Laboratory pull-out tests were conducted on the following rock bolts and cable bolts:steel rebars,smooth steel bars,fiberglass reinforced polymer threaded bolts,flexible cable bolts,IR5/IN special cable bolts and Mini...Laboratory pull-out tests were conducted on the following rock bolts and cable bolts:steel rebars,smooth steel bars,fiberglass reinforced polymer threaded bolts,flexible cable bolts,IR5/IN special cable bolts and Mini-cage cable bolts.The diameter of the tested bolts was between 16 mm and 26 mm.The bolts were grouted in a sandstone sample using resin or cement grouts.The tests were conducted under either constant radial stiffness or constant confining pressure boundary conditions applied on the outer surface of the rock sample.In most tests,the rate of displacement was about 0.02 mm/s.The tests were performed using a pull-out bench that allows testing a wide range of parameters.This paper provides an extensive database of laboratory pull-out test results and confirms the influence of the confining pressure and the embedment length on the pull-out response(rock bolts and cable bolts).It also highlights the sensitivity of the results to the operating conditions and to the behavior of the sample as a whole,which cannot be neglected when the test results are used to assess the bolt-grout or the grouterock interface.展开更多
A major dilemma faced in the nuclear industry is repair of stainless steel reactor components that have been exposed to neutron irradiation. When conventional fusion welding is used for repair, intergranular cracks de...A major dilemma faced in the nuclear industry is repair of stainless steel reactor components that have been exposed to neutron irradiation. When conventional fusion welding is used for repair, intergranular cracks develop in the heat-affected zone(HAZ). Friction stir processing(FSP), which operates at much lower peak temperatures than fusion welding, was studied as a crack repair method for irradiated 304 L stainless steel. A numerical simulation of the FSP process in 304 L was developed to predict temperatures and recrystallized grain size in the stir zone. The model employed an Eulerian finite element approach,where flow stresses for a large range of strain rates and temperatures inherent in FSP were used as input. Temperature predictions in three locations near the stir zone were accurate to within 4%, while prediction of welding power was accurate to within 5% of experimental measurements. The predicted recrystallized grain sizes ranged from 7.6 to 10.6 μm, while the experimentally measured grains sizes in the same locations ranged from 6.0 to 7.6 μm. The maximum error in predicted recrystallized grain size was about 39%, but the associated stir zone hardness from the predicted grain sizes was only different from the experiment by about 10%.展开更多
Charnockites sensu lato （charnockite-enderbite series） are lower crustal felsic rocks typically characterised by the presence of anhydrous minerals including orthopyroxene and garnet. They either represent dry （H2O...Charnockites sensu lato （charnockite-enderbite series） are lower crustal felsic rocks typically characterised by the presence of anhydrous minerals including orthopyroxene and garnet. They either represent dry （H2O-poor） felsic magmas that are emplaced in the lower crust or granitic intrusions that have been dehydrated during a subsequent granulite facies metamorphic event. In the first case, post- magmatic high-temperature recrystallisation may result in widespread metamorphic granulite microstruc- tures, superimposed or replacing the magmatic microstructures. Despite recrystallisation, magmatic remnants may still be found, notably in the form of melt-related microstructures such as melt inclusions. For both magmatic charnockites and dehydrated granites, subsequent fluid-mineral interaction at inter- grain boundaries during retrogradation are documented by microstructures including K-feldspar micro- veins and myrmekites. They indicate that a large quantity of low-H2O activity salt-rich brines, were present （together with CO2 under immiscible conditions） in the lower crust.展开更多
This paper proposes a new interface constitutive model for fully grouted rock-bolts and cable-bolts based on pull-out test results.A database was created combining published experimental data with in-house tests.By me...This paper proposes a new interface constitutive model for fully grouted rock-bolts and cable-bolts based on pull-out test results.A database was created combining published experimental data with in-house tests.By means of a comprehensive framework,a Coulomb-type failure criterion accounting for friction mobilization was defined.During the elastic phase,in which the interface joint is not yet created,the proposed model provides zero radial displacement,and once the interface joint is created,interface dilatancy is modeled using a non-associated plastic potential inspired from the behavior of rock joints.The results predicted by the proposed model are in good agreement with experimental results.The model has been implemented in a finite element method(FEM)code and numerical simulations have been performed at the elementary and the structural scales.The results obtained provide confidence in the ability of the new model to assist in the design and optimization of bolting patterns.展开更多
The article focuses on the design and application of an active reconfigurable controller that mitigates the effects of gust load and actuator faults on a flexible aircraft.A novel integrated adaptive output feedback s...The article focuses on the design and application of an active reconfigurable controller that mitigates the effects of gust load and actuator faults on a flexible aircraft.A novel integrated adaptive output feedback scheme is investigated to address the actuator faults.The real-time fault values provided by the fault estimation module are considered in the reconfigurable control law to improve the fault-tolerant capability.The estimate values of faults and control gains are calculated by analyzing the stability of the overall system.The proposed controller is simulated using a flexible aircraft model with a discrete‘1-cosine’gust,and the results show that it can effectively mitigate the wing root moments and recover the flight maneuver stability after the aircraft suffered from gusts.展开更多
An integrated dynamic model of natural gas pipeline networks is developed in this paper.Components for gas supply,e.g.,pipelines,junctions,compressor stations,LNG terminals,regulation stations and gas storage faciliti...An integrated dynamic model of natural gas pipeline networks is developed in this paper.Components for gas supply,e.g.,pipelines,junctions,compressor stations,LNG terminals,regulation stations and gas storage facilities are included in the model.These components are firstly modeled with respect to their properties and functions and,then,integrated at the system level by Graph Theory.The model can be used for simulating the system response in different scenarios of operation,and evaluate the consequences from the perspectives of supply security and resilience.A case study is considered to evaluate the accuracy of the model by benchmarking its results against those from literature and the software Pipeline Studio.Finally,the model is applied on a relatively complex natural gas pipeline network and the results are analyzed in detail from the supply security and resilience points of view.The main contributions of the paper are:firstly,a novel model of a complex gas pipeline network is proposed as a dynamic state-space model at system level;a method,based on the dynamic model,is proposed to analyze the security and resilience of supply from a system perspective.展开更多
Recently,stress-based dilatancy criteria have become essential tools to design underground facilities in salt formations such as gas storage caverns.However,these criteria can depend critically on the volumetric strai...Recently,stress-based dilatancy criteria have become essential tools to design underground facilities in salt formations such as gas storage caverns.However,these criteria can depend critically on the volumetric strain measurements used to deduce the dilatancy onset.Results from conventional triaxial compression tests can show different volumetric behavior depending on the loading conditions,as well as on the measurement techniques.In order to obtain a quantitative understanding of this problem,an experimental program was carried out and the testing procedure was investigated numerically under homogeneous and heterogeneous stress states.The experimental results showed that the deviatoric stress corresponding to the dilatancy onset was significantly dependent on the measurement techniques.With a heterogeneous stress state,the simulation results revealed that the strain measurements at different scales (referred to as local,hybrid or global) can provide different volumetric results with moderate to significant deviations from the idealized behavior,and hence different onsets of dilatancy.They also proved that,under low confinement,tensile stresses can take place within the compressed specimen,leading to a great deviation of the dilatancy onset from the idealized behavior.From both experimental and numerical investigations,the difference in sensitivity to the measurement techniques between the deviatoric and the volumetric behaviors is explained by the relatively small values of the volumetric strain.The non-ideal laboratory conditions have more impact on this strain than on the deviatoric one.These findings can have implications for the interpretation of the dilatancy behavior of rock salt,and hence on the geomechanical design aspects in salt formations.展开更多
The degradation of components in complex mechatronic systems involves multiple physical processes which will cause coupling interactions among nodes in the system.The interaction of nodes may be carried out not only b...The degradation of components in complex mechatronic systems involves multiple physical processes which will cause coupling interactions among nodes in the system.The interaction of nodes may be carried out not only by physical connections but also by the environment which cannot be described by single network using the traditional methods.In order to give out a unified model to quantitatively describe the coupling degradation spreading by both physical connections and environment,a novel Energy-Flow-Field Network(EFFN)and a coupling degradation model based on EFFN are proposed in this paper.The EFFN is driven by energy flow and the state transition of spatially related nodes is triggered by the dissipation energy.An application is conducted on aviation actuation system in which the degradation spreading by fluid-thermal-solid interaction is considered.The degradation path and the most probable fault reason can be obtained by combining the state transition and energy output of nodes,which is consistent with the given scenario.展开更多
This paper investigates the electrical and mechanical behaviors of a single-ASDBD actuator and a two-ASDBD one supplied in sinusoidal mode（1-10 kHz）.The main objective of our research is to determine the optimum fre...This paper investigates the electrical and mechanical behaviors of a single-ASDBD actuator and a two-ASDBD one supplied in sinusoidal mode（1-10 kHz）.The main objective of our research is to determine the optimum frequency values for the function of these actuators with a given power supply.For this purpose,we determine the electrical power density input to the actuators versus frequency through two methods：i） a semi-theoretical method,based on an impedance calculation,and ii） an experimental method,based on direct electrical measurements.These methods show that the addition of a second ASDBD changes the resonance frequency value of the actuator by moving it towards low frequencies.After characterizing the aerodynamic mobile layer structure induced by the single-ASDBD actuator,we analyze experimentally the mechanical response of a two-ASDBD actuator as a function of the inter-ASDBD distance.The experiments demonstrate that the induced electric wind velocity and the electro-mechanical yield of a twoASDBD actuator reach a maximum value for an optimum inter-ASDBD distance,which is a useful value for the design of highly efficient multi-ASDBD actuators.展开更多
The goal of this article is dual： first, introducing a new model of accident named STAMP （systems-theoretic accident modeling and processes）; then applying the model to an innovative process for the treatment of co...The goal of this article is dual： first, introducing a new model of accident named STAMP （systems-theoretic accident modeling and processes）; then applying the model to an innovative process for the treatment of contaminated substances and the re-use of treated substances. This article is a demonstration for a need of a new tool to take into account hazards and safety within socio-technical systems.展开更多
The dislocation density tensor computed as the cud of plastic distortion is regarded as a new constitutive variable in crystal plasticity. The dependence of the free energy function on the dislocation density tensor i...The dislocation density tensor computed as the cud of plastic distortion is regarded as a new constitutive variable in crystal plasticity. The dependence of the free energy function on the dislocation density tensor is explored starting from a quadratic ansatz. Rank one and logarithmic dependencies are then envisaged based on considerations from the statistical theory of dislocations. The rele- vance of the presented free energy potentials is evaluated from the corresponding analytical solutions of the periodic two-phase laminate problem under shear where one layer is a single crystal material undergoing single slip and the second one remains purely elastic.展开更多
This paper focuses on the presence of nodules of insoluble materials within salt specimens,and their effect on the volumetric strain measurements and the dilatancy phenomenon.We analyzed experimental results of over 1...This paper focuses on the presence of nodules of insoluble materials within salt specimens,and their effect on the volumetric strain measurements and the dilatancy phenomenon.We analyzed experimental results of over 120 conventional triaxial compression tests,and found that in 20%of the cases,the volumetric strain measurements were atypical.We also noted that the natural variability of the specimens can lead to a non-negligible data scattering in the volumetric strain measurements when different specimens are subjected to the same test.This is expected given the small magnitude of those strains,but it occasionally implies that the corresponding specimens are not representative of the volumetric behavior of the studied rock.In order to understand these results,we numerically investigated salt specimens modeled as halite matrices with inclusions of impurities.Simulations of triaxial compression tests on these structures proved that such heterogeneities can induce dilatancy,and their presence can lead to the appearance of tensile zones which is physically translated into a micro-cracking activity.The modeling approach is validated as the patterns displayed in the numerical results are identical to that in the laboratory.It was then employed to explain the observed irregularities in experimental results.We studied the natural variability effect as well and proposed a methodology to overcome the issue of specimen representativity from both deviatoric and volumetric perspectives.展开更多
A hybrid Cellular Automaton(CA)-Parabolic Thick Needle(PTN)model is developed for the simulation of an equiaxed dendritic grain.It is implemented by solving conservation equations with the Finite Element(FE)method at ...A hybrid Cellular Automaton(CA)-Parabolic Thick Needle(PTN)model is developed for the simulation of an equiaxed dendritic grain.It is implemented by solving conservation equations with the Finite Element(FE)method at two scales.At the scale of the microstructure,dendritic branches are approximated by a network of PTN.The solute field is computed in the liquid using a FE mesh with minimum size smaller than the diffusion length ahead of the dendrite tips,giving access to a detailed description of each dendrite tip growth velocity as well as solutal interactions between branches.At the simulation domain scale,volume averaged heat and solute transfers are solved on a coarser FE mesh.The average volumetric fraction of phases is deduced from a field giving the fraction of dendritic microstructure together with a microsegregation model.Because the PTN themselves grow on CA cells,the dendrite tip growth velocity is transferred to the vertices of the polygon associated to the CA growth shape.Similarly,the field giving the fraction of dendritic microstructure is deduced from the fraction of CA cells part of the mushy zone,which include cells containing PTN network.Advantages of the new multiple scale CAPTN model include solutal interaction between dendrite branches together with long range transfer of heat and solute mass,together with the role of latent heat release on equiaxed solidification.展开更多
Process scale-up remains a considerable challenge for environmental applications of non-thermal plasmas.Undersanding the impact of reactor hydrodynamics in the performance of the process is a key step to overcome this...Process scale-up remains a considerable challenge for environmental applications of non-thermal plasmas.Undersanding the impact of reactor hydrodynamics in the performance of the process is a key step to overcome this challenge.In this work,we apply chemical engineering concepts to analyse the impact that different non-thermal plasma reactor configurations and regimes,such as laminar or plug flow,may have on the reactor performance.We do this in the particular context of the removal of pollutants by non-thermal plasmas,for which a simplified model is available.We generalise this model to different reactor configurations and,under certain hypotheses,we show that a reactor in the laminar regime may have a behaviour significantly different from one in the plug flow regime,often assumed in the non-thermal plasma literature.On the other hand,we show that a packed-bed reactor behaves very similarly to one in the plug flow regime.Beyond those results,the reader will find in this work a quick introduction to chemical reaction engineering concepts.展开更多
Numerical modeling of thermally-induced fractures is a concern for many geo-structures including deep underground energy storage caverns. In this paper, we present the numerical simulation of a large-scale cooling exp...Numerical modeling of thermally-induced fractures is a concern for many geo-structures including deep underground energy storage caverns. In this paper, we present the numerical simulation of a large-scale cooling experiment performed in an underground rock salt mine. The theory of fracture mechanics was embedded in the extended finite element code used. The results provide reliable information on fracture location and fracture geometry. Moreover, the timing of the fracture onset, as well as the stress redis- tribution due to fracture propagation, is highlighted. The conclusions of this numerical approach can be used to improve the design of rock salt caverns in order to guarantee their integrity in terms of both their tightness and stability.展开更多
The flow regimes of GLCC with horizon inlet and a vertical pipe are investigated in experiments,and the velocities and pressure drops data labeled by the corresponding flow regimes are collected.Combined with the flow...The flow regimes of GLCC with horizon inlet and a vertical pipe are investigated in experiments,and the velocities and pressure drops data labeled by the corresponding flow regimes are collected.Combined with the flow regimes data of other GLCC positions from other literatures in existence,the gas and liquid superficial velocities and pressure drops are used as the input of the machine learning algorithms respectively which are applied to identify the flow regimes.The choosing of input data types takes the availability of data for practical industry fields into consideration,and the twelve machine learning algorithms are chosen from the classical and popular algorithms in the area of classification,including the typical ensemble models,SVM,KNN,Bayesian Model and MLP.The results of flow regimes identification show that gas and liquid superficial velocities are the ideal type of input data for the flow regimes identification by machine learning.Most of the ensemble models can identify the flow regimes of GLCC by gas and liquid velocities with the accuracy of 0.99 and more.For the pressure drops as the input of each algorithm,it is not the suitable as gas and liquid velocities,and only XGBoost and Bagging Tree can identify the GLCC flow regimes accurately.The success and confusion of each algorithm are analyzed and explained based on the experimental phenomena of flow regimes evolution processes,the flow regimes map,and the principles of algorithms.The applicability and feasibility of each algorithm according to different types of data for GLCC flow regimes identification are proposed.展开更多
A comparative study related to the preparation of poly(2-hydroxyethyl methacrylate) (pHEMA) through radical polymerization process in the presence of three different protective colloid substances, respectively poly(vi...A comparative study related to the preparation of poly(2-hydroxyethyl methacrylate) (pHEMA) through radical polymerization process in the presence of three different protective colloid substances, respectively poly(vinyl alcohol) (PVA), β-cyclodextrin, or poly(aspartic acid) (PAS), is presented. The dependence of the thermal behavior of the polymers as well as their morphological aspect, on the protective colloids used in synthesis was evidenced by polymers characterization. It is also demonstrated that the swelling capacity is dependent on the protective colloid variant present during the pHEMA preparation. This behavior induces as well interdependence on the ability to load bioactive compounds onto the polymeric matrices. The distribution of the indomethacin (INN), as model drug, into the pHEMA network was put into evidence by near infrared chemical imaging (NIR-CI), a non-destructive technique and with its correspondingly statistical analysis.展开更多
This paper presents the STAMP （system-theoretic accident modeling and processes） accident model, based on systems theory, and describes its application in the context of risk prevention related to the remediation of...This paper presents the STAMP （system-theoretic accident modeling and processes） accident model, based on systems theory, and describes its application in the context of risk prevention related to the remediation of contaminated sediments. The implementation of the model is described, and results are presented both in methodological and technical terms. The goal of this article is to emphasize the need of new approaches to take into account hazards and accidents within socio-technical systems.展开更多
The propagation of small cracks contributes to the majority of the fatigue lifetime for structural components.Despite significant interest,criteria for the growth of small cracks,in terms of the direction and speed of...The propagation of small cracks contributes to the majority of the fatigue lifetime for structural components.Despite significant interest,criteria for the growth of small cracks,in terms of the direction and speed of crack advancement,have not yet been determined.In this work,a new approach to identify the microstructurally small fatigue crack driving force is presented.Bayesian network and machine learning techniques are utilized to identify relevant micromechanical and microstructural variables that influence the direction and rate of the fatigue crack propagation.A multimodal dataset,combining results from a high-resolution 4D experiment of a small crack propagating in situ within a polycrystalline aggregate and crystal plasticity simulations,is used to provide training data.The relevant variables form the basis for analytical expressions thus representing the small crack driving force in terms of a direction and a rate equation.The ability of the proposed expressions to capture the observed experimental behavior is quantified and compared to the results directly from the Bayesian network and from fatigue metrics that are common in the literature.Results indicate that the direction of small crack propagation can be reliably predicted using the proposed analytical model and compares more favorably than other fatigue metrics.展开更多
Most current crowdsourced logistics aim to minimize systems cost and maximize delivery capacity,but the efforts of crowdsourcers such as drivers are almost ignored.In the delivery process,drivers usually need to take ...Most current crowdsourced logistics aim to minimize systems cost and maximize delivery capacity,but the efforts of crowdsourcers such as drivers are almost ignored.In the delivery process,drivers usually need to take long-distance detours in hitchhiking rides based package deliveries.In this paper,we propose an approach that integrates offline trajectory data mining and online route-and-schedule optimization in the hitchhiking ride scenario to find optimal delivery routes for packages and drivers.Specifically,we propose a two-phase framework for the delivery route planning and scheduling.In the first phase,the historical trajectory data are mined offline to build the package transport network.In the second phase,we model the delivery route planning and package-taxi matching as an integer linear programming problem and solve it with the Gurobi optimizer.After that,taxis are scheduled to deliver packages with optimal delivery paths via a newly designed scheduling strategy.We evaluate our approach with the realworld datasets;the results show that our proposed approach can complete citywide package deliveries with a high success rate and low extra efforts of taxi drivers.展开更多
基金supported by the European Research Fund for Coal and Steel in the AMSSTED Programme RFCR-CT-2013-00001
文摘Laboratory pull-out tests were conducted on the following rock bolts and cable bolts:steel rebars,smooth steel bars,fiberglass reinforced polymer threaded bolts,flexible cable bolts,IR5/IN special cable bolts and Mini-cage cable bolts.The diameter of the tested bolts was between 16 mm and 26 mm.The bolts were grouted in a sandstone sample using resin or cement grouts.The tests were conducted under either constant radial stiffness or constant confining pressure boundary conditions applied on the outer surface of the rock sample.In most tests,the rate of displacement was about 0.02 mm/s.The tests were performed using a pull-out bench that allows testing a wide range of parameters.This paper provides an extensive database of laboratory pull-out test results and confirms the influence of the confining pressure and the embedment length on the pull-out response(rock bolts and cable bolts).It also highlights the sensitivity of the results to the operating conditions and to the behavior of the sample as a whole,which cannot be neglected when the test results are used to assess the bolt-grout or the grouterock interface.
基金supported by the National Science Foundation grant CMMI-1405508
文摘A major dilemma faced in the nuclear industry is repair of stainless steel reactor components that have been exposed to neutron irradiation. When conventional fusion welding is used for repair, intergranular cracks develop in the heat-affected zone(HAZ). Friction stir processing(FSP), which operates at much lower peak temperatures than fusion welding, was studied as a crack repair method for irradiated 304 L stainless steel. A numerical simulation of the FSP process in 304 L was developed to predict temperatures and recrystallized grain size in the stir zone. The model employed an Eulerian finite element approach,where flow stresses for a large range of strain rates and temperatures inherent in FSP were used as input. Temperature predictions in three locations near the stir zone were accurate to within 4%, while prediction of welding power was accurate to within 5% of experimental measurements. The predicted recrystallized grain sizes ranged from 7.6 to 10.6 μm, while the experimentally measured grains sizes in the same locations ranged from 6.0 to 7.6 μm. The maximum error in predicted recrystallized grain size was about 39%, but the associated stir zone hardness from the predicted grain sizes was only different from the experiment by about 10%.
文摘Charnockites sensu lato （charnockite-enderbite series） are lower crustal felsic rocks typically characterised by the presence of anhydrous minerals including orthopyroxene and garnet. They either represent dry （H2O-poor） felsic magmas that are emplaced in the lower crust or granitic intrusions that have been dehydrated during a subsequent granulite facies metamorphic event. In the first case, post- magmatic high-temperature recrystallisation may result in widespread metamorphic granulite microstruc- tures, superimposed or replacing the magmatic microstructures. Despite recrystallisation, magmatic remnants may still be found, notably in the form of melt-related microstructures such as melt inclusions. For both magmatic charnockites and dehydrated granites, subsequent fluid-mineral interaction at inter- grain boundaries during retrogradation are documented by microstructures including K-feldspar micro- veins and myrmekites. They indicate that a large quantity of low-H2O activity salt-rich brines, were present （together with CO2 under immiscible conditions） in the lower crust.
基金supported by the Research Fund for Coal and Steel(RFCS)in the context of the European project Advancing Mining Support Systems to Enhance the Control of Highly Stressed Ground(AMSSTED)。
文摘This paper proposes a new interface constitutive model for fully grouted rock-bolts and cable-bolts based on pull-out test results.A database was created combining published experimental data with in-house tests.By means of a comprehensive framework,a Coulomb-type failure criterion accounting for friction mobilization was defined.During the elastic phase,in which the interface joint is not yet created,the proposed model provides zero radial displacement,and once the interface joint is created,interface dilatancy is modeled using a non-associated plastic potential inspired from the behavior of rock joints.The results predicted by the proposed model are in good agreement with experimental results.The model has been implemented in a finite element method(FEM)code and numerical simulations have been performed at the elementary and the structural scales.The results obtained provide confidence in the ability of the new model to assist in the design and optimization of bolting patterns.
基金supported by the National Key Research and Development Plan of China(No.2019YFB1706001)the National Natural Science Foundation of China(No.61773001)。
文摘The article focuses on the design and application of an active reconfigurable controller that mitigates the effects of gust load and actuator faults on a flexible aircraft.A novel integrated adaptive output feedback scheme is investigated to address the actuator faults.The real-time fault values provided by the fault estimation module are considered in the reconfigurable control law to improve the fault-tolerant capability.The estimate values of faults and control gains are calculated by analyzing the stability of the overall system.The proposed controller is simulated using a flexible aircraft model with a discrete‘1-cosine’gust,and the results show that it can effectively mitigate the wing root moments and recover the flight maneuver stability after the aircraft suffered from gusts.
基金supported by National Natural Science Foundation of China[grant number 51904316]provided by China University of Petroleum,Beijing[grant number2462021YJRC013,2462020YXZZ045]
文摘An integrated dynamic model of natural gas pipeline networks is developed in this paper.Components for gas supply,e.g.,pipelines,junctions,compressor stations,LNG terminals,regulation stations and gas storage facilities are included in the model.These components are firstly modeled with respect to their properties and functions and,then,integrated at the system level by Graph Theory.The model can be used for simulating the system response in different scenarios of operation,and evaluate the consequences from the perspectives of supply security and resilience.A case study is considered to evaluate the accuracy of the model by benchmarking its results against those from literature and the software Pipeline Studio.Finally,the model is applied on a relatively complex natural gas pipeline network and the results are analyzed in detail from the supply security and resilience points of view.The main contributions of the paper are:firstly,a novel model of a complex gas pipeline network is proposed as a dynamic state-space model at system level;a method,based on the dynamic model,is proposed to analyze the security and resilience of supply from a system perspective.
文摘Recently,stress-based dilatancy criteria have become essential tools to design underground facilities in salt formations such as gas storage caverns.However,these criteria can depend critically on the volumetric strain measurements used to deduce the dilatancy onset.Results from conventional triaxial compression tests can show different volumetric behavior depending on the loading conditions,as well as on the measurement techniques.In order to obtain a quantitative understanding of this problem,an experimental program was carried out and the testing procedure was investigated numerically under homogeneous and heterogeneous stress states.The experimental results showed that the deviatoric stress corresponding to the dilatancy onset was significantly dependent on the measurement techniques.With a heterogeneous stress state,the simulation results revealed that the strain measurements at different scales (referred to as local,hybrid or global) can provide different volumetric results with moderate to significant deviations from the idealized behavior,and hence different onsets of dilatancy.They also proved that,under low confinement,tensile stresses can take place within the compressed specimen,leading to a great deviation of the dilatancy onset from the idealized behavior.From both experimental and numerical investigations,the difference in sensitivity to the measurement techniques between the deviatoric and the volumetric behaviors is explained by the relatively small values of the volumetric strain.The non-ideal laboratory conditions have more impact on this strain than on the deviatoric one.These findings can have implications for the interpretation of the dilatancy behavior of rock salt,and hence on the geomechanical design aspects in salt formations.
基金co-supported by the National Natural Science Foundation of China(Nos.51875014,51575019,51620105010)Natural Science Foundation of Beijing Municipality(No.L171003)Program 111 of China。
文摘The degradation of components in complex mechatronic systems involves multiple physical processes which will cause coupling interactions among nodes in the system.The interaction of nodes may be carried out not only by physical connections but also by the environment which cannot be described by single network using the traditional methods.In order to give out a unified model to quantitatively describe the coupling degradation spreading by both physical connections and environment,a novel Energy-Flow-Field Network(EFFN)and a coupling degradation model based on EFFN are proposed in this paper.The EFFN is driven by energy flow and the state transition of spatially related nodes is triggered by the dissipation energy.An application is conducted on aviation actuation system in which the degradation spreading by fluid-thermal-solid interaction is considered.The degradation path and the most probable fault reason can be obtained by combining the state transition and energy output of nodes,which is consistent with the given scenario.
文摘This paper investigates the electrical and mechanical behaviors of a single-ASDBD actuator and a two-ASDBD one supplied in sinusoidal mode（1-10 kHz）.The main objective of our research is to determine the optimum frequency values for the function of these actuators with a given power supply.For this purpose,we determine the electrical power density input to the actuators versus frequency through two methods：i） a semi-theoretical method,based on an impedance calculation,and ii） an experimental method,based on direct electrical measurements.These methods show that the addition of a second ASDBD changes the resonance frequency value of the actuator by moving it towards low frequencies.After characterizing the aerodynamic mobile layer structure induced by the single-ASDBD actuator,we analyze experimentally the mechanical response of a two-ASDBD actuator as a function of the inter-ASDBD distance.The experiments demonstrate that the induced electric wind velocity and the electro-mechanical yield of a twoASDBD actuator reach a maximum value for an optimum inter-ASDBD distance,which is a useful value for the design of highly efficient multi-ASDBD actuators.
文摘The goal of this article is dual： first, introducing a new model of accident named STAMP （systems-theoretic accident modeling and processes）; then applying the model to an innovative process for the treatment of contaminated substances and the re-use of treated substances. This article is a demonstration for a need of a new tool to take into account hazards and safety within socio-technical systems.
基金Dr. F.Latourte (EDF Research and Development Division,Les Renardières,Moret-sur-Loing,France) and Dr. J.M.Proix (EDF Research and Development Division,Clamart,France),and the MAI-SN (EDF,Les Renardières,Moret-sur-Loing,France) for stimulating discussions and financial support for part of this study
文摘The dislocation density tensor computed as the cud of plastic distortion is regarded as a new constitutive variable in crystal plasticity. The dependence of the free energy function on the dislocation density tensor is explored starting from a quadratic ansatz. Rank one and logarithmic dependencies are then envisaged based on considerations from the statistical theory of dislocations. The rele- vance of the presented free energy potentials is evaluated from the corresponding analytical solutions of the periodic two-phase laminate problem under shear where one layer is a single crystal material undergoing single slip and the second one remains purely elastic.
文摘This paper focuses on the presence of nodules of insoluble materials within salt specimens,and their effect on the volumetric strain measurements and the dilatancy phenomenon.We analyzed experimental results of over 120 conventional triaxial compression tests,and found that in 20%of the cases,the volumetric strain measurements were atypical.We also noted that the natural variability of the specimens can lead to a non-negligible data scattering in the volumetric strain measurements when different specimens are subjected to the same test.This is expected given the small magnitude of those strains,but it occasionally implies that the corresponding specimens are not representative of the volumetric behavior of the studied rock.In order to understand these results,we numerically investigated salt specimens modeled as halite matrices with inclusions of impurities.Simulations of triaxial compression tests on these structures proved that such heterogeneities can induce dilatancy,and their presence can lead to the appearance of tensile zones which is physically translated into a micro-cracking activity.The modeling approach is validated as the patterns displayed in the numerical results are identical to that in the laboratory.It was then employed to explain the observed irregularities in experimental results.We studied the natural variability effect as well and proposed a methodology to overcome the issue of specimen representativity from both deviatoric and volumetric perspectives.
基金conducted within the ESA-MAP program‘CETSOL’contract 14313/01/NL/SH
文摘A hybrid Cellular Automaton(CA)-Parabolic Thick Needle(PTN)model is developed for the simulation of an equiaxed dendritic grain.It is implemented by solving conservation equations with the Finite Element(FE)method at two scales.At the scale of the microstructure,dendritic branches are approximated by a network of PTN.The solute field is computed in the liquid using a FE mesh with minimum size smaller than the diffusion length ahead of the dendrite tips,giving access to a detailed description of each dendrite tip growth velocity as well as solutal interactions between branches.At the simulation domain scale,volume averaged heat and solute transfers are solved on a coarser FE mesh.The average volumetric fraction of phases is deduced from a field giving the fraction of dendritic microstructure together with a microsegregation model.Because the PTN themselves grow on CA cells,the dendrite tip growth velocity is transferred to the vertices of the polygon associated to the CA growth shape.Similarly,the field giving the fraction of dendritic microstructure is deduced from the fraction of CA cells part of the mushy zone,which include cells containing PTN network.Advantages of the new multiple scale CAPTN model include solutal interaction between dendrite branches together with long range transfer of heat and solute mass,together with the role of latent heat release on equiaxed solidification.
文摘Process scale-up remains a considerable challenge for environmental applications of non-thermal plasmas.Undersanding the impact of reactor hydrodynamics in the performance of the process is a key step to overcome this challenge.In this work,we apply chemical engineering concepts to analyse the impact that different non-thermal plasma reactor configurations and regimes,such as laminar or plug flow,may have on the reactor performance.We do this in the particular context of the removal of pollutants by non-thermal plasmas,for which a simplified model is available.We generalise this model to different reactor configurations and,under certain hypotheses,we show that a reactor in the laminar regime may have a behaviour significantly different from one in the plug flow regime,often assumed in the non-thermal plasma literature.On the other hand,we show that a packed-bed reactor behaves very similarly to one in the plug flow regime.Beyond those results,the reader will find in this work a quick introduction to chemical reaction engineering concepts.
文摘Numerical modeling of thermally-induced fractures is a concern for many geo-structures including deep underground energy storage caverns. In this paper, we present the numerical simulation of a large-scale cooling experiment performed in an underground rock salt mine. The theory of fracture mechanics was embedded in the extended finite element code used. The results provide reliable information on fracture location and fracture geometry. Moreover, the timing of the fracture onset, as well as the stress redis- tribution due to fracture propagation, is highlighted. The conclusions of this numerical approach can be used to improve the design of rock salt caverns in order to guarantee their integrity in terms of both their tightness and stability.
文摘The flow regimes of GLCC with horizon inlet and a vertical pipe are investigated in experiments,and the velocities and pressure drops data labeled by the corresponding flow regimes are collected.Combined with the flow regimes data of other GLCC positions from other literatures in existence,the gas and liquid superficial velocities and pressure drops are used as the input of the machine learning algorithms respectively which are applied to identify the flow regimes.The choosing of input data types takes the availability of data for practical industry fields into consideration,and the twelve machine learning algorithms are chosen from the classical and popular algorithms in the area of classification,including the typical ensemble models,SVM,KNN,Bayesian Model and MLP.The results of flow regimes identification show that gas and liquid superficial velocities are the ideal type of input data for the flow regimes identification by machine learning.Most of the ensemble models can identify the flow regimes of GLCC by gas and liquid velocities with the accuracy of 0.99 and more.For the pressure drops as the input of each algorithm,it is not the suitable as gas and liquid velocities,and only XGBoost and Bagging Tree can identify the GLCC flow regimes accurately.The success and confusion of each algorithm are analyzed and explained based on the experimental phenomena of flow regimes evolution processes,the flow regimes map,and the principles of algorithms.The applicability and feasibility of each algorithm according to different types of data for GLCC flow regimes identification are proposed.
文摘A comparative study related to the preparation of poly(2-hydroxyethyl methacrylate) (pHEMA) through radical polymerization process in the presence of three different protective colloid substances, respectively poly(vinyl alcohol) (PVA), β-cyclodextrin, or poly(aspartic acid) (PAS), is presented. The dependence of the thermal behavior of the polymers as well as their morphological aspect, on the protective colloids used in synthesis was evidenced by polymers characterization. It is also demonstrated that the swelling capacity is dependent on the protective colloid variant present during the pHEMA preparation. This behavior induces as well interdependence on the ability to load bioactive compounds onto the polymeric matrices. The distribution of the indomethacin (INN), as model drug, into the pHEMA network was put into evidence by near infrared chemical imaging (NIR-CI), a non-destructive technique and with its correspondingly statistical analysis.
文摘This paper presents the STAMP （system-theoretic accident modeling and processes） accident model, based on systems theory, and describes its application in the context of risk prevention related to the remediation of contaminated sediments. The implementation of the model is described, and results are presented both in methodological and technical terms. The goal of this article is to emphasize the need of new approaches to take into account hazards and accidents within socio-technical systems.
基金M.D.S.and A.R.gratefully acknowledge support from the Air Force Office of Scientific Research under Contract No.FA9550-14-1-0284.
文摘The propagation of small cracks contributes to the majority of the fatigue lifetime for structural components.Despite significant interest,criteria for the growth of small cracks,in terms of the direction and speed of crack advancement,have not yet been determined.In this work,a new approach to identify the microstructurally small fatigue crack driving force is presented.Bayesian network and machine learning techniques are utilized to identify relevant micromechanical and microstructural variables that influence the direction and rate of the fatigue crack propagation.A multimodal dataset,combining results from a high-resolution 4D experiment of a small crack propagating in situ within a polycrystalline aggregate and crystal plasticity simulations,is used to provide training data.The relevant variables form the basis for analytical expressions thus representing the small crack driving force in terms of a direction and a rate equation.The ability of the proposed expressions to capture the observed experimental behavior is quantified and compared to the results directly from the Bayesian network and from fatigue metrics that are common in the literature.Results indicate that the direction of small crack propagation can be reliably predicted using the proposed analytical model and compares more favorably than other fatigue metrics.
基金This work was supported in part by the National Natural Science Foundation of China(Grant No.61872050)in part by the Chongqing Basic and Frontier Research Program(cstc2018jcyjAX0551)+2 种基金Foundation of Chongqing Municipal Key Laboratory of Institutions of Higher Education([2017]3)Foundation of Chongqing Development and Reform Commission(2017[1007])Foundation of Chongqing Three Gorges University.Sijing Cheng and Chao Chen contributed equally to this work.Wei Zhang is the corresponding authors for this paper.
文摘Most current crowdsourced logistics aim to minimize systems cost and maximize delivery capacity,but the efforts of crowdsourcers such as drivers are almost ignored.In the delivery process,drivers usually need to take long-distance detours in hitchhiking rides based package deliveries.In this paper,we propose an approach that integrates offline trajectory data mining and online route-and-schedule optimization in the hitchhiking ride scenario to find optimal delivery routes for packages and drivers.Specifically,we propose a two-phase framework for the delivery route planning and scheduling.In the first phase,the historical trajectory data are mined offline to build the package transport network.In the second phase,we model the delivery route planning and package-taxi matching as an integer linear programming problem and solve it with the Gurobi optimizer.After that,taxis are scheduled to deliver packages with optimal delivery paths via a newly designed scheduling strategy.We evaluate our approach with the realworld datasets;the results show that our proposed approach can complete citywide package deliveries with a high success rate and low extra efforts of taxi drivers.
