lose stability and slide down...0 INTRODUCTION Submarine slope slides refer to a geological process occurring on submarine slopes or continental margin slopes,where a large amount of sediment or rock layers on the slope lose stability and slide downward along the sliding surface(Kamran et al.,2023;Tong et al.,2023;Hampton et al.,1996).展开更多
As a key assembly in the 5-axis CNC machine tools, positioning precision of the A-axis directly affects the machining accuracy and surface quality of the parts. First of all, mechanical structure and control system of...As a key assembly in the 5-axis CNC machine tools, positioning precision of the A-axis directly affects the machining accuracy and surface quality of the parts. First of all, mechanical structure and control system of the A-axis are designed. Then, considering the influence of nonlin- ear friction, backlash, unmodeled dynamics, uncertain cutting force and other external disturbance on the control precision of the A-axis, an adaptive sliding mode control （ASMC） based on extended state observer （ESO） is proposed. ESO is employed to estimate the state variables of the unknown system and an adaptive law is adopted to compensate for the input dead-zone caused by friction, backlash and other nonlinear characteristics. Finally, stability of the closed-loop system is guaran- teed by the Lyapunov theory. Positioning experiments illustrate the perfect estimation of ESO and the stronger anti-interference and robustness of ASMC, which can improve the control precision of the A-axis by about 40 times. Processing experiments show that the ASMC can reduce the waviness, averaKe error and roughness of the nrocessed surface by 35.63%, 31.31% and 30.35%, respectively.展开更多
Affected by typhoons over years, Fujian Province in Southeast China has developed a large number of shallow landslides, causing a long-term concern for the local government. The study on shallow landslide is not only ...Affected by typhoons over years, Fujian Province in Southeast China has developed a large number of shallow landslides, causing a long-term concern for the local government. The study on shallow landslide is not only helpful to the local government in disaster prevention, but also the theoretical basis of regional early warning technology. To determine the whole-process characteristics and failure mechanisms of flow-slide failure of granite residual soil slopes, we conducted a detailed hazard investigation in Minqing County, Fujian Province, which was impacted by Typhoon Lupit-induced heavy rainfall in August 2021. Based on the investigation and preliminary analysis results, we conducted indoor artificial rainfall physical model tests and obtained the whole-process characteristics of flow-slide failure of granite residual soil landslides. Under the action of heavy rainfall, a granite residual soil slope experiences initial deformation at the slope toe and exhibits development characteristics of continuous traction deformation toward the middle and upper parts of the slope. The critical volumetric water content during slope failure is approximately 53%. Granite residual soil is in a state of high volumetric water content under heavy rainfall conditions, and the shear strength decreases, resulting in a decrease in stability and finally failure occurrence. The new free face generated after failure constitutes an adverse condition for continued traction deformation and failure. As the soil permeability(cm/h) is less than the rainfall intensity(mm/h), and it is difficult for rainwater to continuously infiltrate in short-term rainfall, the influence depth of heavy rainfall is limited. The load of loose deposits at the slope foot also limits the development of deep deformation and failure. With the continuous effect of heavy rainfall, the surface runoff increases gradually, and the influence mode changes from instability failure caused by rainfall infiltration to erosion and scouring of surface runoff on slope surface. Transportation of loose materials by surface runoff is an important reason for prominent siltation in disaster-prone areas.展开更多
Sliding gate control system is widely employed in continuous casting process of steel to control flow rate of molten steel.As molten steel passes through a sliding gate,uneven flow develops.This will cause asymmetrica...Sliding gate control system is widely employed in continuous casting process of steel to control flow rate of molten steel.As molten steel passes through a sliding gate,uneven flow develops.This will cause asymmetrical distribution of flow and temperature field in mold consequently,formation of vortex near the nozzle and entrapment of CC powder into the molten steel.etc,which have negative effect on process productivity and product quality.To suppress the uneven flow,electromagnetic swirling flow has been proposed to impose on the flow in submerged entry nozzle below the sliding gate.In this study the uneven flow developed by incompletely open sliding gate and the suppression of this uneven flow using electromagnetic swirling flow are numerically studied in round billet continuous casting of steel process.The improvement of the flow and temperature filed in the submerged entry nozzle and mold are investigated.It is found that:The uneven velocity in nozzle can be suppressed by electromagnetic swirling flow,and the flow and temperature field in mold be improved obviously;With the increase of electromagnetic swirling intensity,the effect of uneven flow can be almost completely suppressed.展开更多
The coarse-grained WE54 magnesium alloy was heat treated in order to have minimum hardness minimizing the effects of precipitates and solid solution. Friction stir processing(FSP) was applied in severe conditions to o...The coarse-grained WE54 magnesium alloy was heat treated in order to have minimum hardness minimizing the effects of precipitates and solid solution. Friction stir processing(FSP) was applied in severe conditions to obtain fine, equiaxed and highly misoriented grains, with grain sizes even less than 1 μm. The high severity of processing demonstrated to have a strong impact in the microstructure. Consequently,the processed materials exhibited excellent superplasticity at the high strain rate 10^(-2)s^(-1), and temperatures between 300 and 400 ℃. The maximum tensile superplastic elongation of 756% was achieved at 400 ℃ thanks to the operation of grain boundary sliding mechanism(GBS). Besides the new data obtained through tensile testing, the paper deals with a transcendental question regarding the large differences in strain rate values at a given stress in the superplastic regime at maximum elongation compared to other magnesium-based alloys. With this is mind, 19 magnesium alloys from 22 different investigations were analyzed to give some light to this behavior that never was treated before. It is proposed that this behavior has to be attributed to the accommodation process, necessary for GBS to occur, which is hindered by reinforcing solutes.展开更多
Iron alloyed Ni3Al with composition of Ni-18. 8Ab10. 7Fe-0. 5Mn-0. 5Ti-0. 2B in atom percent （NAC alloy） showed attractive tribological properties under unlubrication condition at room temperature. The alloy was pre...Iron alloyed Ni3Al with composition of Ni-18. 8Ab10. 7Fe-0. 5Mn-0. 5Ti-0. 2B in atom percent （NAC alloy） showed attractive tribological properties under unlubrication condition at room temperature. The alloy was prepared by hot isostatic pressing （HIP） process. The wear properties were associated with its intrinsic deformation mechanism. Unfortunately, the single phase NAC-alloy worked inadequately with its counterpart disk, and also showed a poor machinability. In the present work, NAC-alloy matrix composite with 6 % （volume percent） MnS particle addi- tion was studied to improve its wear behaviors and performance on machining. Two metallurgical processes of HIP and vacuum casting were applied to produce the testing materials. Pin-on-disk （POD） measurements were carried out at room temperature. A commercial vermicular graphite cast iron was selected as a reference material. The counter- part disk was made of a grey cast iron as liner material in ship engines. The contact pressures of 2.83 MPa and 5.66 MPa were normally applied in the tests. The investigation indicated that MnS particle addition in the NAC-alloy composites functions as an effective solid lubricant, and improved wear properties and machinability of the materials. Obvi- ously, as-cast NAC-alloy with in-situ formed MnS-phase was working more effectively with the counterpart, compa- ring to the HIPed NAC-alloy composite with MnS particles. At the high contact pressure of 5.66 MPa, the specific wear rate of the as-cast NAC-alloy composite was high. The phenomenon of the negative effect is mostly due to the brittle second NiAl phase as evidenced in the microstructure analysis.展开更多
Tangjiashan landslide is a typical high-speed landslide hosted on consequent bedding rock. The landslide was induced by Wenchuan earthquake at a medium-steep hill slope. The occurrence of Tangjiashan landslide was bas...Tangjiashan landslide is a typical high-speed landslide hosted on consequent bedding rock. The landslide was induced by Wenchuan earthquake at a medium-steep hill slope. The occurrence of Tangjiashan landslide was basically controlled by the tectonic structure, topography, stratum lithology, slope structure, seismic waves, and strike of river. Among various factors, the seismic loading with great intensity and long duration was dominant. The landslide initiation exhibited the local amplification effect of seismic waves at the rear of the slope, the dislocation effect on the fault, and the shear failure differentiating effect on the regions between the soft and the hard layers. Based on field investigations and with the employment of the distinct element numerical simulation program UDEC （universal distinct element code）, the whole kinetic sliding process of Tan iashan landslide was represented and the formation mechanism of the consequent rock landslide under seismic loading was studied. The results are helpful for understanding seismic dynamic responses of consequent bedding rock slopes, where the slope stability could be governed by earthquakes.展开更多
A high-performance, distributed, complex-event processing en- gine with improved scalability is proposed. In this new engine, the stateless proeessing node is combined with distributed stor- age so that scale and perf...A high-performance, distributed, complex-event processing en- gine with improved scalability is proposed. In this new engine, the stateless proeessing node is combined with distributed stor- age so that scale and performance can be linearly expanded. This design prevents single node failure and makes the system highly reliable.展开更多
A defining characteristic of continuous queries over on-line data streams,possibly bounded by sliding windows,is the potentially infinite and time-evolving nature of their inputs and outputs.For different update patte...A defining characteristic of continuous queries over on-line data streams,possibly bounded by sliding windows,is the potentially infinite and time-evolving nature of their inputs and outputs.For different update patterns of continuous queries,suitable data structures bring great query processing efficiency.In this paper,we proposed a data structure suitable for weak nonmonotonic update pattern in which the lifetime of each tuple is known at generation time,but the length of lifetime is not necessarily the same.The new data structure combined the ladder queue with the feature of weak non-monotonic update pattern.The experiment results show that the new data structure performs much better than the traditional calendar queue in many cases.展开更多
基金supported by the National Natural Science Foundation of China (No. 11402010)
文摘When the wing of Oblique Wing Aircraft(OWA) is skewed, the center of gravity, inertia and aerodynamic characteristics of the aircraft all significantly change, causing an undesirable flight dynamic response, affecting the flying qualities, and even endangering the flight safety. In this study,the dynamic response of an OWA in the wing skewing process is simulated, showing that the threeaxis movements of the OWA are highly coupled and present nonlinear characteristics during the wing skewing. As the roll control efficiency of the aileron decreases due to the shortened control arm in an oblique configuration, the all-moving horizontal tail is used for additional roll and the control allocation is performed based on minimum control energy. Given the properties of pitchroll-yaw coupling and control input and state coupling, and the difficulty of establishing an accurate aerodynamic model in the wing skewing process due to unsteady aerodynamic force, a multi-loop sliding mode controller is formulated by the time-scale separation method. The closed-loop simulation results show that the asymmetric aerodynamics can be balanced and that the velocity and altitude of the aircraft maintain stable, which means that a smooth transition is obtained during the OWA's wing skewing.
基金financially supported by the National Natural Science Foundation of China (No. 51034005)National High Technology Research and Development Program of China (No. 2012AA062004)Program for New Century Excellent Talents in University of China (No. NCET-13-1022)
文摘To study the stability of the west slope in Buzhaoba Open-Pit Mine and determine the aging stability coefficient during slide mass development, the deformation band of the west slope and the slide mass structure of the 34,600 profile are obtained on the basis of hydrology, geology, and monitoring data.The residual thrust method is utilized to calculate the stability coefficients, which are 1.225 and 1.00 under sound and transfixion conditions, respectively. According to the rock damage and fragmentation and the principle of mechanical parameter degradation, the mechanical models of the slide mass development of the hard and soft rock slopes are established. An integrated model for calculating the slope stability coefficient is built considering water, vibration, and other external factors that pertain to the structural plane damage mechanism and the generating mechanism of the sliding mass. The change curve of the stability coefficient in the slide mass development is obtained from the relevant analyses,and afterwards, the stability control measures are proposed. The analysis results indicate that in the cracking stage of the hard rock, the slope stability coefficient decreases linearly with the increase in the length Lbof the hard rock crack zone. The linear slope is positively correlated to rock cohesion c. In the transfixion stage of the soft rock, the decrease speed of the stability coefficient is positively correlated to the residual strength of the soft rock. When the slope is stable, the stability coefficient is in a quadratic-linear relationship with the decreased height Dh of the side slope and in a linear relationship with anchoring force P.
基金gratefully acknowledge the financial support from the Scientific and Technological Innovation 2030-“New Generation Artificial Intelligence”Major Project(2021ZD0112301)National Natural Science Foundation of China(62273011,62076013,62303027).
文摘Steam-assisted combustion elevated flares are currently the most widely used type of petrochemical flares.Due to the complex and variable composition of the waste gas they handle,the combustion environment is severely affected by meteorological conditions.Key process parameters such as intake composition,flow rate,and real-time data of post-combustion residues are difficult to measure or exhibit lag in data availability.As a result,the control methods for these flares are limited,leading to poor control effectiveness.To address this issue,this paper proposes an adaptive sliding mode control method based on the radial basis function(RBF)network.Firstly,the operational characteristics of the petrochemical flare combustion process are analyzed,and a control model for the combustion process is established based on carbon dioxide detection.Secondly,an RBF neural network-based unknown function approximator is designed to identify the nonlinear part of the actual operating system.Finally,by combining the control model of the petrochemical flare combustion and designing the RBF sliding mode controller with its adaptive control law,fast and stable control of the flare combustion state is achieved.Simulation results demonstrate that the designed control strategy can achieve tracking control of the petrochemical flare combustion state,and the adaptive law also accomplishes system identification.
基金National Natural Science Foundation of China(No.61074154)
文摘The batch dyeing process is a typical nonlinear process with time-delay,where precise controlling of temperature plays a vital role on the dyeing quality.Because the accuracy and robustness of the commonly used proportion integration differentiation(PID) algorithm had been limited,a novel method was developed to precisely control the heating and cooling stages for batch dyeing process based on predictive sliding mode control(SMC) algorithm.Firstly,a special predictive sliding mode model was constructed according to the principle of generalized predictive control(GPC);secondly,an appropriate reference trajectory for SMC was designed based on the improved approaching law;finally,the predictive sliding mode model and the Diophantine equation were used to predict the output and then the optimized control law was derived using the generalized predictive law.This method combined GPC and the SMC with their respective advantages,so it could be applied to time-delay process,making the control system more robust.Simulation experiments show that this algorithm can well track the temperature variation for the batch dyeing process.
基金supported by the National Natural Science Foundation of China(Nos.42090054,42377192)the Scientific Research Project of Power China Huadong Engineering Corporation Limited(No.KY2022-KC-02-02)the Natural Science Foundation of Hubei Province,China(No.2022CFA002)。
文摘0 INTRODUCTION Submarine slope slides refer to a geological process occurring on submarine slopes or continental margin slopes,where a large amount of sediment or rock layers on the slope lose stability and slide downward along the sliding surface(Kamran et al.,2023;Tong et al.,2023;Hampton et al.,1996).
基金supported by National Science and Technology Major Project of the Ministry of Science and Technology of China (No. 2013ZX04001081)
文摘As a key assembly in the 5-axis CNC machine tools, positioning precision of the A-axis directly affects the machining accuracy and surface quality of the parts. First of all, mechanical structure and control system of the A-axis are designed. Then, considering the influence of nonlin- ear friction, backlash, unmodeled dynamics, uncertain cutting force and other external disturbance on the control precision of the A-axis, an adaptive sliding mode control （ASMC） based on extended state observer （ESO） is proposed. ESO is employed to estimate the state variables of the unknown system and an adaptive law is adopted to compensate for the input dead-zone caused by friction, backlash and other nonlinear characteristics. Finally, stability of the closed-loop system is guaran- teed by the Lyapunov theory. Positioning experiments illustrate the perfect estimation of ESO and the stronger anti-interference and robustness of ASMC, which can improve the control precision of the A-axis by about 40 times. Processing experiments show that the ASMC can reduce the waviness, averaKe error and roughness of the nrocessed surface by 35.63%, 31.31% and 30.35%, respectively.
基金funded by the National Natural Science Foundation of China(Grant Nos.U2005205,41977252)National Key R&D Program of China(2018YFC1505503)+1 种基金Open Fund of Key Laboratory of Geohazard Prevention of Hilly Mountains,Ministry of Natural Resources(Fujian Key Laboratory of Geohazard Prevention)(FJKLGH2022K001)the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project(Grant No.SKLGP2020Z001)。
文摘Affected by typhoons over years, Fujian Province in Southeast China has developed a large number of shallow landslides, causing a long-term concern for the local government. The study on shallow landslide is not only helpful to the local government in disaster prevention, but also the theoretical basis of regional early warning technology. To determine the whole-process characteristics and failure mechanisms of flow-slide failure of granite residual soil slopes, we conducted a detailed hazard investigation in Minqing County, Fujian Province, which was impacted by Typhoon Lupit-induced heavy rainfall in August 2021. Based on the investigation and preliminary analysis results, we conducted indoor artificial rainfall physical model tests and obtained the whole-process characteristics of flow-slide failure of granite residual soil landslides. Under the action of heavy rainfall, a granite residual soil slope experiences initial deformation at the slope toe and exhibits development characteristics of continuous traction deformation toward the middle and upper parts of the slope. The critical volumetric water content during slope failure is approximately 53%. Granite residual soil is in a state of high volumetric water content under heavy rainfall conditions, and the shear strength decreases, resulting in a decrease in stability and finally failure occurrence. The new free face generated after failure constitutes an adverse condition for continued traction deformation and failure. As the soil permeability(cm/h) is less than the rainfall intensity(mm/h), and it is difficult for rainwater to continuously infiltrate in short-term rainfall, the influence depth of heavy rainfall is limited. The load of loose deposits at the slope foot also limits the development of deep deformation and failure. With the continuous effect of heavy rainfall, the surface runoff increases gradually, and the influence mode changes from instability failure caused by rainfall infiltration to erosion and scouring of surface runoff on slope surface. Transportation of loose materials by surface runoff is an important reason for prominent siltation in disaster-prone areas.
基金Item Sponsored by The Central Universities(N100409010)Project for Key Laboratory of Liaoning Province(LS2010065)"111 project" of Northeastern University,China(B07015)
文摘Sliding gate control system is widely employed in continuous casting process of steel to control flow rate of molten steel.As molten steel passes through a sliding gate,uneven flow develops.This will cause asymmetrical distribution of flow and temperature field in mold consequently,formation of vortex near the nozzle and entrapment of CC powder into the molten steel.etc,which have negative effect on process productivity and product quality.To suppress the uneven flow,electromagnetic swirling flow has been proposed to impose on the flow in submerged entry nozzle below the sliding gate.In this study the uneven flow developed by incompletely open sliding gate and the suppression of this uneven flow using electromagnetic swirling flow are numerically studied in round billet continuous casting of steel process.The improvement of the flow and temperature filed in the submerged entry nozzle and mold are investigated.It is found that:The uneven velocity in nozzle can be suppressed by electromagnetic swirling flow,and the flow and temperature field in mold be improved obviously;With the increase of electromagnetic swirling intensity,the effect of uneven flow can be almost completely suppressed.
基金Financial support from MINECO (Spain), Project MAT2015–68919-C3–1-R (MINECO/FEDER)CENIM, CSIC, for a contract funded by the aforementioned projectMINECO for a FPI fellowship, number BES2013–063963 (MINECO/FEDER/ESF)。
文摘The coarse-grained WE54 magnesium alloy was heat treated in order to have minimum hardness minimizing the effects of precipitates and solid solution. Friction stir processing(FSP) was applied in severe conditions to obtain fine, equiaxed and highly misoriented grains, with grain sizes even less than 1 μm. The high severity of processing demonstrated to have a strong impact in the microstructure. Consequently,the processed materials exhibited excellent superplasticity at the high strain rate 10^(-2)s^(-1), and temperatures between 300 and 400 ℃. The maximum tensile superplastic elongation of 756% was achieved at 400 ℃ thanks to the operation of grain boundary sliding mechanism(GBS). Besides the new data obtained through tensile testing, the paper deals with a transcendental question regarding the large differences in strain rate values at a given stress in the superplastic regime at maximum elongation compared to other magnesium-based alloys. With this is mind, 19 magnesium alloys from 22 different investigations were analyzed to give some light to this behavior that never was treated before. It is proposed that this behavior has to be attributed to the accommodation process, necessary for GBS to occur, which is hindered by reinforcing solutes.
基金Item Sponsored by Swedish VINNOVA and Chinese MOST for International Colla borative Research Projects(P32737-1,P32737-2)
文摘Iron alloyed Ni3Al with composition of Ni-18. 8Ab10. 7Fe-0. 5Mn-0. 5Ti-0. 2B in atom percent （NAC alloy） showed attractive tribological properties under unlubrication condition at room temperature. The alloy was prepared by hot isostatic pressing （HIP） process. The wear properties were associated with its intrinsic deformation mechanism. Unfortunately, the single phase NAC-alloy worked inadequately with its counterpart disk, and also showed a poor machinability. In the present work, NAC-alloy matrix composite with 6 % （volume percent） MnS particle addi- tion was studied to improve its wear behaviors and performance on machining. Two metallurgical processes of HIP and vacuum casting were applied to produce the testing materials. Pin-on-disk （POD） measurements were carried out at room temperature. A commercial vermicular graphite cast iron was selected as a reference material. The counter- part disk was made of a grey cast iron as liner material in ship engines. The contact pressures of 2.83 MPa and 5.66 MPa were normally applied in the tests. The investigation indicated that MnS particle addition in the NAC-alloy composites functions as an effective solid lubricant, and improved wear properties and machinability of the materials. Obvi- ously, as-cast NAC-alloy with in-situ formed MnS-phase was working more effectively with the counterpart, compa- ring to the HIPed NAC-alloy composite with MnS particles. At the high contact pressure of 5.66 MPa, the specific wear rate of the as-cast NAC-alloy composite was high. The phenomenon of the negative effect is mostly due to the brittle second NiAl phase as evidenced in the microstructure analysis.
基金Supported by the National Natural Science Foundation of China (40772175,40972175)the Scientific Research Fund of Southwest Jiaotong University(2008-A01)+1 种基金the Doctoral Student Innovation Fund of Southwest Jiaotong Universitythe National Natural Science Foundation of China-Yunan Joint Fund (U1033601)
文摘Tangjiashan landslide is a typical high-speed landslide hosted on consequent bedding rock. The landslide was induced by Wenchuan earthquake at a medium-steep hill slope. The occurrence of Tangjiashan landslide was basically controlled by the tectonic structure, topography, stratum lithology, slope structure, seismic waves, and strike of river. Among various factors, the seismic loading with great intensity and long duration was dominant. The landslide initiation exhibited the local amplification effect of seismic waves at the rear of the slope, the dislocation effect on the fault, and the shear failure differentiating effect on the regions between the soft and the hard layers. Based on field investigations and with the employment of the distinct element numerical simulation program UDEC （universal distinct element code）, the whole kinetic sliding process of Tan iashan landslide was represented and the formation mechanism of the consequent rock landslide under seismic loading was studied. The results are helpful for understanding seismic dynamic responses of consequent bedding rock slopes, where the slope stability could be governed by earthquakes.
文摘A high-performance, distributed, complex-event processing en- gine with improved scalability is proposed. In this new engine, the stateless proeessing node is combined with distributed stor- age so that scale and performance can be linearly expanded. This design prevents single node failure and makes the system highly reliable.
基金Funded by the Natural Science Foundation of China (No. 60873030)National High Technology Research and Development Program of China (No. 2007AA01Z309)Defense Pre-Research Foundation of China (No. 9140A04010209JW0504 and No. 9140A15040208JW0501)
文摘A defining characteristic of continuous queries over on-line data streams,possibly bounded by sliding windows,is the potentially infinite and time-evolving nature of their inputs and outputs.For different update patterns of continuous queries,suitable data structures bring great query processing efficiency.In this paper,we proposed a data structure suitable for weak nonmonotonic update pattern in which the lifetime of each tuple is known at generation time,but the length of lifetime is not necessarily the same.The new data structure combined the ladder queue with the feature of weak non-monotonic update pattern.The experiment results show that the new data structure performs much better than the traditional calendar queue in many cases.
