The exploration of Mars would heavily rely on Martian rocks mechanics and engineering technology.As the mechanical property of Martian rocks is uncertain,it is of utmost importance to predict the probability distribut...The exploration of Mars would heavily rely on Martian rocks mechanics and engineering technology.As the mechanical property of Martian rocks is uncertain,it is of utmost importance to predict the probability distribution of Martian rocks mechanical property for the success of Mars exploration.In this paper,a fast and accurate probability distribution method for predicting the macroscale elastic modulus of Martian rocks was proposed by integrating the microscale rock mechanical experiments(micro-RME),accurate grain-based modeling(AGBM)and upscaling methods based on reliability principles.Firstly,the microstructure of NWA12564 Martian sample and elastic modulus of each mineral were obtained by micro-RME with TESCAN integrated mineral analyzer(TIMA)and nanoindentation.The best probability distribution function of the minerals was determined by Kolmogorov-Smirnov(K-S)test.Secondly,based on best distribution function of each mineral,the Monte Carlo simulations(MCS)and upscaling methods were implemented to obtain the probability distribution of upscaled elastic modulus.Thirdly,the correlation between the upscaled elastic modulus and macroscale elastic modulus obtained by AGBM was established.The accurate probability distribution of the macroscale elastic modulus was obtained by this correlation relationship.The proposed method can predict the probability distribution of Martian rocks mechanical property with any size and shape samples.展开更多
Grain size effect on rock strength is a topic of great interest in geotechnical engineering.A consensus obtained from earlier laboratory tests is that rock strength generally decreases with the increase of grain size ...Grain size effect on rock strength is a topic of great interest in geotechnical engineering.A consensus obtained from earlier laboratory tests is that rock strength generally decreases with the increase of grain size for both silicate and carbonate rocks;however,some recent numerical results conflict with such laboratory test results.To address this intriguing issue,the effect of grain size on strength of polymineralic crystalline rock with low porosity is investigated numerically using the grain-based modeling(GBM)approach in discrete element method(DEM)by interpreting micro-cracking process in response to loading.In agreement with some previous DEM simulation results,the simulated rock strength is found to increase with increasing grain size for both homogeneous and heterogeneous models,even when the number of assembled disks in one mineral grain changes.The mechanism of strength increase with increasing grain size is mainly associated with the number of assembled smooth-joint contacts along grain interfaces and the generation of grain boundary cracks in response to loading.The grain interfaces significantly weaken the integrity of the rock model,which is similar to effects of inherent defects in real rock.As the grain size increases,fewer grain interfaces are built in the model and the rock strength becomes much higher.Hence,by solely changing the mineral grain size in a model,the mechanism of grain size effect as observed in laboratory tests cannot be replicated.To address this issue,a method of degradation of grain boundary strength parameters is used to mimic the possible mechanism of grain size effect.The simulated strength using the method becomes comparable with those obtained from laboratory tests when the heterogeneity in the rock is considered.Degradation of grain boundary parameters with increasing grain size provides a plausible explanation for the grain size effect on rock strength.展开更多
With the continuous upgrading of traditional manufacturing industries and the rapid rise of emerging technology fields,the performance requirements for the permanent magnet synchronous motors(PMSMs)have become higher ...With the continuous upgrading of traditional manufacturing industries and the rapid rise of emerging technology fields,the performance requirements for the permanent magnet synchronous motors(PMSMs)have become higher and higher.The importance of fast and accurate electromagnetic thermal coupling analysis of such motors becomes more and more prominent.In view of this,the surfacemounted PMSM(SPMSM)equipped with unequally thick magnetic poles is taken as the main object and its electromagnetic thermal coupling analytical model(ETc AM)is investigated.First,the electromagnetic analytical model(EAM)is studied based on the modified subdomain method.It realizes the fast calculation of key electromagnetic characteristics.Subsequently,the 3D thermal analytical model(TAM)is developed by combining the EAM,the lumped parameter thermal network method(LPTNM),and the partial differential equation of heat flux.It realizes the fast calculation of key thermal characteristics in 3D space.Further,the information transfer channel between EAM and TAM is built with reference to the intrinsic connection between electromagnetic field and temperature field.Thereby,the novel ETcAM is proposed to realize the fast and accurate prediction of electromagnetic and temperature fields.Besides,ETcAM has a lot to commend it.One is that it well accounts for the complex structure,saturation,and heat exchange behavior.Second,it saves a lot of computer resources.It offers boundless possibilities for initial design,scheme evaluation,and optimization of motors.Finally,the validity,accuracy,and practicality of this study are verified by simulation and experiment.展开更多
Oxidative stress has been associated with a number of physiological problems in swine,including reduced production efficiency.Recently,although there has been increased research into regulatory mechanisms and antioxid...Oxidative stress has been associated with a number of physiological problems in swine,including reduced production efficiency.Recently,although there has been increased research into regulatory mechanisms and antioxidant strategies in relation to oxidative stress-induced pig production,it remains so far largely unsuccessful to develop accurate models and nutritional strategies for specific oxidative stress factors.Here,we discuss the dose and dose intensity of the causes of oxidative stress involving physiological,environmental and dietary factors,recent research models and the antioxidant strategies to provide theoretical guidance for future oxidative stress research in swine.展开更多
A grain-based distinct element model featuring three-dimensional （3D） Voronoi tessellations （randompoly-crystals） is proposed for simulation of crack damage development in brittle rocks. The grainboundaries in pol...A grain-based distinct element model featuring three-dimensional （3D） Voronoi tessellations （randompoly-crystals） is proposed for simulation of crack damage development in brittle rocks. The grainboundaries in poly-crystal structure produced by Voronoi tessellations can represent flaws in intact rockand allow for numerical replication of crack damage progression through initiation and propagation ofmicro-fractures along grain boundaries. The Voronoi modelling scheme has been used widely in the pastfor brittle fracture simulation of rock materials. However the difficulty of generating 3D Voronoi modelshas limited its application to two-dimensional （2D） codes. The proposed approach is implemented inNeper, an open-source engine for generation of 3D Voronoi grains, to generate block geometry files thatcan be read directly into 3DEC. A series of Unconfined Compressive Strength （UCS） tests are simulated in3DEC to verify the proposed methodology for 3D simulation of brittle fractures and to investigate therelationship between each micro-parameter and the model＇s macro-response. The possibility of numericalreplication of the classical U-shape strength curve for anisotropic rocks is also investigated innumerical UCS tests by using complex-shaped （elongated） grains that are cemented to one another alongtheir adjoining sides. A micro-parameter calibration procedure is established for 3D Voronoi models foraccurate replication of the mechanical behaviour of isotropic and anisotropic （containing a fabric） rocks. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.展开更多
The objective of this paper is to develop a methodology for calibration of a discrete element grain-based model(GBM)to replicate the hydro-mechanical properties of a brittle rock measured in the laboratory,and to appl...The objective of this paper is to develop a methodology for calibration of a discrete element grain-based model(GBM)to replicate the hydro-mechanical properties of a brittle rock measured in the laboratory,and to apply the calibrated model to simulating the formation of excavation damage zone(EDZ)around underground excavations.Firstly,a new cohesive crack model is implemented into the universal distinct element code(UDEC)to control the fracturing behaviour of materials under various loading modes.Next,a methodology for calibration of the components of the UDEC-Voronoi model is discussed.The role of connectivity of induced microcracks on increasing the permeability of laboratory-scale samples is investigated.The calibrated samples are used to investigate the influence of pore fluid pressure on weakening the drained strength of the laboratory-scale rock.The validity of the Terzaghi’s effective stress law for the drained peak strength of low-porosity rock is tested by performing a series of biaxial compression test simulations.Finally,the evolution of damage and pore pressure around two unsupported circular tunnels in crystalline granitic rock is studied.展开更多
:A new accurate algorithms based on mathematical modeling of two parallel transmissions lines system(TPTLS)as influenced by the mutual effect to determine the fault location is discussed in this work.The distance rela...:A new accurate algorithms based on mathematical modeling of two parallel transmissions lines system(TPTLS)as influenced by the mutual effect to determine the fault location is discussed in this work.The distance relay measures the impedance to the fault location which is the positive-sequence.The principle of summation the positive-,negative-,and zero-sequence voltages which equal zero is used to determine the fault location on the TPTLS.Also,the impedance of the transmission line to the fault location is determined.These algorithms are applied to single-line-to-ground(SLG)and double-line-to-ground(DLG)faults.To detect the fault location along the transmission line,its impedance as seen by the distance relay is determined to indicate if the fault is within the relay’s reach area.TPTLS under study are fed from one-and both-ends.A schematic diagrams are obtained for the impedance relays to determine the fault location with high accuracy.展开更多
Viscosity of natural gas is a basic and important parameter,of theoretical and practical significance in the domain of natural gas recovery,transmission and processing.In order to obtain the accurate viscosity data ef...Viscosity of natural gas is a basic and important parameter,of theoretical and practical significance in the domain of natural gas recovery,transmission and processing.In order to obtain the accurate viscosity data efficiently at a low cost,a new model and its corresponding functional relation are derived on the basis of the relationship among viscosity,temperature and density derived from the kinetic theory of gases.After the model parameters were optimized using a lot of experimental data,the diagram showing the variation of viscosity along with temperature and density is prepared,showing that:①the gas viscosity increases with the increase of density as well as the increase of temperature in the low density region;②the gas viscosity increases with the decrease of temperature in high density region.With this new model,the viscosity of 9 natural gas samples was calculated precisely.The average relative deviation between these calculated values and 1539 experimental data measured at 250e450 K and 0.10e140.0 MPa is less than 1.9%.Compared with the 793 experimental data with a measurement error less than 0.5%,the maximum relative deviation is less than 0.98%.It is concluded that this new model is more advantageous than the previous 8 models in terms of simplicity,accuracy,fast calculation,and direct applicability to the CO_(2) bearing gas samples.展开更多
A novel accurate tracking controller is developed for the longitudinal dynamics of Hypersonic Flight Vehicles(HFVs)in the presence of large model uncertainties,external disturbances and actuator nonlinearities.Distinc...A novel accurate tracking controller is developed for the longitudinal dynamics of Hypersonic Flight Vehicles(HFVs)in the presence of large model uncertainties,external disturbances and actuator nonlinearities.Distinct from the state-of-the-art,besides being continuity,no restrictive conditions have been imposed on the HFVs dynamics.The system uncertainties are skillfully handled by being seen as bounded"disturbance terms".In addition,by means of backstepping adaptive technique,the accurate tracking(i.e.tracking errors converge to zero as time approaches infinity)rather than bounded tracking(i.e.tracking errors converge to residual sets)has been achieved.What’s more,the accurate tracking problems for HFVs subject to actuator dead-zone and hysteresis are discussed,respectively.Then,all signals of closed-loop system are verified to be Semi-Global Uniformly Ultimate Boundness(SGUUB).Finally,the efficacy and superiority of the developed control strategy are confirmed by simulation results.展开更多
Objective:To investigate the impact of precise nursing care based on dynamic nursing quality feedback model on the postoperative recovery of elderly patients undergoing radical resection for colon cancer,with a partic...Objective:To investigate the impact of precise nursing care based on dynamic nursing quality feedback model on the postoperative recovery of elderly patients undergoing radical resection for colon cancer,with a particular focus on its effects on psychological flexibility.Methods:Medical records of 124 elderly patients undergoing radical resection for colon cancer at The First Affiliated Hospital of Baotou Medical College between January 2021 and May 2024 were retrospectively analyzed in this study.Based on the received nursing interventions,the patients were divided into a control group(standard nursing care)and an observation group(precise nursing care based on a dynamic nursing quality feedback model).Results:The observation group exhibited significantly higher levels of hemoglobin,prealbumin,and albumin compared to the control group.Additionally,the observation group had lower scores in somatization,interpersonal sensitivity,depression,anxiety,obsessions-compulsions,hostility,phobic anxiety,psychoticism,and paranoid ideation.The observation group also demonstrated higher scores in active coping,self-efficacy,and the management of emotions,life,and symptoms.Improvements were also observed in nursing quality,perioperative intervention,satisfaction with rehabilitation guidance,and awareness of regular reexaminations,diet intervention,and complication prevention(all with P<0.05).Conclusion:Precise nursing based on a dynamic nursing quality feedback model can improve nutritional status and medical coping style,reduce psychological issues,and enhance self-management abilities in elderly patients following radical resection of colon cancer.Additionally,it increases nursing satisfaction and raises awareness regarding the importance of regular reexaminations and complication prevention.展开更多
Accurate Electric Load Forecasting(ELF)is crucial for optimizing production capacity,improving operational efficiency,and managing energy resources effectively.Moreover,precise ELF contributes to a smaller environment...Accurate Electric Load Forecasting(ELF)is crucial for optimizing production capacity,improving operational efficiency,and managing energy resources effectively.Moreover,precise ELF contributes to a smaller environmental footprint by reducing the risks of disruption,downtime,and waste.However,with increasingly complex energy consumption patterns driven by renewable energy integration and changing consumer behaviors,no single approach has emerged as universally effective.In response,this research presents a hybrid modeling framework that combines the strengths of Random Forest(RF)and Autoregressive Integrated Moving Average(ARIMA)models,enhanced with advanced feature selection—Minimum Redundancy Maximum Relevancy and Maximum Synergy(MRMRMS)method—to produce a sparse model.Additionally,the residual patterns are analyzed to enhance forecast accuracy.High-resolution weather data from Weather Underground and historical energy consumption data from PJM for Duke Energy Ohio and Kentucky(DEO&K)are used in this application.This methodology,termed SP-RF-ARIMA,is evaluated against existing approaches;it demonstrates more than 40%reduction in mean absolute error and root mean square error compared to the second-best method.展开更多
The effect of real-time high temperature and thermal treatment on the mechanical characteristics and crack evolution of granite with different grain sizes(i.e.,0.5 mm,0.7 mm and 1.0 mm)is investigated by numerical sim...The effect of real-time high temperature and thermal treatment on the mechanical characteristics and crack evolution of granite with different grain sizes(i.e.,0.5 mm,0.7 mm and 1.0 mm)is investigated by numerical simulation employing a grain-based model,and the impact of initial cracks on thermal-induced strengthening is also examined by integrating random cracks within the model before tests.The results revealed that thermal stress,induced by the mismatch in thermal expansion coefficient between various minerals,is the primary distinction between rock specimens in real-time high temperature and thermal treatment.With increasing temperature,the thermal stress gradually accumulates in quartz minerals under real-time high temperature but releases after thermal treatment.The high local contact force significantly affects the peak stress and crack evolution.Uniaxial compression simulation results demonstrate that progressive accumulation of thermal stress induces degradation in macroscopic peak strength and increase of microcrack density.The grain size controls the ratio of intergranular contacts to intragranular contacts,and leads to an increase in strong contact number in the intragrain and a decrease in strong contact number in the intergrain.The strengthening of uniaxial compression strength in the experiment can be well simulated by controlling the number of pre-existing initial cracks in the numerical model.Our conclusions are beneficial to a better understanding of the underlying mechanisms of thermal damage and thermal strengthening of granite for deep geological engineering.展开更多
To improve the accuracy of rockburst risk evaluation in mining and tunnelling engineering,the influence of intermediate principal stress σ_(2) deserves further consideration,which has been neglected in general predic...To improve the accuracy of rockburst risk evaluation in mining and tunnelling engineering,the influence of intermediate principal stress σ_(2) deserves further consideration,which has been neglected in general prediction frameworks.This study employs an integrated approach that combines true-triaxial unloading experiments with three-dimensional grain-based discrete element modeling(PFC3D-GBM)to examine the effects of σ_(2) on strain systematically burst and elucidate the underlying mechanisms.Through this dual experimental–numerical methodology,the strainburst characteristics under varying σ_(2) are analyzed in detail regarding mechanical responses,failure evolution and patterns,microscope fracture mechanisms,and energy partitioning.The results indicate that elevated σ_(2) can enhance the bearing capacity of rock,thereby necessitating a higher stress condition required for strainburst.However,it also enlarges the potential strainburst intensity,manifesting as deeper rockburst pits and more violent ejection of rock fragments.An increasing σ_(2) facilitates the microscope transgranular fractures,inhibits intergranular tensile fractures,and raises the kinetic energy conversion ratio slightly.It affects the intensity of strainburst through the following mechanisms,including the increase of energy storage limit,the intensification of Poisson effect for lateral expansion,and the enhancement of the transgranular fracturing mechanism.In practical engineering,the depth and range of support needs to be ensured under high σ_(2) conditions,and it is recommended to use prestressing techniques to control the development of significant slabbing.展开更多
The fatigue resistance and wear performance of aviation gears under extreme conditions(e.g.,high speed and heavy load)are closely related to tooth surface topography.Establishing an accurate correlation between surfac...The fatigue resistance and wear performance of aviation gears under extreme conditions(e.g.,high speed and heavy load)are closely related to tooth surface topography.Establishing an accurate correlation between surface topography and service performance requires numerous topography samples.Grinding-shot peening(GSP)combined processes are the key processes for manufacturing aviation gears.展开更多
As the core component of energy conversion for large wind turbines,the output performance of doubly-fed induction generators (DFIGs) plays a decisive role in the power quality of wind turbines.To realize the fast and ...As the core component of energy conversion for large wind turbines,the output performance of doubly-fed induction generators (DFIGs) plays a decisive role in the power quality of wind turbines.To realize the fast and accurate design optimization of DFIGs,this paper proposes a novel hybriddriven surrogate-assisted optimization method.It firstly establishes an accurate subdomain model of DFIGs to analytically predict performance indexes.Furthermore,taking the inexpensive analytical dataset produced by the subdomain model as the source domain and the expensive finite element analysis dataset as the target domain,a high-precision surrogate model is trained in a transfer learning way and used for the subsequent multi-objective optimization process.Based on this model,taking the total harmonic distortion of electromotive force,cogging torque,and iron loss as objectives,and the slot and inner/outer diameters as parameters for optimizing the topology,achieve a rapid and accurate electromagnetic design for DFIGs.Finally,experiments are carried out on a 3MW DFIG to validate the effectiveness of the proposed method.展开更多
The integration and development of grass-roots Party organizations and accurate poverty alleviation is the focus in social development in the new period. This is also a new measure explored by the CPC Central Committe...The integration and development of grass-roots Party organizations and accurate poverty alleviation is the focus in social development in the new period. This is also a new measure explored by the CPC Central Committee in the new historical period to solve rural reform and extricate the poor from poverty,and can effectively enhance the enthusiasm of the masses in poverty alleviation and development work. Xundian Hui and Yi Autonomous County is located in the mountainous area of northeast Yunnan Province. It is one of the 592 national key counties for poverty alleviation and development and one of the 38 continuous development counties in Wumeng Mountain area. Since the implementation of the accurate poverty alleviation strategy,Xundian County insists on getting rid of poverty to grasp the overall situation of county economic and social development,focus on the actual situation of the county people,and conscientiously grasp the key of industrial poverty alleviation. It regards industry as the fundamental driving force to realize poverty alleviation from " blood transfusion" to " blood creation",and innovates the model of " Party branch +" to help the poor out of poverty by industry. It has selected 187 agricultural enterprises( cooperatives,large households) to achieve full coverage of all registered poor households,and achieved remarkable results. It has realized that each poor village has one to two leading industries,and each poor household has one to two industrial income projects,having led 30 500 poor households to increase their average income by more than 1 850 yuan. The final incidence of poverty decreased from 26. 93% in 2014 to 0. 35% at the end of 2017,becoming one of the first counties in Yunnan Province to get rid of poverty. It is also the only county in Yunnan Province that has won the Antipoverty Organization Innovation Award of the State Council. Based on field research and interviews,this paper analyzes and summarizes the specific methods,main achievements,practical experience and popularization and application measures of Xundian County " Party Branch +" to promote industrial poverty alleviation,so as to provide necessary reference for accurate poverty reduction and poverty alleviation in similar mountainous areas of Yunnan Province and other provinces.展开更多
文摘The exploration of Mars would heavily rely on Martian rocks mechanics and engineering technology.As the mechanical property of Martian rocks is uncertain,it is of utmost importance to predict the probability distribution of Martian rocks mechanical property for the success of Mars exploration.In this paper,a fast and accurate probability distribution method for predicting the macroscale elastic modulus of Martian rocks was proposed by integrating the microscale rock mechanical experiments(micro-RME),accurate grain-based modeling(AGBM)and upscaling methods based on reliability principles.Firstly,the microstructure of NWA12564 Martian sample and elastic modulus of each mineral were obtained by micro-RME with TESCAN integrated mineral analyzer(TIMA)and nanoindentation.The best probability distribution function of the minerals was determined by Kolmogorov-Smirnov(K-S)test.Secondly,based on best distribution function of each mineral,the Monte Carlo simulations(MCS)and upscaling methods were implemented to obtain the probability distribution of upscaled elastic modulus.Thirdly,the correlation between the upscaled elastic modulus and macroscale elastic modulus obtained by AGBM was established.The accurate probability distribution of the macroscale elastic modulus was obtained by this correlation relationship.The proposed method can predict the probability distribution of Martian rocks mechanical property with any size and shape samples.
基金in part supported by the National Natural Science Foundation of China(Grant Nos.41877217 and 51609178)the General Research Fund of the Research Grants Council(Hong Kong,China)(Grant No.17303917)the Singapore Academic Research Fund Tier 1 Grant(RG112/14).
文摘Grain size effect on rock strength is a topic of great interest in geotechnical engineering.A consensus obtained from earlier laboratory tests is that rock strength generally decreases with the increase of grain size for both silicate and carbonate rocks;however,some recent numerical results conflict with such laboratory test results.To address this intriguing issue,the effect of grain size on strength of polymineralic crystalline rock with low porosity is investigated numerically using the grain-based modeling(GBM)approach in discrete element method(DEM)by interpreting micro-cracking process in response to loading.In agreement with some previous DEM simulation results,the simulated rock strength is found to increase with increasing grain size for both homogeneous and heterogeneous models,even when the number of assembled disks in one mineral grain changes.The mechanism of strength increase with increasing grain size is mainly associated with the number of assembled smooth-joint contacts along grain interfaces and the generation of grain boundary cracks in response to loading.The grain interfaces significantly weaken the integrity of the rock model,which is similar to effects of inherent defects in real rock.As the grain size increases,fewer grain interfaces are built in the model and the rock strength becomes much higher.Hence,by solely changing the mineral grain size in a model,the mechanism of grain size effect as observed in laboratory tests cannot be replicated.To address this issue,a method of degradation of grain boundary strength parameters is used to mimic the possible mechanism of grain size effect.The simulated strength using the method becomes comparable with those obtained from laboratory tests when the heterogeneity in the rock is considered.Degradation of grain boundary parameters with increasing grain size provides a plausible explanation for the grain size effect on rock strength.
基金supported by the Project of National Natural Science Foundation of China under Grant 52077122。
文摘With the continuous upgrading of traditional manufacturing industries and the rapid rise of emerging technology fields,the performance requirements for the permanent magnet synchronous motors(PMSMs)have become higher and higher.The importance of fast and accurate electromagnetic thermal coupling analysis of such motors becomes more and more prominent.In view of this,the surfacemounted PMSM(SPMSM)equipped with unequally thick magnetic poles is taken as the main object and its electromagnetic thermal coupling analytical model(ETc AM)is investigated.First,the electromagnetic analytical model(EAM)is studied based on the modified subdomain method.It realizes the fast calculation of key electromagnetic characteristics.Subsequently,the 3D thermal analytical model(TAM)is developed by combining the EAM,the lumped parameter thermal network method(LPTNM),and the partial differential equation of heat flux.It realizes the fast calculation of key thermal characteristics in 3D space.Further,the information transfer channel between EAM and TAM is built with reference to the intrinsic connection between electromagnetic field and temperature field.Thereby,the novel ETcAM is proposed to realize the fast and accurate prediction of electromagnetic and temperature fields.Besides,ETcAM has a lot to commend it.One is that it well accounts for the complex structure,saturation,and heat exchange behavior.Second,it saves a lot of computer resources.It offers boundless possibilities for initial design,scheme evaluation,and optimization of motors.Finally,the validity,accuracy,and practicality of this study are verified by simulation and experiment.
基金supported by Guangzhou Science and Technology Planning Project(2023A04J0131)Special fund for scientific innovation strategyconstruction of high level Academy of Agriculture Science(R2020PY-JG009,R2022PY-QY007,202106TD)+2 种基金China Agriculture Research System-CARS-35the Project of Swine Innovation Team in Guangdong Modern Agricultural Research System(2022KJ126)Special Fund for Rural Revitalization Strategy of Guangdong(2023TS-3),China。
文摘Oxidative stress has been associated with a number of physiological problems in swine,including reduced production efficiency.Recently,although there has been increased research into regulatory mechanisms and antioxidant strategies in relation to oxidative stress-induced pig production,it remains so far largely unsuccessful to develop accurate models and nutritional strategies for specific oxidative stress factors.Here,we discuss the dose and dose intensity of the causes of oxidative stress involving physiological,environmental and dietary factors,recent research models and the antioxidant strategies to provide theoretical guidance for future oxidative stress research in swine.
文摘A grain-based distinct element model featuring three-dimensional （3D） Voronoi tessellations （randompoly-crystals） is proposed for simulation of crack damage development in brittle rocks. The grainboundaries in poly-crystal structure produced by Voronoi tessellations can represent flaws in intact rockand allow for numerical replication of crack damage progression through initiation and propagation ofmicro-fractures along grain boundaries. The Voronoi modelling scheme has been used widely in the pastfor brittle fracture simulation of rock materials. However the difficulty of generating 3D Voronoi modelshas limited its application to two-dimensional （2D） codes. The proposed approach is implemented inNeper, an open-source engine for generation of 3D Voronoi grains, to generate block geometry files thatcan be read directly into 3DEC. A series of Unconfined Compressive Strength （UCS） tests are simulated in3DEC to verify the proposed methodology for 3D simulation of brittle fractures and to investigate therelationship between each micro-parameter and the model＇s macro-response. The possibility of numericalreplication of the classical U-shape strength curve for anisotropic rocks is also investigated innumerical UCS tests by using complex-shaped （elongated） grains that are cemented to one another alongtheir adjoining sides. A micro-parameter calibration procedure is established for 3D Voronoi models foraccurate replication of the mechanical behaviour of isotropic and anisotropic （containing a fabric） rocks. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.
文摘The objective of this paper is to develop a methodology for calibration of a discrete element grain-based model(GBM)to replicate the hydro-mechanical properties of a brittle rock measured in the laboratory,and to apply the calibrated model to simulating the formation of excavation damage zone(EDZ)around underground excavations.Firstly,a new cohesive crack model is implemented into the universal distinct element code(UDEC)to control the fracturing behaviour of materials under various loading modes.Next,a methodology for calibration of the components of the UDEC-Voronoi model is discussed.The role of connectivity of induced microcracks on increasing the permeability of laboratory-scale samples is investigated.The calibrated samples are used to investigate the influence of pore fluid pressure on weakening the drained strength of the laboratory-scale rock.The validity of the Terzaghi’s effective stress law for the drained peak strength of low-porosity rock is tested by performing a series of biaxial compression test simulations.Finally,the evolution of damage and pore pressure around two unsupported circular tunnels in crystalline granitic rock is studied.
文摘:A new accurate algorithms based on mathematical modeling of two parallel transmissions lines system(TPTLS)as influenced by the mutual effect to determine the fault location is discussed in this work.The distance relay measures the impedance to the fault location which is the positive-sequence.The principle of summation the positive-,negative-,and zero-sequence voltages which equal zero is used to determine the fault location on the TPTLS.Also,the impedance of the transmission line to the fault location is determined.These algorithms are applied to single-line-to-ground(SLG)and double-line-to-ground(DLG)faults.To detect the fault location along the transmission line,its impedance as seen by the distance relay is determined to indicate if the fault is within the relay’s reach area.TPTLS under study are fed from one-and both-ends.A schematic diagrams are obtained for the impedance relays to determine the fault location with high accuracy.
文摘Viscosity of natural gas is a basic and important parameter,of theoretical and practical significance in the domain of natural gas recovery,transmission and processing.In order to obtain the accurate viscosity data efficiently at a low cost,a new model and its corresponding functional relation are derived on the basis of the relationship among viscosity,temperature and density derived from the kinetic theory of gases.After the model parameters were optimized using a lot of experimental data,the diagram showing the variation of viscosity along with temperature and density is prepared,showing that:①the gas viscosity increases with the increase of density as well as the increase of temperature in the low density region;②the gas viscosity increases with the decrease of temperature in high density region.With this new model,the viscosity of 9 natural gas samples was calculated precisely.The average relative deviation between these calculated values and 1539 experimental data measured at 250e450 K and 0.10e140.0 MPa is less than 1.9%.Compared with the 793 experimental data with a measurement error less than 0.5%,the maximum relative deviation is less than 0.98%.It is concluded that this new model is more advantageous than the previous 8 models in terms of simplicity,accuracy,fast calculation,and direct applicability to the CO_(2) bearing gas samples.
基金supported by the Natural Science Basic Research Program of Shaanxi Province,China(No.2019JQ-711)。
文摘A novel accurate tracking controller is developed for the longitudinal dynamics of Hypersonic Flight Vehicles(HFVs)in the presence of large model uncertainties,external disturbances and actuator nonlinearities.Distinct from the state-of-the-art,besides being continuity,no restrictive conditions have been imposed on the HFVs dynamics.The system uncertainties are skillfully handled by being seen as bounded"disturbance terms".In addition,by means of backstepping adaptive technique,the accurate tracking(i.e.tracking errors converge to zero as time approaches infinity)rather than bounded tracking(i.e.tracking errors converge to residual sets)has been achieved.What’s more,the accurate tracking problems for HFVs subject to actuator dead-zone and hysteresis are discussed,respectively.Then,all signals of closed-loop system are verified to be Semi-Global Uniformly Ultimate Boundness(SGUUB).Finally,the efficacy and superiority of the developed control strategy are confirmed by simulation results.
文摘Objective:To investigate the impact of precise nursing care based on dynamic nursing quality feedback model on the postoperative recovery of elderly patients undergoing radical resection for colon cancer,with a particular focus on its effects on psychological flexibility.Methods:Medical records of 124 elderly patients undergoing radical resection for colon cancer at The First Affiliated Hospital of Baotou Medical College between January 2021 and May 2024 were retrospectively analyzed in this study.Based on the received nursing interventions,the patients were divided into a control group(standard nursing care)and an observation group(precise nursing care based on a dynamic nursing quality feedback model).Results:The observation group exhibited significantly higher levels of hemoglobin,prealbumin,and albumin compared to the control group.Additionally,the observation group had lower scores in somatization,interpersonal sensitivity,depression,anxiety,obsessions-compulsions,hostility,phobic anxiety,psychoticism,and paranoid ideation.The observation group also demonstrated higher scores in active coping,self-efficacy,and the management of emotions,life,and symptoms.Improvements were also observed in nursing quality,perioperative intervention,satisfaction with rehabilitation guidance,and awareness of regular reexaminations,diet intervention,and complication prevention(all with P<0.05).Conclusion:Precise nursing based on a dynamic nursing quality feedback model can improve nutritional status and medical coping style,reduce psychological issues,and enhance self-management abilities in elderly patients following radical resection of colon cancer.Additionally,it increases nursing satisfaction and raises awareness regarding the importance of regular reexaminations and complication prevention.
基金supported by the Startup Grant(PG18929)awarded to F.Shokoohi.
文摘Accurate Electric Load Forecasting(ELF)is crucial for optimizing production capacity,improving operational efficiency,and managing energy resources effectively.Moreover,precise ELF contributes to a smaller environmental footprint by reducing the risks of disruption,downtime,and waste.However,with increasingly complex energy consumption patterns driven by renewable energy integration and changing consumer behaviors,no single approach has emerged as universally effective.In response,this research presents a hybrid modeling framework that combines the strengths of Random Forest(RF)and Autoregressive Integrated Moving Average(ARIMA)models,enhanced with advanced feature selection—Minimum Redundancy Maximum Relevancy and Maximum Synergy(MRMRMS)method—to produce a sparse model.Additionally,the residual patterns are analyzed to enhance forecast accuracy.High-resolution weather data from Weather Underground and historical energy consumption data from PJM for Duke Energy Ohio and Kentucky(DEO&K)are used in this application.This methodology,termed SP-RF-ARIMA,is evaluated against existing approaches;it demonstrates more than 40%reduction in mean absolute error and root mean square error compared to the second-best method.
基金Project(51879135)supported by the Taishan Scholars Program,ChinaProject(52309130)supported by the National Natural Science Foundation of China+1 种基金Project(SKLGME023003)supported by the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering Safety,ChinaProject(2022AH051754)supported by the Natural Science Research Project of Anhui Universities,China。
文摘The effect of real-time high temperature and thermal treatment on the mechanical characteristics and crack evolution of granite with different grain sizes(i.e.,0.5 mm,0.7 mm and 1.0 mm)is investigated by numerical simulation employing a grain-based model,and the impact of initial cracks on thermal-induced strengthening is also examined by integrating random cracks within the model before tests.The results revealed that thermal stress,induced by the mismatch in thermal expansion coefficient between various minerals,is the primary distinction between rock specimens in real-time high temperature and thermal treatment.With increasing temperature,the thermal stress gradually accumulates in quartz minerals under real-time high temperature but releases after thermal treatment.The high local contact force significantly affects the peak stress and crack evolution.Uniaxial compression simulation results demonstrate that progressive accumulation of thermal stress induces degradation in macroscopic peak strength and increase of microcrack density.The grain size controls the ratio of intergranular contacts to intragranular contacts,and leads to an increase in strong contact number in the intragrain and a decrease in strong contact number in the intergrain.The strengthening of uniaxial compression strength in the experiment can be well simulated by controlling the number of pre-existing initial cracks in the numerical model.Our conclusions are beneficial to a better understanding of the underlying mechanisms of thermal damage and thermal strengthening of granite for deep geological engineering.
基金supported by the National Natural Science Foundation of China(No.42507210)the Fundamental Research Funds for the Central Universities(No.2025XJSB01)+1 种基金the State Key Laboratory for Tunnel Engineering(No.SKLTEK202421)the Foundation of Key Laboratory of Deep Coal Resource Mining(China University of Mining and Technology),Ministry of Education(No.KLDCRMMOE24KF11).
文摘To improve the accuracy of rockburst risk evaluation in mining and tunnelling engineering,the influence of intermediate principal stress σ_(2) deserves further consideration,which has been neglected in general prediction frameworks.This study employs an integrated approach that combines true-triaxial unloading experiments with three-dimensional grain-based discrete element modeling(PFC3D-GBM)to examine the effects of σ_(2) on strain systematically burst and elucidate the underlying mechanisms.Through this dual experimental–numerical methodology,the strainburst characteristics under varying σ_(2) are analyzed in detail regarding mechanical responses,failure evolution and patterns,microscope fracture mechanisms,and energy partitioning.The results indicate that elevated σ_(2) can enhance the bearing capacity of rock,thereby necessitating a higher stress condition required for strainburst.However,it also enlarges the potential strainburst intensity,manifesting as deeper rockburst pits and more violent ejection of rock fragments.An increasing σ_(2) facilitates the microscope transgranular fractures,inhibits intergranular tensile fractures,and raises the kinetic energy conversion ratio slightly.It affects the intensity of strainburst through the following mechanisms,including the increase of energy storage limit,the intensification of Poisson effect for lateral expansion,and the enhancement of the transgranular fracturing mechanism.In practical engineering,the depth and range of support needs to be ensured under high σ_(2) conditions,and it is recommended to use prestressing techniques to control the development of significant slabbing.
基金supported by the National Natural Science Foundation of China(Grant No.U22B2086)。
文摘The fatigue resistance and wear performance of aviation gears under extreme conditions(e.g.,high speed and heavy load)are closely related to tooth surface topography.Establishing an accurate correlation between surface topography and service performance requires numerous topography samples.Grinding-shot peening(GSP)combined processes are the key processes for manufacturing aviation gears.
文摘As the core component of energy conversion for large wind turbines,the output performance of doubly-fed induction generators (DFIGs) plays a decisive role in the power quality of wind turbines.To realize the fast and accurate design optimization of DFIGs,this paper proposes a novel hybriddriven surrogate-assisted optimization method.It firstly establishes an accurate subdomain model of DFIGs to analytically predict performance indexes.Furthermore,taking the inexpensive analytical dataset produced by the subdomain model as the source domain and the expensive finite element analysis dataset as the target domain,a high-precision surrogate model is trained in a transfer learning way and used for the subsequent multi-objective optimization process.Based on this model,taking the total harmonic distortion of electromotive force,cogging torque,and iron loss as objectives,and the slot and inner/outer diameters as parameters for optimizing the topology,achieve a rapid and accurate electromagnetic design for DFIGs.Finally,experiments are carried out on a 3MW DFIG to validate the effectiveness of the proposed method.
基金Supported by the Construction Project of Party Branch Secretary’s Studio of "Double Leader" Teachers in Colleges and Universities of the Ministry of Education of ChinaThe Project of Party Construction Research of Yunnan University of Finance and Economics
文摘The integration and development of grass-roots Party organizations and accurate poverty alleviation is the focus in social development in the new period. This is also a new measure explored by the CPC Central Committee in the new historical period to solve rural reform and extricate the poor from poverty,and can effectively enhance the enthusiasm of the masses in poverty alleviation and development work. Xundian Hui and Yi Autonomous County is located in the mountainous area of northeast Yunnan Province. It is one of the 592 national key counties for poverty alleviation and development and one of the 38 continuous development counties in Wumeng Mountain area. Since the implementation of the accurate poverty alleviation strategy,Xundian County insists on getting rid of poverty to grasp the overall situation of county economic and social development,focus on the actual situation of the county people,and conscientiously grasp the key of industrial poverty alleviation. It regards industry as the fundamental driving force to realize poverty alleviation from " blood transfusion" to " blood creation",and innovates the model of " Party branch +" to help the poor out of poverty by industry. It has selected 187 agricultural enterprises( cooperatives,large households) to achieve full coverage of all registered poor households,and achieved remarkable results. It has realized that each poor village has one to two leading industries,and each poor household has one to two industrial income projects,having led 30 500 poor households to increase their average income by more than 1 850 yuan. The final incidence of poverty decreased from 26. 93% in 2014 to 0. 35% at the end of 2017,becoming one of the first counties in Yunnan Province to get rid of poverty. It is also the only county in Yunnan Province that has won the Antipoverty Organization Innovation Award of the State Council. Based on field research and interviews,this paper analyzes and summarizes the specific methods,main achievements,practical experience and popularization and application measures of Xundian County " Party Branch +" to promote industrial poverty alleviation,so as to provide necessary reference for accurate poverty reduction and poverty alleviation in similar mountainous areas of Yunnan Province and other provinces.
