Eleven evaluating parameters for rice core collection were assessed based on genotypic values and molecular marke＇ information. Monte Carlo simulation combined with mixed linear model was used to eliminate the interf...Eleven evaluating parameters for rice core collection were assessed based on genotypic values and molecular marke＇ information. Monte Carlo simulation combined with mixed linear model was used to eliminate the interference from environment in order to draw more reliable results. The coincidence rate of range （CR） was the optimal parameter. Mean Simpson index （MD）, mean Shannon-Weaver index of genetic diversity （M1） and mean polymorphism information content （MPIC） were important evaluating parameters. The variable rate of coefficient of variation （VR） could act as an important reference parameter for evaluating the variation degree of core collection. Percentage of polymorphic loci （p） could be used as a determination parameter for the size of core collection. Mean difference percentage （MD） was a determination parameter for the reliability judgment of core collection. The effective evaluating parameters for core collection selected in the research could be used as criteria for sampling percentage in different plant germplasm populations.展开更多
The threshold stress, σc, for sulfide stress corrosion cracking (SCC) of seven pipeline steels and five other steels, the critical stress, Sc, for seven pipeline steels and two drill rod steels with various strengths...The threshold stress, σc, for sulfide stress corrosion cracking (SCC) of seven pipeline steels and five other steels, the critical stress, Sc, for seven pipeline steels and two drill rod steels with various strengths and the susceptibility to SCC, IRA or σf(SCC)/σf, for four pipeline steels, two drill rod steels and five other steels were measured. The results showed that there are no definite relationships among σc, Sc and IRA or σf(SCC)/σf.The threshold stress for hydrogen induced cracking (HlC) during charging with loading in the H2S04 solution, σc(H), decreased linearly with logarithm of the concentration of diffusible hydrogen c0, i.e., σc(H)=A-B Inco for four pipeline steels. σc(H) obtained with a special cathodic current ic, which was corresponding to the diffusible hydrogen concentration during immersing in the H2S solution, were consistent with /c for sulfide SCC for four pipeline steels. Therefore, σc for sulfide SCC can be measured using dynamically charging in the H2SO4 solution with the special cathodic current ic.展开更多
Parameter inversions in oil/gas reservoirs based on well test interpretations are of great significance in oil/gas industry.Automatic well test interpretations based on artificial intelligence are the most promising t...Parameter inversions in oil/gas reservoirs based on well test interpretations are of great significance in oil/gas industry.Automatic well test interpretations based on artificial intelligence are the most promising to solve the problem of non-unique solution.In this work,a new deep reinforcement learning(DRL)based approach is proposed for automatic curve matching for well test interpretation,by using the double deep Q-network(DDQN).The DDQN algorithms are applied to train agents for automatic parameter tuning in three conventional well-testing models.In addition,to alleviate the dimensional disaster problem of parameter space,an asynchronous parameter adjustment strategy is used to train the agent.Finally,field applications are carried out by using the new DRL approaches.Results show that step number required for the DDQN to complete the curve matching is the least among,when comparing the naive deep Q-network(naive DQN)and deep Q-network(DQN).We also show that DDQN can improve the robustness of curve matching in comparison with supervised machine learning algorithms.Using DDQN algorithm to perform 100 curve matching tests on three traditional well test models,the results show that the mean relative error of the parameters is 7.58%for the homogeneous model,10.66%for the radial composite model,and 12.79%for the dual porosity model.In the actual field application,it is found that a good curve fitting can be obtained with only 30 steps of parameter adjustment.展开更多
An efficient procedure is used for explicit description and evaluation of uncertainty of earthquake parameters in the uniform catalog of earthquakes in Iran and neighboring regions.An inadequate number of local and re...An efficient procedure is used for explicit description and evaluation of uncertainty of earthquake parameters in the uniform catalog of earthquakes in Iran and neighboring regions.An inadequate number of local and regional seismographic stations,poor station distribution,and Inadequacy of velocity models have resulted in conspicuous uncertainty in different parameters of recorded events.In a comprehensive seismic hazard analysis such uncertainties should be considered.Uncertainty of magnitude and location of events are evaluated for three different time periods,namely,historical,early instrumental,and modern instrumental time periods,for which existing seismological information differ widely in quantity,quality,and type.It is concluded that an uncertainty of 0.2-0.3 units of magnitude and 10-15 km in epicenter determinations should be considered in the most favorable conditions.None of the hypocenters of earthquakes in Iran can be considered as reliable,unless supported by other information such as展开更多
In order to investigate the corrosion mechanism of recycled reinforced concrete (RRC) under harsh environments,four recycled coarse aggregate (RCA) contents were selected,and saline soil was used as an electrolyte to ...In order to investigate the corrosion mechanism of recycled reinforced concrete (RRC) under harsh environments,four recycled coarse aggregate (RCA) contents were selected,and saline soil was used as an electrolyte to perform electrified accelerated corrosion experiments.The relative dynamic elastic modulus and relative corrosion current density were considered to describe the deterioration law of the RRC in saline soil.The results indicated that as the energization time increased,the corrosion current density,corrosion potential,and polarization resistance of the steel bar decreased gradually.Compared with ordinary reinforced concrete,when the RCA content was 30%,the ability of the RRC to resist corrosion was improved slightly;however,when the RCA content exceeded 30%,the corrosion resistance of the RRC deteriorated rapidly.Scanning electron microscopy revealed that for a dense RRC,less corrosion products were generated in the pores inside the concrete and on the surface of the steel bar.X-ray diffraction results indicated that SO_(4)^(2-) can generate ettringite and other corrosion products,along with volume expansion.The main corrosion products generated on the surface of the steel bars included Fe_(2)O_(3),Fe_(3)O_(4) and FeO(OH),which were the corrosion products generated by steel bars under natural environments.Therefore,using saline soil as an electrolyte is more consistent with the actual service environments of RRC.Both the relative dynamic mode and relative corrosion current density of the degradation parameters conform to the Weibull distribution;furthermore,the relative dynamic mode is more sensitive and the corresponding reliability curve can better describe the degradation law of RRC under saline soil environments.展开更多
In order to obtain effective parameters for complex sand reservoirs,a log evaluation method for relevant reservoir parameters is established based on an analysis in the gas-bearing sandstone with high porosity and low...In order to obtain effective parameters for complex sand reservoirs,a log evaluation method for relevant reservoir parameters is established based on an analysis in the gas-bearing sandstone with high porosity and low permeability,low porosity and permeability and on various characteristics of log responses to reservoir lithologies and physical properties in the Neopleozoic sand reservoir of the Ordos basin.This log evaluation method covers the Cook method that is used to evaluate the porosity and oiliness in high porosity and low permeability reservoirs and another method in which the mineral content,derived from geochemical logs,is used to identify formation lithologies.Some areas have high calcium and low silt content,not uniformly distributed,the results of which show up in the complex formation lithologies and conventional log responses with great deviation.The reliability of the method is verified by comparison with conventional log data and core analyses.The calculation results coincide with the core analytical data and gas tests,which indicate that this log evaluation method is available,provides novel ideas for study of similar complex reservoir lithologies and has some reference value.展开更多
Asphalt mixtures exhibit strong viscous properties under repetitive loads. This phenomenon can be simulated in creep and recovery tests. By applying the visco elastoplastic model proposed, data recorded in the tests ...Asphalt mixtures exhibit strong viscous properties under repetitive loads. This phenomenon can be simulated in creep and recovery tests. By applying the visco elastoplastic model proposed, data recorded in the tests are interpreted. It is emphasised that applicability of the visco elastoplastic model depends on the proper method of characterising parameters involved in the constitutive equations. Since two or more strain components of elasticity and viscosity coexist during the loading or unloading, a measuring system of two loggers is introduced to decouple these components. Test data are analysed in three steps as elastic, visco elastic and visco plastic evaluations, using the records collected at the moment of unloading, during the periods of recovery and creep respectively. Factors that may influence the accuracy of data analysis are also discussed.展开更多
This paper developed an improved combinatorial method called the best chromosome clone plus younger generation chromosome prepotency genetic algorithm （BCC-YGCP-GA） to evaluate aquifer parameters. This method is bas...This paper developed an improved combinatorial method called the best chromosome clone plus younger generation chromosome prepotency genetic algorithm （BCC-YGCP-GA） to evaluate aquifer parameters. This method is based on a decimal simple genetic algorithm （SGA）. A synthetic example for unsteady-state flow in a two-dimensional, inhomogeneous, confined aquifer containing three hydraulically distinct zones, is used to develop data to test the model. The simulation utilizes SGA and BCC-YGCP-GA coupled to the finite element method to identify the mean zonal hydraulic conductivities, and storage coefficients of the three-compartment model. For this geometrically simple model, used as a prototype of more complex systems, the SGA does not reach convergence within 100 generations. Conversely, the convergence rate of the BCC-YGCD-GA model is very fast. The objective function value calculated by BCC-YGCD-GA is reduced to 1/1 O00th of the starting value within 100 generations, and the hydraulic conductivity and storage of three zones are within a few percent of the “true” values of the ideal model, highlighting the power of the method for aquifer parameterization.展开更多
For the purpose of enhancing automobile safety and the effectiveness of recalls,increasing manufacturers' quality control capabilities,and reducing defects,we investigated thestatus of recalls over the last five y...For the purpose of enhancing automobile safety and the effectiveness of recalls,increasing manufacturers' quality control capabilities,and reducing defects,we investigated thestatus of recalls over the last five years.We have examined patterns and trends in motor vehiclesafety recalls using databases from China,Europe and the United States.A recall rate parameterwas developed to evaluate the level of recall enforcement based on analyzing the reasonsfor recalls and manufactures' characteristics.Moreover,there were substantial differencesin the recall rates of China compared with those in other countries,indicating that Chinese manufacturersneed to take more active action in recall.展开更多
Finite supply of non-regenerative resources triggers a competition between economic entities or between areas, which requires the ways regarding their utilization with higher levels in science and the standards regard...Finite supply of non-regenerative resources triggers a competition between economic entities or between areas, which requires the ways regarding their utilization with higher levels in science and the standards regarding their use with higher efficiency in economics. To solve a problem of process evaluation in science and of driving force in economics during a process design or a process run for natural resources utilization, a process evaluation parameter originated from natural gas hydrate preparation from a small scale to industrialization scale and the equation of the criterion dependent are introduced to evaluate a variety of processes of natural resources utilization. The analyses indicate that the parameter is relevant to internal undeveloped resources amount change with a stable mass composition in a virtual black box model and external variable market with an implication of process efficiency in economy or of process efficiency of resource utilization and that the parameter has similar features of the thermodynamic state functions. Moreover, the equation of the criterion provided is a difference between the value of the process evaluation parameter at the final state and the value of the process evaluation parameter at the initial state in an actual process, which can be used to determine the direction of development and to judge the size of the driving force in an actual process or an economical run. The provided examples and correlative mathematical description can guide how an identification for the undeveloped resources and a real-time adjustment of dynamic production for the developing resource are done and how decisions regarding resource exploitation, the venture forecasting of capital utilization and updating technology are made. The parameter used itself and the equation of the derived criterion can help by playing a predictive role for selecting the optimal use processes and for designing new process of the natural resource utilization or capital use, and by playing a practical role for adjusting factual production status and for improving the actual process of the utilization of resource or capital in an economic society. Finally, those closed resource systems having accumulation or depletion of the resources or a variable mass such as a decomposition system, a fission system and a biological reproduction system will become possible future research objectives under the guide of this work.展开更多
Corner stall receives noticeable attention in the aeroengine field as an important phenomenon in highly-load compressors.Non-uniform leading-edge tubercles,as an effective method to delay stall,are introduced into the...Corner stall receives noticeable attention in the aeroengine field as an important phenomenon in highly-load compressors.Non-uniform leading-edge tubercles,as an effective method to delay stall,are introduced into the compressor.In this paper,the shape of leading-edge tubercles was controlled by a third-order Fourier function.To judge corner stall,a more precise stall indicator for compressor cascade with flow control methods was defined.Besides,the total kinetic energy of the secondary flow at large incidence was adopted as a parameter for stall evaluation to save computing resources.The results of multiobjective optimization reveal that the loss coefficient exhibited negligible variation at design incidence,while the total kinetic energy of secondary flow showed a significant reduction at large incidence,resulting in a substantial increase in stall incidence.In the optimal profiling cases,the stall incidencewas delayed from 7.9°to 11.6°.The major purpose of the research is to provide proper design guidelines for nonuniformleading-edge tubercles and uncover the flow controlmechanisms of leading-edge profiling.Hence,the geometric features that meet different optimization objectives were extracted through geometric analysis near the Pareto Front and through Self-OrganizingMap(SOM)dataminingmethods in the optimization database.Besides,flow field analysis reveals the flow control mechanism of leading-edge tubercles.The convex-concave-convex structure at the 0%-70%blade height region can form two branches of leading-edge vortex pairs that are opposite in the rotation direction to the passage vortex.The two branches of leading-edge vortex pairs mixed with the leading-edge separation vortex to form two stronger mixed vortices,which can effectively suppress the development of passage vortex and delay stall incidence.展开更多
relationships between logging data and reservoir parameters.We compare our method’s performances using two datasets and evaluate the influences of multi-task learning,model structure,transfer learning,and petrophysic...relationships between logging data and reservoir parameters.We compare our method’s performances using two datasets and evaluate the influences of multi-task learning,model structure,transfer learning,and petrophysics informed machine learning(PIML).Our experiments demonstrate that PIML significantly enhances the performance of formation evaluation,and the structure of residual neural network is optimal for incorporating petrophysical constraints.Moreover,PIML is less sensitive to noise.These findings indicate that it is crucial to integrate data-driven machine learning with petrophysical mechanism for the application of artificial intelligence in oil and gas exploration.展开更多
In this paper,the heat transfer enhancement(HTE)of supercritical nitrogen flowing downward in a vertical small tube(diameter 2 mm)is studied using the commercial software CFX of Ansys16.1,to provide theoretical guidan...In this paper,the heat transfer enhancement(HTE)of supercritical nitrogen flowing downward in a vertical small tube(diameter 2 mm)is studied using the commercial software CFX of Ansys16.1,to provide theoretical guidance on the design of high-performance heat transfer systems.An effective numerical simulation method,which employs the SSG Reynolds stress model with enhanced wall treatment,is applied to study the heat transfer of supercritical nitrogen under typical working conditions.The objective is to evaluate the effect of the main parameters taking into account the buoyancy and flow acceleration effects.Simulation results are compared with results calculated from three well-known empirical correlations and the applicability of empirical correlation is discussed in detail.It is discovered that the Watts and Chou correlation accurately fits the simulation results of supercritical nitrogen and the Dittus-Boelter and Jackson correlations can only be used for high-pressure conditions.The HTE of supercritical nitrogen is closely related to the laminar sub-layer and buffer layer of a boundary layer.The buoyancy effect on the HTE should be considered at low mass flux conditions,and thermal acceleration can be completely ignored for the cases studied.The special HTE featured by the increment in heat transfer coefficient with increasing heat flux is discovered at low pressure,and simulation results proved that this HTE is caused by the combined actions of buoyancy as well as significant variations in specific heat and viscosity.展开更多
This research was undertaken for the evaluation of soil erosion using the semi-distributed basin scale SWAT model for four subcatchments of the Dhrabi River Catchment(DRC),which is located in the Pothwar Plateau regio...This research was undertaken for the evaluation of soil erosion using the semi-distributed basin scale SWAT model for four subcatchments of the Dhrabi River Catchment(DRC),which is located in the Pothwar Plateau region.Two subcatchments(catchment-25 and-31)are characterized by gullies while the other two(catchment-27 and-32)are managed with terraced landuse system.The performance of the model was satisfactory with coefficient of determination(R^(2))=0.67 to 0.91 and Nash-Sutcliffe efficiency(ENS)=0.54 to 0.85 for both surface runoff and sediment yield during the calibration(2009-2010)and validation(2011)periods.The PUSLE factor was found to be the most sensitive parameter during model calibration.It was observed that all of the rainfall-runoff events occurred during the monsoon season(June to September).The estimated annual sediment loss ranged from 2.6 t/hm^(2) to 31.1 t/hm^(2) over the duration of the simulation period for the non-terraced catchments,in response to annual precipitation amounts that were between 194.8 mm to 579.3 mm.In contrast,the predicted annual sediment levels for the terraced catchments ranged from 0.52 t/hm^(2) to 10.10 t/hm^(2) due to similar precipitation amounts.The terraced catchments resulted in 4 to 5 times lower sediment yield as compared to non-terraced catchments.The results suggest that there is a huge potential for terraces to reduce soil erosion in the DRC specifically and Pothwar area generally,which have proven to be an efficient approach to establishing soil and water conservation structures in this region.展开更多
基金the National Natural Science Foundation of China （Grant No. 30270759） the Science and Technology Department of Zhejiang Province （Grant No. 2005C32001）.
文摘Eleven evaluating parameters for rice core collection were assessed based on genotypic values and molecular marke＇ information. Monte Carlo simulation combined with mixed linear model was used to eliminate the interference from environment in order to draw more reliable results. The coincidence rate of range （CR） was the optimal parameter. Mean Simpson index （MD）, mean Shannon-Weaver index of genetic diversity （M1） and mean polymorphism information content （MPIC） were important evaluating parameters. The variable rate of coefficient of variation （VR） could act as an important reference parameter for evaluating the variation degree of core collection. Percentage of polymorphic loci （p） could be used as a determination parameter for the size of core collection. Mean difference percentage （MD） was a determination parameter for the reliability judgment of core collection. The effective evaluating parameters for core collection selected in the research could be used as criteria for sampling percentage in different plant germplasm populations.
基金This project was supported by the NNSFC of China! (No.19891180, 59725104, 59895150) the Corporation of iron and Steel Baosha
文摘The threshold stress, σc, for sulfide stress corrosion cracking (SCC) of seven pipeline steels and five other steels, the critical stress, Sc, for seven pipeline steels and two drill rod steels with various strengths and the susceptibility to SCC, IRA or σf(SCC)/σf, for four pipeline steels, two drill rod steels and five other steels were measured. The results showed that there are no definite relationships among σc, Sc and IRA or σf(SCC)/σf.The threshold stress for hydrogen induced cracking (HlC) during charging with loading in the H2S04 solution, σc(H), decreased linearly with logarithm of the concentration of diffusible hydrogen c0, i.e., σc(H)=A-B Inco for four pipeline steels. σc(H) obtained with a special cathodic current ic, which was corresponding to the diffusible hydrogen concentration during immersing in the H2S solution, were consistent with /c for sulfide SCC for four pipeline steels. Therefore, σc for sulfide SCC can be measured using dynamically charging in the H2SO4 solution with the special cathodic current ic.
基金funding support from National Natural Science Foundation of China(52074322)Beijing Natural Science Foundation(3204052)+1 种基金Science Foundation of China University of Petroleum,Beijing(No.2462018YJRC032)National Major Project of China(2017ZX05030002-005)。
文摘Parameter inversions in oil/gas reservoirs based on well test interpretations are of great significance in oil/gas industry.Automatic well test interpretations based on artificial intelligence are the most promising to solve the problem of non-unique solution.In this work,a new deep reinforcement learning(DRL)based approach is proposed for automatic curve matching for well test interpretation,by using the double deep Q-network(DDQN).The DDQN algorithms are applied to train agents for automatic parameter tuning in three conventional well-testing models.In addition,to alleviate the dimensional disaster problem of parameter space,an asynchronous parameter adjustment strategy is used to train the agent.Finally,field applications are carried out by using the new DRL approaches.Results show that step number required for the DDQN to complete the curve matching is the least among,when comparing the naive deep Q-network(naive DQN)and deep Q-network(DQN).We also show that DDQN can improve the robustness of curve matching in comparison with supervised machine learning algorithms.Using DDQN algorithm to perform 100 curve matching tests on three traditional well test models,the results show that the mean relative error of the parameters is 7.58%for the homogeneous model,10.66%for the radial composite model,and 12.79%for the dual porosity model.In the actual field application,it is found that a good curve fitting can be obtained with only 30 steps of parameter adjustment.
文摘An efficient procedure is used for explicit description and evaluation of uncertainty of earthquake parameters in the uniform catalog of earthquakes in Iran and neighboring regions.An inadequate number of local and regional seismographic stations,poor station distribution,and Inadequacy of velocity models have resulted in conspicuous uncertainty in different parameters of recorded events.In a comprehensive seismic hazard analysis such uncertainties should be considered.Uncertainty of magnitude and location of events are evaluated for three different time periods,namely,historical,early instrumental,and modern instrumental time periods,for which existing seismological information differ widely in quantity,quality,and type.It is concluded that an uncertainty of 0.2-0.3 units of magnitude and 10-15 km in epicenter determinations should be considered in the most favorable conditions.None of the hypocenters of earthquakes in Iran can be considered as reliable,unless supported by other information such as
基金Funded by National Natural Science Foundation of China (Nos. 51468039, 51868044)。
文摘In order to investigate the corrosion mechanism of recycled reinforced concrete (RRC) under harsh environments,four recycled coarse aggregate (RCA) contents were selected,and saline soil was used as an electrolyte to perform electrified accelerated corrosion experiments.The relative dynamic elastic modulus and relative corrosion current density were considered to describe the deterioration law of the RRC in saline soil.The results indicated that as the energization time increased,the corrosion current density,corrosion potential,and polarization resistance of the steel bar decreased gradually.Compared with ordinary reinforced concrete,when the RCA content was 30%,the ability of the RRC to resist corrosion was improved slightly;however,when the RCA content exceeded 30%,the corrosion resistance of the RRC deteriorated rapidly.Scanning electron microscopy revealed that for a dense RRC,less corrosion products were generated in the pores inside the concrete and on the surface of the steel bar.X-ray diffraction results indicated that SO_(4)^(2-) can generate ettringite and other corrosion products,along with volume expansion.The main corrosion products generated on the surface of the steel bars included Fe_(2)O_(3),Fe_(3)O_(4) and FeO(OH),which were the corrosion products generated by steel bars under natural environments.Therefore,using saline soil as an electrolyte is more consistent with the actual service environments of RRC.Both the relative dynamic mode and relative corrosion current density of the degradation parameters conform to the Weibull distribution;furthermore,the relative dynamic mode is more sensitive and the corresponding reliability curve can better describe the degradation law of RRC under saline soil environments.
基金supported by the Program for New Century Excellent Talents in Universities
文摘In order to obtain effective parameters for complex sand reservoirs,a log evaluation method for relevant reservoir parameters is established based on an analysis in the gas-bearing sandstone with high porosity and low permeability,low porosity and permeability and on various characteristics of log responses to reservoir lithologies and physical properties in the Neopleozoic sand reservoir of the Ordos basin.This log evaluation method covers the Cook method that is used to evaluate the porosity and oiliness in high porosity and low permeability reservoirs and another method in which the mineral content,derived from geochemical logs,is used to identify formation lithologies.Some areas have high calcium and low silt content,not uniformly distributed,the results of which show up in the complex formation lithologies and conventional log responses with great deviation.The reliability of the method is verified by comparison with conventional log data and core analyses.The calculation results coincide with the core analytical data and gas tests,which indicate that this log evaluation method is available,provides novel ideas for study of similar complex reservoir lithologies and has some reference value.
文摘Asphalt mixtures exhibit strong viscous properties under repetitive loads. This phenomenon can be simulated in creep and recovery tests. By applying the visco elastoplastic model proposed, data recorded in the tests are interpreted. It is emphasised that applicability of the visco elastoplastic model depends on the proper method of characterising parameters involved in the constitutive equations. Since two or more strain components of elasticity and viscosity coexist during the loading or unloading, a measuring system of two loggers is introduced to decouple these components. Test data are analysed in three steps as elastic, visco elastic and visco plastic evaluations, using the records collected at the moment of unloading, during the periods of recovery and creep respectively. Factors that may influence the accuracy of data analysis are also discussed.
文摘This paper developed an improved combinatorial method called the best chromosome clone plus younger generation chromosome prepotency genetic algorithm （BCC-YGCP-GA） to evaluate aquifer parameters. This method is based on a decimal simple genetic algorithm （SGA）. A synthetic example for unsteady-state flow in a two-dimensional, inhomogeneous, confined aquifer containing three hydraulically distinct zones, is used to develop data to test the model. The simulation utilizes SGA and BCC-YGCP-GA coupled to the finite element method to identify the mean zonal hydraulic conductivities, and storage coefficients of the three-compartment model. For this geometrically simple model, used as a prototype of more complex systems, the SGA does not reach convergence within 100 generations. Conversely, the convergence rate of the BCC-YGCD-GA model is very fast. The objective function value calculated by BCC-YGCD-GA is reduced to 1/1 O00th of the starting value within 100 generations, and the hydraulic conductivity and storage of three zones are within a few percent of the “true” values of the ideal model, highlighting the power of the method for aquifer parameterization.
文摘For the purpose of enhancing automobile safety and the effectiveness of recalls,increasing manufacturers' quality control capabilities,and reducing defects,we investigated thestatus of recalls over the last five years.We have examined patterns and trends in motor vehiclesafety recalls using databases from China,Europe and the United States.A recall rate parameterwas developed to evaluate the level of recall enforcement based on analyzing the reasonsfor recalls and manufactures' characteristics.Moreover,there were substantial differencesin the recall rates of China compared with those in other countries,indicating that Chinese manufacturersneed to take more active action in recall.
文摘Finite supply of non-regenerative resources triggers a competition between economic entities or between areas, which requires the ways regarding their utilization with higher levels in science and the standards regarding their use with higher efficiency in economics. To solve a problem of process evaluation in science and of driving force in economics during a process design or a process run for natural resources utilization, a process evaluation parameter originated from natural gas hydrate preparation from a small scale to industrialization scale and the equation of the criterion dependent are introduced to evaluate a variety of processes of natural resources utilization. The analyses indicate that the parameter is relevant to internal undeveloped resources amount change with a stable mass composition in a virtual black box model and external variable market with an implication of process efficiency in economy or of process efficiency of resource utilization and that the parameter has similar features of the thermodynamic state functions. Moreover, the equation of the criterion provided is a difference between the value of the process evaluation parameter at the final state and the value of the process evaluation parameter at the initial state in an actual process, which can be used to determine the direction of development and to judge the size of the driving force in an actual process or an economical run. The provided examples and correlative mathematical description can guide how an identification for the undeveloped resources and a real-time adjustment of dynamic production for the developing resource are done and how decisions regarding resource exploitation, the venture forecasting of capital utilization and updating technology are made. The parameter used itself and the equation of the derived criterion can help by playing a predictive role for selecting the optimal use processes and for designing new process of the natural resource utilization or capital use, and by playing a practical role for adjusting factual production status and for improving the actual process of the utilization of resource or capital in an economic society. Finally, those closed resource systems having accumulation or depletion of the resources or a variable mass such as a decomposition system, a fission system and a biological reproduction system will become possible future research objectives under the guide of this work.
基金support by the National Natural Science Foundation of China(No.52076179).
文摘Corner stall receives noticeable attention in the aeroengine field as an important phenomenon in highly-load compressors.Non-uniform leading-edge tubercles,as an effective method to delay stall,are introduced into the compressor.In this paper,the shape of leading-edge tubercles was controlled by a third-order Fourier function.To judge corner stall,a more precise stall indicator for compressor cascade with flow control methods was defined.Besides,the total kinetic energy of the secondary flow at large incidence was adopted as a parameter for stall evaluation to save computing resources.The results of multiobjective optimization reveal that the loss coefficient exhibited negligible variation at design incidence,while the total kinetic energy of secondary flow showed a significant reduction at large incidence,resulting in a substantial increase in stall incidence.In the optimal profiling cases,the stall incidencewas delayed from 7.9°to 11.6°.The major purpose of the research is to provide proper design guidelines for nonuniformleading-edge tubercles and uncover the flow controlmechanisms of leading-edge profiling.Hence,the geometric features that meet different optimization objectives were extracted through geometric analysis near the Pareto Front and through Self-OrganizingMap(SOM)dataminingmethods in the optimization database.Besides,flow field analysis reveals the flow control mechanism of leading-edge tubercles.The convex-concave-convex structure at the 0%-70%blade height region can form two branches of leading-edge vortex pairs that are opposite in the rotation direction to the passage vortex.The two branches of leading-edge vortex pairs mixed with the leading-edge separation vortex to form two stronger mixed vortices,which can effectively suppress the development of passage vortex and delay stall incidence.
基金supported by the Strategic Cooperation Technology Projects of CNPC and CUPB (ZLZX2020-03)National Key Research and Development Program (2019YFA0708301)+1 种基金National Key Research and Development Program (2023YFF0714102)Science and Technology Innovation Fund of CNPC (2021DQ02-0403).
文摘relationships between logging data and reservoir parameters.We compare our method’s performances using two datasets and evaluate the influences of multi-task learning,model structure,transfer learning,and petrophysics informed machine learning(PIML).Our experiments demonstrate that PIML significantly enhances the performance of formation evaluation,and the structure of residual neural network is optimal for incorporating petrophysical constraints.Moreover,PIML is less sensitive to noise.These findings indicate that it is crucial to integrate data-driven machine learning with petrophysical mechanism for the application of artificial intelligence in oil and gas exploration.
基金financially sponsored by the National Natural Science Foundation of China(No.51876024 and No.51976204)Science and Technology on Reactor System Design Technology Laboratory。
文摘In this paper,the heat transfer enhancement(HTE)of supercritical nitrogen flowing downward in a vertical small tube(diameter 2 mm)is studied using the commercial software CFX of Ansys16.1,to provide theoretical guidance on the design of high-performance heat transfer systems.An effective numerical simulation method,which employs the SSG Reynolds stress model with enhanced wall treatment,is applied to study the heat transfer of supercritical nitrogen under typical working conditions.The objective is to evaluate the effect of the main parameters taking into account the buoyancy and flow acceleration effects.Simulation results are compared with results calculated from three well-known empirical correlations and the applicability of empirical correlation is discussed in detail.It is discovered that the Watts and Chou correlation accurately fits the simulation results of supercritical nitrogen and the Dittus-Boelter and Jackson correlations can only be used for high-pressure conditions.The HTE of supercritical nitrogen is closely related to the laminar sub-layer and buffer layer of a boundary layer.The buoyancy effect on the HTE should be considered at low mass flux conditions,and thermal acceleration can be completely ignored for the cases studied.The special HTE featured by the increment in heat transfer coefficient with increasing heat flux is discovered at low pressure,and simulation results proved that this HTE is caused by the combined actions of buoyancy as well as significant variations in specific heat and viscosity.
文摘This research was undertaken for the evaluation of soil erosion using the semi-distributed basin scale SWAT model for four subcatchments of the Dhrabi River Catchment(DRC),which is located in the Pothwar Plateau region.Two subcatchments(catchment-25 and-31)are characterized by gullies while the other two(catchment-27 and-32)are managed with terraced landuse system.The performance of the model was satisfactory with coefficient of determination(R^(2))=0.67 to 0.91 and Nash-Sutcliffe efficiency(ENS)=0.54 to 0.85 for both surface runoff and sediment yield during the calibration(2009-2010)and validation(2011)periods.The PUSLE factor was found to be the most sensitive parameter during model calibration.It was observed that all of the rainfall-runoff events occurred during the monsoon season(June to September).The estimated annual sediment loss ranged from 2.6 t/hm^(2) to 31.1 t/hm^(2) over the duration of the simulation period for the non-terraced catchments,in response to annual precipitation amounts that were between 194.8 mm to 579.3 mm.In contrast,the predicted annual sediment levels for the terraced catchments ranged from 0.52 t/hm^(2) to 10.10 t/hm^(2) due to similar precipitation amounts.The terraced catchments resulted in 4 to 5 times lower sediment yield as compared to non-terraced catchments.The results suggest that there is a huge potential for terraces to reduce soil erosion in the DRC specifically and Pothwar area generally,which have proven to be an efficient approach to establishing soil and water conservation structures in this region.
