Ice accretion on aircraft poses a critical threat to flight safety by significantly altering aerodynamic performance.This study presents a novel numerical framework for ice accretion prediction,developed by extending ...Ice accretion on aircraft poses a critical threat to flight safety by significantly altering aerodynamic performance.This study presents a novel numerical framework for ice accretion prediction,developed by extending the Myers model and incorporating an advanced multi-step approach.The proposed framework integrates ice layer growth into the modeling of unsteady water film dynamics and introduces a revised criterion for determining the icing condi-tion.A multi-step scheme,accounting for the continuous variation of physical parameters,is implemented to enhance computational accuracy.The framework is validated through simulations on both 2D and 3D configurations.For the NACA0012 airfoil,the model demonstrates strong adaptability to both rime and glaze ice scenarios,with simulated ice shapes and thicknesses showing close agreement with experimental data,especially under low-temperature rime ice scenarios.In glaze ice cases,the framework effectively captures the leading-edge ice thickness and horn formation,albeit with minor positional deviations.For the GLC-305 swept wing,the approach accurately reproduces the primary ice shape features and overall thickness distribution.However,discrepancies in icing extent and thickness persist under rime scenarios due to the limitations of the single-step strategy.In glaze ice scenarios,the model captures the general trend of ice horn development,though positional and thickness deviations remain.Overall,the developed framework improves the precision of ice accretion simulations and offers a promising tool for advancing aircraft safety.Future research will aim to refine the multi-step framework to further improve its robustness and accuracy in complex,3D icing environments.展开更多
Rapid alternating stress is formed in structure subjected to harsh thermal-acoustic loads,which will affect fatigue performance and reduce fatigue life seriously.First,fatigue experiment of superalloy thin-walled stru...Rapid alternating stress is formed in structure subjected to harsh thermal-acoustic loads,which will affect fatigue performance and reduce fatigue life seriously.First,fatigue experiment of superalloy thin-walled structure was carried out to obtain fatigue damage location and failure time of the experiment specimen,and S-iN curves of superalloy thin-walled structure at 723 K were fitted.Then,dynamic response simulation of superalloy thin-walled structure under the same load as experiment was implemented,and fatigue life was estimated based on the fatigue life prediction model which mainly included:improved rain-flow counting method,Morrow average stress model and Miner linear cumulative damage theory.Further,comparisons between simulation solutions and experimental results achieved a consistency,which verified the validity of the Fatigue Life Prediction Model(FLPM).Moreover,taking a rectangle plate as the analysis object,the distributions of Fain-low circulation blocks and damage levels of the structure were discussed respectively.Finally,current research indicates that in pre-buckling the structure is in softened area and fatigue life decreases with the increase of temperature;in post-buckling the structure is in hardened area and fatigue life increases with the increase of temperature within a certain range.展开更多
Gas pool coupled activating TIG(GPCA?TIG) welding put forward in?house can dramatically enhance weld penetration of TIG welding through introducing active element oxygen to reverse the Marangoni convection flow in the...Gas pool coupled activating TIG(GPCA?TIG) welding put forward in?house can dramatically enhance weld penetration of TIG welding through introducing active element oxygen to reverse the Marangoni convection flow in the molten pool. In order to further improve the welding productivity, the normal solid tungsten electrode is replaced by a kind of coupling arc electrode. The changes of arc pressure distribution along anode surface and the weld appearance were evaluated. On this basis, the dependences of weld shape characterized with weld depth, width and undercut on the main welding parameters were discussed. The results indicate, the substitution of coupling arc electrode can lead to an obvious decrease of arc pressure. Compared to hollow tungsten electrode and twin tungsten electrodes, the coupling arc electrode is much easier to manufacture and has more compacter structure. Combined with the symmetric distribution of arc pressure in di erent directions, this electrode has extensive adaptability. In the GPCA?TIG welding with coupling arc electrode, both the substitution of coupling arc electrode and the introduction of outer active gas oxygen can reduce the possibilities of producing humping bead and undercut. Their joint action makes this welding method have the capability of realizing high travel speed and deep penetration welding.展开更多
Taking a certain area in Sichuan Province as the object of this study, this paper adopts fuzzy mathematics method to make an evaluation on ecological risks of heavy metal in soil of this area. On calculation of factor...Taking a certain area in Sichuan Province as the object of this study, this paper adopts fuzzy mathematics method to make an evaluation on ecological risks of heavy metal in soil of this area. On calculation of factors’ weights, the traditional method of giving weight according to pollutants’ concentrations fails to consider the toxicity of heavy metals, and can’t reflect their actual ecological effect. With reference to the toxicity coefficient in potential ecological risk index evaluation, this article revises the traditional fuzzy mathematics evaluation model and puts forward a new method to calculate factors’ weight by incorporating toxicity levels in weight setting. The results of this study indicate: surface soil of this area was good in general, with 91.2% samples belonging to the first level, 7.77% samples belonging to the second level, and only 1.03% belonging to the third level. Compared with the results of the evaluation method of the reality content of soil, soil quality is better than the results of the quantitative evaluation, and is closer to the actual local conditions.展开更多
A person’s eye gaze can effectively express that person’s intentions.Thus,gaze estimation is an important approach in intelligent manufacturing to analyze a person’s intentions.Many gaze estimation methods regress ...A person’s eye gaze can effectively express that person’s intentions.Thus,gaze estimation is an important approach in intelligent manufacturing to analyze a person’s intentions.Many gaze estimation methods regress the direction of the gaze by analyzing images of the eyes,also known as eye patches.However,it is very difficult to construct a person-independent model that can estimate an accurate gaze direction for every person due to individual differences.In this paper,we hypothesize that the difference in the appearance of each of a person’s eyes is related to the difference in the corresponding gaze directions.Based on this hypothesis,a differential eyes’appearances network(DEANet)is trained on public datasets to predict the gaze differences of pairwise eye patches belonging to the same individual.Our proposed DEANet is based on a Siamese neural network(SNNet)framework which has two identical branches.A multi-stream architecture is fed into each branch of the SNNet.Both branches of the DEANet that share the same weights extract the features of the patches;then the features are concatenated to obtain the difference of the gaze directions.Once the differential gaze model is trained,a new person’s gaze direction can be estimated when a few calibrated eye patches for that person are provided.Because personspecific calibrated eye patches are involved in the testing stage,the estimation accuracy is improved.Furthermore,the problem of requiring a large amount of data when training a person-specific model is effectively avoided.A reference grid strategy is also proposed in order to select a few references as some of the DEANet’s inputs directly based on the estimation values,further thereby improving the estimation accuracy.Experiments on public datasets show that our proposed approach outperforms the state-of-theart methods.展开更多
This paper introduces the stress and deformation of anti floating anchor rod and explained the damage. Through field testing and numerical analysis, the article were studied the displacement and internal force of a ba...This paper introduces the stress and deformation of anti floating anchor rod and explained the damage. Through field testing and numerical analysis, the article were studied the displacement and internal force of a basement tensile anti float anchor, results showed that： the axial force of bolt tension transfer is top-down transfer, axial force decreases, the stress concentrate on the end. When a force is applied to a certain load, end firstly generate damage, but with the deepening of the axial force, it is greatly reduced, which indicates that the anchor force is an effective length, rather than the longer the anchor pullout force is bigger; anchor group effect is a problem that can not be ignored, because the engineering community for its attention degree is not enough, so that the design of anti floating anchor the lack of a reliable basis, the test results can provide a reference for the future design of anti floating anchor. Prestressed anchors in the tension lock, prestressed loss are regularly.展开更多
RFID is an important technology in the Internet of things that has the characteristics of safe, affordable, efficient, which received widespread attention and research. This paper proposes a UHF RFID-based intelligent...RFID is an important technology in the Internet of things that has the characteristics of safe, affordable, efficient, which received widespread attention and research. This paper proposes a UHF RFID-based intelligent vehicle management system （the Internet）. The system consists of RFID hardware system, CDMA system, the GIA system, data processing system, and can realize intelligent vehicle identification, location, tracking, velocity measurement, monitoring and management, to address the current severe road congestion, speeding, vehicle theft and vehicle overload management and other issues. Software and hardware design of intelligent vehicle management system based on RFID, focuses on systems, security design, selection of RFID cards and vehicle access control software features, the fleet management system is not only convenient, but also intelligent identification of vehicles and vehicle theft, in the community, school, car park and vehicle management occasions has a good application.展开更多
The application level of mathematics in each science discipline signs the level of development of this science. With the advancement of science and technology, especially the rapid development of computer technology, ...The application level of mathematics in each science discipline signs the level of development of this science. With the advancement of science and technology, especially the rapid development of computer technology, mathematics has permeated from natural scientific technology to agricultural construction, from economic activities to all areas of social life. Generally, when the actual problem requires us to provide quantitative results of analysis, forecasting, decision making, control and other aspects for real object under study, we are often inseparable from the application of mathematics. Mathematical modeling is the key to this process, whose purpose is to make mathematics applied to social and social services, and using mathematics to solve practical problems is through mathematical models. When using mathematical methods to solve some practical problems, we usually first transfer practical problems into mathematical language, and then abstract them into a mathematical model.展开更多
The experiment employed the use of melt purification and cyclic superheating technique to achieve maximum undercooling of Ni65Cu31Co4 alloy at 300K.Simultaneously,high-speed photography techniques were used to capture...The experiment employed the use of melt purification and cyclic superheating technique to achieve maximum undercooling of Ni65Cu31Co4 alloy at 300K.Simultaneously,high-speed photography techniques were used to capture the process of alloy liquid phase interface migration,and analyzed the relationship between the shape characteristics of the front end of alloy solidification and undercooling.The microstructure of the alloy was observed through metallographic microscopy,and the micro-morphological characteristics and evolution of the rapidly solidified microstructure were systematically studied.It is found that the grain refinement mechanism of Ni-Cu-Co ternary alloy is similar to that of Ni-Cu binary alloy.Grain refinement at low undercooling is caused by intense dendritic remelting,while grain refinement at high undercooling is attributed to recrystallization,driven by the stress and plastic strain accumulated from the interaction of liquid flow and primary dendrites caused by rapid solidification.It also shows that the addition of the third element Co plays a significant role in solidification rate and re-ignition effect.展开更多
Cross-cultural storytelling is a primary way for humankind to seek mutual recognition of value orientations between cultures,which facilitates the ability to jointly address the problems of human existence in the cont...Cross-cultural storytelling is a primary way for humankind to seek mutual recognition of value orientations between cultures,which facilitates the ability to jointly address the problems of human existence in the context of globalization.In this study,we conducted an interview survey of 6,130 respondents who were college students or graduates from 107 countries.The results show that there were a number of cross-cultural values embodied in China’s stories seen by the respondents as part of a common vision for the future of humankind and widely identified guidance on collaborative responses to global challenges.These cross-cultural values are common prosperity,ecological harmony,individual-collective integration,the urgency of global peace,as well as respect for multicultural and indigenous development paths.展开更多
An N×N optical switch based on cascaded microring resonators on chip is proposed.As an example,the 4×4 optical switch is further investigated.It is successfully demonstrated that its insertion loss is relati...An N×N optical switch based on cascaded microring resonators on chip is proposed.As an example,the 4×4 optical switch is further investigated.It is successfully demonstrated that its insertion loss is relatively low as 2.2 d B,the crosstalk is negligible,and the extinction ratio(ER)is as large as 130 d B.Thermal tuning is employed to make the microrings be in resonance or not,which leads to a response time of several hundred microseconds.Alternatively,doping the desired waveguide regions with p-type or n-type dopants is able to achieve a better response time of several nanoseconds.The proposed design is easily integrated to a large scale with less microring resonators,which ensures the compact size and the low power consumption.展开更多
<div style="text-align:justify;"> <span style="font-family:Verdana;">In order to understand the current status and future trends of China’s science and technology evaluation research, ...<div style="text-align:justify;"> <span style="font-family:Verdana;">In order to understand the current status and future trends of China’s science and technology evaluation research, we use the visual analysis tool CiteSpace to use the source journals included in the Chinese social science citations from 1998-2019 as the data source, and evaluate the domestic science and technology evaluation papers from the number of publications, the co-occurrence of authors, Institutional co-occurrence and subject clustering are analyzed. The study found that: the total amount of literature in the field of domestic science and technology evaluation is showing an overall upward trend;a relatively obvious author cooperation network has been formed, but the core author group has not yet been formed;institutional cooperation clusters have appeared, but the cooperation between institutions is still relatively scattered;The research topics focus on three aspects: science and technology evaluation index system, evaluation method and evaluation system.</span> </div>展开更多
Aiming at prestressed anchor cable frame in the presence of reinforcement landslide problem, through the selection of test points, the paper study and tested soil pressure, frame internal force and prestress losses un...Aiming at prestressed anchor cable frame in the presence of reinforcement landslide problem, through the selection of test points, the paper study and tested soil pressure, frame internal force and prestress losses under prestressed anchor cable frame beam, reveal the law of internal force distribution, and provides a theory basis for the rational design of prestressed anchor cable in landslide.展开更多
Logistics is an important part of the supply chain and connect all aspects of the supply chain throughout it, which has become business cooperation ties. In the process of developing supply chain logistics strategy, g...Logistics is an important part of the supply chain and connect all aspects of the supply chain throughout it, which has become business cooperation ties. In the process of developing supply chain logistics strategy, generally require attention to the following questions： To segment customers, we should determine the appropriate level of customer service, such as order cycle, inventory levels and other modes of transport for different types of clients; Group products according to sales on them, we can take different strategies for each category of products. Order entry, order execution and delivery job processing accounted for a large proportion of logistics activities, which requires technology and management to make the entire processes of supply chain logistics more efficient, especially for the interface area between members of enterprises. We can eliminate redundant work by integrating flow, improve logistics efficiency.展开更多
Some products are only sold in some regions while some are sold in certain months, so there are a lot of data gaps. If we choose too much of this vacancy data, it may have impact on knowledge extraction. So to aim at ...Some products are only sold in some regions while some are sold in certain months, so there are a lot of data gaps. If we choose too much of this vacancy data, it may have impact on knowledge extraction. So to aim at specific sale database, we chose to study six kinds of representative products among them and these products are relatively comprehensive in all regions and month sales including two conventional products, two special products and two accessories; we also chose seven sale regions to make detailed analysis. We selected nine characteristics of sales in database which respectively are monthly sales volume, monthly revenue, monthly average selling price, profit, program sales volume, completed percentage of a program, sales month, sales territory and product type.展开更多
John Keats is a representative Romantic poet in the 19 th century. This article analyzes a fanciful universe of a nightingale created in Keats' Ode to a Nightingale in contrast with the real world.
Job burnout is a synthetic syndrome of emotional exhaustion, depersonalization and reduced personal accomplishment. It has a time-linked and situation-specific nature by developing gradually and fluctuating with chang...Job burnout is a synthetic syndrome of emotional exhaustion, depersonalization and reduced personal accomplishment. It has a time-linked and situation-specific nature by developing gradually and fluctuating with changes of environmental contributors. In this study, four related diary entries were analyzed narratively, written by a polytechnic teacher teaching English for General Purposes （EGP） in a semester, to verify the possible work- related situational factors causing iob burnout of EGP teachers in the Chinese context. The results revealed ten environmental burnout elements, including overload, severity of students＇ problem, lacking supervisors＇ support, limited iob autonomy, a stern hierarchical organizational system, and opaque operating rules. We interpreted the results in terms of teacher professional development and proposed that enhancing EGP teachers＇ professional identity and revaluing the EGP course in polytechnics were the basic ways to mitigate burnout and improve English teachers＇ professional development.展开更多
Since the classical element model cannot describe the nonlinear characteristics of rock during the entire compressive creep process,nonlinear elements and creep damage are generally introduced in the model to resolve ...Since the classical element model cannot describe the nonlinear characteristics of rock during the entire compressive creep process,nonlinear elements and creep damage are generally introduced in the model to resolve this issue.However,several previous studies have reckoned that creep damage in rock only occurs in the accelerated creep stage and is only described by the Weibull distribution.Nevertheless,the creep damage mechanism of rocks is still not clearly understood.In this study,a reasonable representation of the damage variables of solid materials is presented.Specifically,based on the Gurson damage model,the damage state functions reflecting the constant creep stage and accelerated creep stage of rock are established.Further,the one-dimensional and three-dimensional creep damage constitutive equations of rock are derived by modifying the Nishihara model.Finally,the creep-acoustic emission tests of phyllite under different confining pressures are conducted to examine the creep damage characteristics of phyllite.And the proposed constitutive model is verified by analyzing the results of creep tests performed on saturated phyllite.Overall,this study reveals the relationship between the creep characteristics of rocks and the corresponding damage evolution pattern,which bridges the gap between the traditional theory and the quantitative analysis of rock creep and its damage pattern.展开更多
In this paper,we present a new stabilized finite element method for transient Navier-Stokes equations with high Reynolds number based on the projection of the velocity and pressure.We use Taylor-Hood elements and the ...In this paper,we present a new stabilized finite element method for transient Navier-Stokes equations with high Reynolds number based on the projection of the velocity and pressure.We use Taylor-Hood elements and the equal order elements in space and second order difference in time to get the fully discrete scheme.The scheme is proven to possess the absolute stability and the optimal error estimates.Numerical experiments show that our method is effective for transient Navier-Stokes equations with high Reynolds number and the results are in good agreement with the value of subgrid-scale eddy viscosity methods,Pet ro-Galerkin finite element method and st reamline diffusion method.展开更多
文摘Ice accretion on aircraft poses a critical threat to flight safety by significantly altering aerodynamic performance.This study presents a novel numerical framework for ice accretion prediction,developed by extending the Myers model and incorporating an advanced multi-step approach.The proposed framework integrates ice layer growth into the modeling of unsteady water film dynamics and introduces a revised criterion for determining the icing condi-tion.A multi-step scheme,accounting for the continuous variation of physical parameters,is implemented to enhance computational accuracy.The framework is validated through simulations on both 2D and 3D configurations.For the NACA0012 airfoil,the model demonstrates strong adaptability to both rime and glaze ice scenarios,with simulated ice shapes and thicknesses showing close agreement with experimental data,especially under low-temperature rime ice scenarios.In glaze ice cases,the framework effectively captures the leading-edge ice thickness and horn formation,albeit with minor positional deviations.For the GLC-305 swept wing,the approach accurately reproduces the primary ice shape features and overall thickness distribution.However,discrepancies in icing extent and thickness persist under rime scenarios due to the limitations of the single-step strategy.In glaze ice scenarios,the model captures the general trend of ice horn development,though positional and thickness deviations remain.Overall,the developed framework improves the precision of ice accretion simulations and offers a promising tool for advancing aircraft safety.Future research will aim to refine the multi-step framework to further improve its robustness and accuracy in complex,3D icing environments.
基金co-supported by Aviation Basic Science Fund Project of China(No.20151554002)Natural Sciences Key Project of Chengdu Aeronautic Polytechnic in China(No.061754)Natural Sciences General Project of Sichuan Province Education Department in China(No.18ZB0057).
文摘Rapid alternating stress is formed in structure subjected to harsh thermal-acoustic loads,which will affect fatigue performance and reduce fatigue life seriously.First,fatigue experiment of superalloy thin-walled structure was carried out to obtain fatigue damage location and failure time of the experiment specimen,and S-iN curves of superalloy thin-walled structure at 723 K were fitted.Then,dynamic response simulation of superalloy thin-walled structure under the same load as experiment was implemented,and fatigue life was estimated based on the fatigue life prediction model which mainly included:improved rain-flow counting method,Morrow average stress model and Miner linear cumulative damage theory.Further,comparisons between simulation solutions and experimental results achieved a consistency,which verified the validity of the Fatigue Life Prediction Model(FLPM).Moreover,taking a rectangle plate as the analysis object,the distributions of Fain-low circulation blocks and damage levels of the structure were discussed respectively.Finally,current research indicates that in pre-buckling the structure is in softened area and fatigue life decreases with the increase of temperature;in post-buckling the structure is in hardened area and fatigue life increases with the increase of temperature within a certain range.
基金National Natural Science Foundation of China(Grant No.51265029)
文摘Gas pool coupled activating TIG(GPCA?TIG) welding put forward in?house can dramatically enhance weld penetration of TIG welding through introducing active element oxygen to reverse the Marangoni convection flow in the molten pool. In order to further improve the welding productivity, the normal solid tungsten electrode is replaced by a kind of coupling arc electrode. The changes of arc pressure distribution along anode surface and the weld appearance were evaluated. On this basis, the dependences of weld shape characterized with weld depth, width and undercut on the main welding parameters were discussed. The results indicate, the substitution of coupling arc electrode can lead to an obvious decrease of arc pressure. Compared to hollow tungsten electrode and twin tungsten electrodes, the coupling arc electrode is much easier to manufacture and has more compacter structure. Combined with the symmetric distribution of arc pressure in di erent directions, this electrode has extensive adaptability. In the GPCA?TIG welding with coupling arc electrode, both the substitution of coupling arc electrode and the introduction of outer active gas oxygen can reduce the possibilities of producing humping bead and undercut. Their joint action makes this welding method have the capability of realizing high travel speed and deep penetration welding.
文摘Taking a certain area in Sichuan Province as the object of this study, this paper adopts fuzzy mathematics method to make an evaluation on ecological risks of heavy metal in soil of this area. On calculation of factors’ weights, the traditional method of giving weight according to pollutants’ concentrations fails to consider the toxicity of heavy metals, and can’t reflect their actual ecological effect. With reference to the toxicity coefficient in potential ecological risk index evaluation, this article revises the traditional fuzzy mathematics evaluation model and puts forward a new method to calculate factors’ weight by incorporating toxicity levels in weight setting. The results of this study indicate: surface soil of this area was good in general, with 91.2% samples belonging to the first level, 7.77% samples belonging to the second level, and only 1.03% belonging to the third level. Compared with the results of the evaluation method of the reality content of soil, soil quality is better than the results of the quantitative evaluation, and is closer to the actual local conditions.
基金supported by the Science and Technology Support Project of Sichuan Science and Technology Department(2018SZ0357)and China Scholarship。
文摘A person’s eye gaze can effectively express that person’s intentions.Thus,gaze estimation is an important approach in intelligent manufacturing to analyze a person’s intentions.Many gaze estimation methods regress the direction of the gaze by analyzing images of the eyes,also known as eye patches.However,it is very difficult to construct a person-independent model that can estimate an accurate gaze direction for every person due to individual differences.In this paper,we hypothesize that the difference in the appearance of each of a person’s eyes is related to the difference in the corresponding gaze directions.Based on this hypothesis,a differential eyes’appearances network(DEANet)is trained on public datasets to predict the gaze differences of pairwise eye patches belonging to the same individual.Our proposed DEANet is based on a Siamese neural network(SNNet)framework which has two identical branches.A multi-stream architecture is fed into each branch of the SNNet.Both branches of the DEANet that share the same weights extract the features of the patches;then the features are concatenated to obtain the difference of the gaze directions.Once the differential gaze model is trained,a new person’s gaze direction can be estimated when a few calibrated eye patches for that person are provided.Because personspecific calibrated eye patches are involved in the testing stage,the estimation accuracy is improved.Furthermore,the problem of requiring a large amount of data when training a person-specific model is effectively avoided.A reference grid strategy is also proposed in order to select a few references as some of the DEANet’s inputs directly based on the estimation values,further thereby improving the estimation accuracy.Experiments on public datasets show that our proposed approach outperforms the state-of-theart methods.
文摘This paper introduces the stress and deformation of anti floating anchor rod and explained the damage. Through field testing and numerical analysis, the article were studied the displacement and internal force of a basement tensile anti float anchor, results showed that： the axial force of bolt tension transfer is top-down transfer, axial force decreases, the stress concentrate on the end. When a force is applied to a certain load, end firstly generate damage, but with the deepening of the axial force, it is greatly reduced, which indicates that the anchor force is an effective length, rather than the longer the anchor pullout force is bigger; anchor group effect is a problem that can not be ignored, because the engineering community for its attention degree is not enough, so that the design of anti floating anchor the lack of a reliable basis, the test results can provide a reference for the future design of anti floating anchor. Prestressed anchors in the tension lock, prestressed loss are regularly.
文摘RFID is an important technology in the Internet of things that has the characteristics of safe, affordable, efficient, which received widespread attention and research. This paper proposes a UHF RFID-based intelligent vehicle management system （the Internet）. The system consists of RFID hardware system, CDMA system, the GIA system, data processing system, and can realize intelligent vehicle identification, location, tracking, velocity measurement, monitoring and management, to address the current severe road congestion, speeding, vehicle theft and vehicle overload management and other issues. Software and hardware design of intelligent vehicle management system based on RFID, focuses on systems, security design, selection of RFID cards and vehicle access control software features, the fleet management system is not only convenient, but also intelligent identification of vehicles and vehicle theft, in the community, school, car park and vehicle management occasions has a good application.
文摘The application level of mathematics in each science discipline signs the level of development of this science. With the advancement of science and technology, especially the rapid development of computer technology, mathematics has permeated from natural scientific technology to agricultural construction, from economic activities to all areas of social life. Generally, when the actual problem requires us to provide quantitative results of analysis, forecasting, decision making, control and other aspects for real object under study, we are often inseparable from the application of mathematics. Mathematical modeling is the key to this process, whose purpose is to make mathematics applied to social and social services, and using mathematics to solve practical problems is through mathematical models. When using mathematical methods to solve some practical problems, we usually first transfer practical problems into mathematical language, and then abstract them into a mathematical model.
基金Funded by the Natural Science Foundation of Shanxi Province(No.202203021211093)。
文摘The experiment employed the use of melt purification and cyclic superheating technique to achieve maximum undercooling of Ni65Cu31Co4 alloy at 300K.Simultaneously,high-speed photography techniques were used to capture the process of alloy liquid phase interface migration,and analyzed the relationship between the shape characteristics of the front end of alloy solidification and undercooling.The microstructure of the alloy was observed through metallographic microscopy,and the micro-morphological characteristics and evolution of the rapidly solidified microstructure were systematically studied.It is found that the grain refinement mechanism of Ni-Cu-Co ternary alloy is similar to that of Ni-Cu binary alloy.Grain refinement at low undercooling is caused by intense dendritic remelting,while grain refinement at high undercooling is attributed to recrystallization,driven by the stress and plastic strain accumulated from the interaction of liquid flow and primary dendrites caused by rapid solidification.It also shows that the addition of the third element Co plays a significant role in solidification rate and re-ignition effect.
基金The paper is a staged result of“Research on Narrative Strategy for Telling China’s Stories Well in the Cross-Cultural Context”(17XXW008),a program funded by the National Social Science Fund of China(NSSF).
文摘Cross-cultural storytelling is a primary way for humankind to seek mutual recognition of value orientations between cultures,which facilitates the ability to jointly address the problems of human existence in the context of globalization.In this study,we conducted an interview survey of 6,130 respondents who were college students or graduates from 107 countries.The results show that there were a number of cross-cultural values embodied in China’s stories seen by the respondents as part of a common vision for the future of humankind and widely identified guidance on collaborative responses to global challenges.These cross-cultural values are common prosperity,ecological harmony,individual-collective integration,the urgency of global peace,as well as respect for multicultural and indigenous development paths.
基金supported by the National Natural Science and Foundation of China(No.11474048)
文摘An N×N optical switch based on cascaded microring resonators on chip is proposed.As an example,the 4×4 optical switch is further investigated.It is successfully demonstrated that its insertion loss is relatively low as 2.2 d B,the crosstalk is negligible,and the extinction ratio(ER)is as large as 130 d B.Thermal tuning is employed to make the microrings be in resonance or not,which leads to a response time of several hundred microseconds.Alternatively,doping the desired waveguide regions with p-type or n-type dopants is able to achieve a better response time of several nanoseconds.The proposed design is easily integrated to a large scale with less microring resonators,which ensures the compact size and the low power consumption.
文摘<div style="text-align:justify;"> <span style="font-family:Verdana;">In order to understand the current status and future trends of China’s science and technology evaluation research, we use the visual analysis tool CiteSpace to use the source journals included in the Chinese social science citations from 1998-2019 as the data source, and evaluate the domestic science and technology evaluation papers from the number of publications, the co-occurrence of authors, Institutional co-occurrence and subject clustering are analyzed. The study found that: the total amount of literature in the field of domestic science and technology evaluation is showing an overall upward trend;a relatively obvious author cooperation network has been formed, but the core author group has not yet been formed;institutional cooperation clusters have appeared, but the cooperation between institutions is still relatively scattered;The research topics focus on three aspects: science and technology evaluation index system, evaluation method and evaluation system.</span> </div>
文摘Aiming at prestressed anchor cable frame in the presence of reinforcement landslide problem, through the selection of test points, the paper study and tested soil pressure, frame internal force and prestress losses under prestressed anchor cable frame beam, reveal the law of internal force distribution, and provides a theory basis for the rational design of prestressed anchor cable in landslide.
文摘Logistics is an important part of the supply chain and connect all aspects of the supply chain throughout it, which has become business cooperation ties. In the process of developing supply chain logistics strategy, generally require attention to the following questions： To segment customers, we should determine the appropriate level of customer service, such as order cycle, inventory levels and other modes of transport for different types of clients; Group products according to sales on them, we can take different strategies for each category of products. Order entry, order execution and delivery job processing accounted for a large proportion of logistics activities, which requires technology and management to make the entire processes of supply chain logistics more efficient, especially for the interface area between members of enterprises. We can eliminate redundant work by integrating flow, improve logistics efficiency.
文摘Some products are only sold in some regions while some are sold in certain months, so there are a lot of data gaps. If we choose too much of this vacancy data, it may have impact on knowledge extraction. So to aim at specific sale database, we chose to study six kinds of representative products among them and these products are relatively comprehensive in all regions and month sales including two conventional products, two special products and two accessories; we also chose seven sale regions to make detailed analysis. We selected nine characteristics of sales in database which respectively are monthly sales volume, monthly revenue, monthly average selling price, profit, program sales volume, completed percentage of a program, sales month, sales territory and product type.
文摘John Keats is a representative Romantic poet in the 19 th century. This article analyzes a fanciful universe of a nightingale created in Keats' Ode to a Nightingale in contrast with the real world.
文摘Job burnout is a synthetic syndrome of emotional exhaustion, depersonalization and reduced personal accomplishment. It has a time-linked and situation-specific nature by developing gradually and fluctuating with changes of environmental contributors. In this study, four related diary entries were analyzed narratively, written by a polytechnic teacher teaching English for General Purposes （EGP） in a semester, to verify the possible work- related situational factors causing iob burnout of EGP teachers in the Chinese context. The results revealed ten environmental burnout elements, including overload, severity of students＇ problem, lacking supervisors＇ support, limited iob autonomy, a stern hierarchical organizational system, and opaque operating rules. We interpreted the results in terms of teacher professional development and proposed that enhancing EGP teachers＇ professional identity and revaluing the EGP course in polytechnics were the basic ways to mitigate burnout and improve English teachers＇ professional development.
基金supported by the National Natural Science Foundation of China(Grant Nos.U19A20111 and 42130719)the State Key Laboratory of Geo-hazard Prevention and Geo-environment Protection Independent Research Project(Grant No.SKLGP2017Z001)。
文摘Since the classical element model cannot describe the nonlinear characteristics of rock during the entire compressive creep process,nonlinear elements and creep damage are generally introduced in the model to resolve this issue.However,several previous studies have reckoned that creep damage in rock only occurs in the accelerated creep stage and is only described by the Weibull distribution.Nevertheless,the creep damage mechanism of rocks is still not clearly understood.In this study,a reasonable representation of the damage variables of solid materials is presented.Specifically,based on the Gurson damage model,the damage state functions reflecting the constant creep stage and accelerated creep stage of rock are established.Further,the one-dimensional and three-dimensional creep damage constitutive equations of rock are derived by modifying the Nishihara model.Finally,the creep-acoustic emission tests of phyllite under different confining pressures are conducted to examine the creep damage characteristics of phyllite.And the proposed constitutive model is verified by analyzing the results of creep tests performed on saturated phyllite.Overall,this study reveals the relationship between the creep characteristics of rocks and the corresponding damage evolution pattern,which bridges the gap between the traditional theory and the quantitative analysis of rock creep and its damage pattern.
基金We thank Dr.Chen Gang for the great help to the numerical part of this paper.This research was supported by the Natural Science Foundation of China(No.11271273)Major Project of Education Department in Sichan(No.18ZA0276).
文摘In this paper,we present a new stabilized finite element method for transient Navier-Stokes equations with high Reynolds number based on the projection of the velocity and pressure.We use Taylor-Hood elements and the equal order elements in space and second order difference in time to get the fully discrete scheme.The scheme is proven to possess the absolute stability and the optimal error estimates.Numerical experiments show that our method is effective for transient Navier-Stokes equations with high Reynolds number and the results are in good agreement with the value of subgrid-scale eddy viscosity methods,Pet ro-Galerkin finite element method and st reamline diffusion method.
