An analytical model for contact area and contact stress considering the loading history in incremental sheet forming(ISF)was established.Then,by integrating with the directional characteristics of friction force and h...An analytical model for contact area and contact stress considering the loading history in incremental sheet forming(ISF)was established.Then,by integrating with the directional characteristics of friction force and horizontal force in the process,a friction test method reflecting the forming characteristics of ISF was proposed.Friction coefficients during the forming processes of parts with different wall angles were measured under various plane curves,process paths,and lubrication conditions.Furthermore,the accuracy of the analytical model,as well as the measured friction coefficients and their variation trends,was verified through comparative analysis with experimental results,simulation data,and outcomes from other existing models.The results indicate that the influence of the plane curve characteristics and process paths of parts on the friction condition is not significant.Under the lubrication conditions of L-HM46 oil,MoS_(2)grease,graphite powder,and dry friction,the friction coefficient shows a gradually increasing trend.Notably,when the wall angle is≤40°,the friction coefficient remains relatively constant;however,when the wall angle exceeds 40°,the friction coefficient increases progressively.展开更多
Theoretical education and practical education are very important in clinical laboratory teaching.The teaching evaluation system is one of the important means to test the quality of course teaching.The traditional summ...Theoretical education and practical education are very important in clinical laboratory teaching.The teaching evaluation system is one of the important means to test the quality of course teaching.The traditional summative evaluation needs to be improved in terms of scientificity and impartiality,and its guiding effect on teaching reform is limited.Therefore,this paper proposes to apply formative evaluation to clinical laboratory teaching to remobilize students'learning enthusiasm and provide valuable guidance for the subsequent teaching reform,hoping to achieve the purpose of improving the quality of laboratory teaching.展开更多
The study employed a descriptive mixed-methods qualitative case study approach.Material and interview-based data were collected from two EFL classes in a private international school in central China.Findings from RQ1...The study employed a descriptive mixed-methods qualitative case study approach.Material and interview-based data were collected from two EFL classes in a private international school in central China.Findings from RQ1 suggest that teacher-made summative tests were largely dependable to the extent that the tests reflect the syllabus-based construct and address students’affective factors.Findings from RQ2 suggest that facilitating factors including in-school continuous professional development(CPD)and teacher collegiality practices may enhance FUST’s prospective role.展开更多
The conventional forming limit diagram （FLD） is described as a plot of major strain versus minor strain. However, FLD is dependent on forming history and strain path. In the present study, a forming limit stress-bas...The conventional forming limit diagram （FLD） is described as a plot of major strain versus minor strain. However, FLD is dependent on forming history and strain path. In the present study, a forming limit stress-based diagram （FLSD） has been adopted to predict the fracture limit of aluminum alloy （AA） 5052-O1 sheet. Nakazima test is simulated by plastic constitutive formula derived from the modified Gurson-Tvergaard-Needleman （GTN） model. An in situ tensile test with scanning electron microscope （SEM） is proposed to determine the parameters in GTN model. The damage evolution is observed and recorded, and the parameters of GTN model are identified through counting void fraction at three damage stages of AA5052-O 1. According to the experimental results, the original void volume fraction, the volume fraction of potential nucleated voids, the critical void volume fraction, the void volume fraction at the final failure of material are assigned as 0.002 918, 0.024 9, 0.030 103, 0.048 54, respectively. The stress and strain are obtained at the last loading step before crack. FLSD and FLD of AA5052-O 1 are plotted. Compared with the experimental Nakazima test and uniaxial tensile test, the predicted results show a good agreement. The parameters determined by in situ tensile test can be applied to the research of the forming limit for ductile metals.展开更多
Automatically formed roadway(AFR)by roof cutting with bolt grouting(RCBG)is a new deep coal mining technology.By using this technology,the broken roadway roof is strengthened,and roof cutting is applied to cut off str...Automatically formed roadway(AFR)by roof cutting with bolt grouting(RCBG)is a new deep coal mining technology.By using this technology,the broken roadway roof is strengthened,and roof cutting is applied to cut off stress transfer between the roadway and gob to ensure the collapse of the overlying strata.The roadway is automatically formed owing to the broken expansion characteristics of the collapsed strata and mining pressure.Taking the Suncun Coal Mine as the engineering background,the control effect of this new technology on roadways was studied.To compare the law of stress evolution and the surrounding rock control mechanisms between AFR and traditional gob-side entry driving,a comparative study of geomechanical model tests on the above methods was carried out.The results showed that the new technology of AFR by RCBG effectively reduced the stress concentration of the roadway compared with gob-side entry driving.The side abutment pressure peak of the solid coal side was reduced by 24.3%,which showed an obvious pressure-releasing effect.Moreover,the position of the side abutment pressure peak was far from the solid coal side,making it more beneficial for roadway stability.The deformation of AFR surrounding rock was also smaller than the deformation of the gob-side entry driving by the overload test.The former was more beneficial for roadway stability than the latter under higher stress conditions.Field application tests showed that the new technology can effectively control roadway deformation.Moreover,the technology reduced roadway excavation and avoided resource waste caused by reserved coal pillars.展开更多
Forms enhance both the dynamic and interactive abilities of Web applications and the system complexity. And it is especially important to test forms completely and thoroughly. Therefore, this paper discusses how to ca...Forms enhance both the dynamic and interactive abilities of Web applications and the system complexity. And it is especially important to test forms completely and thoroughly. Therefore, this paper discusses how to carry out the form testing by different methods in the related testing phases. Namely, at first, automatically abstracting forms in the Web pages by parsing the HTML documents; then, ohtai ning the testing data with a certain strategies, such as by requirement specifications, by mining users＇ hefore input informarion or by recording meehanism; and next executing the testing actions automatically due to the well formed test cases; finally, a case study is given to illustrate the convenient and effective of these methods.展开更多
This article proposes the maximum test for a sequence of quadratic form statistics about score test in logistic regression model which can be applied to genetic and medicine fields.Theoretical properties about the max...This article proposes the maximum test for a sequence of quadratic form statistics about score test in logistic regression model which can be applied to genetic and medicine fields.Theoretical properties about the maximum test are derived.Extensive simulation studies are conducted to testify powers robustness of the maximum test compared to other two existed test.We also apply the maximum test to a real dataset about multiple gene variables association analysis.展开更多
Plane-strain forming limit strain （also known as FLD0） is an important data point on a forming limit diagram （FLD）. The effects of friction coefficients and material parameters on the specimen width associated wit...Plane-strain forming limit strain （also known as FLD0） is an important data point on a forming limit diagram （FLD）. The effects of friction coefficients and material parameters on the specimen width associated with the FLDo （W FLD0） in Marciniak test were studied by finite element simulation. WFLD0 was expressed as a function of the Lankford coefficients, n-value, k-value and sheet thickness and validated with various sheet materials. The determination of W FLD0 is of significance not only to reduce iterative attempts to accurately obtain FLDo, but also to obtain a full valid FLD with the least number of test specimens, which largely increases the efficiency and reduces cost to experimentally measure valid FLDs.展开更多
A novel construction method without scaffold work called as assembly-prestressing form finding loop by loop is presented.Based on the theory of finite displacement,the cycle-forward analysis method is presented for it...A novel construction method without scaffold work called as assembly-prestressing form finding loop by loop is presented.Based on the theory of finite displacement,the cycle-forward analysis method is presented for its construction calculation,which adopts the finite element method of generalized geometric nonlinearity combined with the application in the real construction process.By means of the combination of the forward analysis according to real construction sequence and the cycle iteration according to the initial strain increment method of cable force adjustment,the influence of the structural geometric nonlinearity and the loss of prestress are taken into account due to prestressing of tendons in turn and so on.If the initial cable forces derived from the method were used for construction,expected cable forces and shape could be assured easily.Simulation analysis achieved real-time tracking and controlling of the construction status.Finally,according to the procedure and parameters in simulating,a model experimental research on the stage of form finding(namely prestressing)was carried out for suspen-dome structure.The feasibility on the assembly-prestressing form finding method loop by loop was testified.The cycle-forward analysis method was established and numerical simulation was performed,and the results show that it was useful for the design and the construction of similar suspen-dome structure.展开更多
Taking Ti-6Al-4V specimens into consideration, the coupled thermal-electrical finite element model has been developed in Abaqus/Explicit to simulate the heating process in Gleeble 3800 and to study the temperature his...Taking Ti-6Al-4V specimens into consideration, the coupled thermal-electrical finite element model has been developed in Abaqus/Explicit to simulate the heating process in Gleeble 3800 and to study the temperature history and distribution in the specimen. In order to verify the finite element （FE） results, thermal tests are carried out on Gleeble 3800 for a Ti-6Al-4V specimen with a slot to in the centre of the specimen. The effects of the specimen size, heating rate, and air convection on the temperature distribution over the specimen have been investigated. The conclusions can be drawn as： the temperature gradient of the specimen decreases as the specimen size, heating rate, and vacuuming decrease.展开更多
Unwanted sound that is unpleasant or disruptive to hear, often interpreted as noise, is a widespread environmental pollutant. Similar to other environmental pollutants, this noise incurs a variety of costs to society....Unwanted sound that is unpleasant or disruptive to hear, often interpreted as noise, is a widespread environmental pollutant. Similar to other environmental pollutants, this noise incurs a variety of costs to society. Numerous negative health impacts are linked to increases in noise exposure,such as increased cardiovascular risk;and sleep展开更多
Under the influence of the upper coal pillars and dynamic pressure of coal mining,the roadway of the lower coal seam is prone to large deformation failure.In this paper,a novel control method and key technologies of a...Under the influence of the upper coal pillars and dynamic pressure of coal mining,the roadway of the lower coal seam is prone to large deformation failure.In this paper,a novel control method and key technologies of automatically formed roadway(AFR)by roof cutting and confined concrete column in extremely close-distance coal seam are proposed.Furthermore,a numerical model is established to analyze the structure characteristics of overlying roof strata.Based on numerical results,the roof structure model of“voussoir beam of upper layer+short cantilever beam of lower layer”of this method is proposed.What’s more,the calculation equation of the roof bending moment and evaluation indexes is established,and the influence of different factors on roof stability control of AFR is studied.Finally,a field test is conducted to verify the effectiveness of this novel method.Field results were as follows:1)The maximum and average support stress of working face obviously decreased;2)The confined concrete column can provide high-strength support in dynamic influence zone;3)The maximum deformation of AFR safety requirement can be met.This study can provide effective guidance for the application of this method in extremely close-distance coal seam.展开更多
Based on the elastoplastic mechanical properties of the weld and heat affected zone metals obtained by a nanoindentation test, a theoretical calculation model was established for the forming limit diagram（FLD） of ta...Based on the elastoplastic mechanical properties of the weld and heat affected zone metals obtained by a nanoindentation test, a theoretical calculation model was established for the forming limit diagram（FLD） of tailor-welded blanks（TWBs） on the basis of plastic constitutive relations and Hosford yield criteria. Hemispherical punch bulging tests were performed to verify the FLD theoretical calculation results. The results demonstrated that not only the FLD theoretical calculation of base materials but also that of TWBs had a good agreement with their experiments. Besides, poorer formability of TWBs caused its FLD significantly lower than that of base materials. The theoretical calculation model offers a reliable approach to obtain the specific FLD of TWBs.展开更多
基金the National Key R&D Program of China(No.2023YFB3407003)the National Natural Science Foundation of China(No.52375378).
文摘An analytical model for contact area and contact stress considering the loading history in incremental sheet forming(ISF)was established.Then,by integrating with the directional characteristics of friction force and horizontal force in the process,a friction test method reflecting the forming characteristics of ISF was proposed.Friction coefficients during the forming processes of parts with different wall angles were measured under various plane curves,process paths,and lubrication conditions.Furthermore,the accuracy of the analytical model,as well as the measured friction coefficients and their variation trends,was verified through comparative analysis with experimental results,simulation data,and outcomes from other existing models.The results indicate that the influence of the plane curve characteristics and process paths of parts on the friction condition is not significant.Under the lubrication conditions of L-HM46 oil,MoS_(2)grease,graphite powder,and dry friction,the friction coefficient shows a gradually increasing trend.Notably,when the wall angle is≤40°,the friction coefficient remains relatively constant;however,when the wall angle exceeds 40°,the friction coefficient increases progressively.
文摘Theoretical education and practical education are very important in clinical laboratory teaching.The teaching evaluation system is one of the important means to test the quality of course teaching.The traditional summative evaluation needs to be improved in terms of scientificity and impartiality,and its guiding effect on teaching reform is limited.Therefore,this paper proposes to apply formative evaluation to clinical laboratory teaching to remobilize students'learning enthusiasm and provide valuable guidance for the subsequent teaching reform,hoping to achieve the purpose of improving the quality of laboratory teaching.
文摘The study employed a descriptive mixed-methods qualitative case study approach.Material and interview-based data were collected from two EFL classes in a private international school in central China.Findings from RQ1 suggest that teacher-made summative tests were largely dependable to the extent that the tests reflect the syllabus-based construct and address students’affective factors.Findings from RQ2 suggest that facilitating factors including in-school continuous professional development(CPD)and teacher collegiality practices may enhance FUST’s prospective role.
基金Aeronautical Science Foundation of China （03H53048）
文摘The conventional forming limit diagram （FLD） is described as a plot of major strain versus minor strain. However, FLD is dependent on forming history and strain path. In the present study, a forming limit stress-based diagram （FLSD） has been adopted to predict the fracture limit of aluminum alloy （AA） 5052-O1 sheet. Nakazima test is simulated by plastic constitutive formula derived from the modified Gurson-Tvergaard-Needleman （GTN） model. An in situ tensile test with scanning electron microscope （SEM） is proposed to determine the parameters in GTN model. The damage evolution is observed and recorded, and the parameters of GTN model are identified through counting void fraction at three damage stages of AA5052-O 1. According to the experimental results, the original void volume fraction, the volume fraction of potential nucleated voids, the critical void volume fraction, the void volume fraction at the final failure of material are assigned as 0.002 918, 0.024 9, 0.030 103, 0.048 54, respectively. The stress and strain are obtained at the last loading step before crack. FLSD and FLD of AA5052-O 1 are plotted. Compared with the experimental Nakazima test and uniaxial tensile test, the predicted results show a good agreement. The parameters determined by in situ tensile test can be applied to the research of the forming limit for ductile metals.
基金This work was supported by the National Natural Science Foundation of China(Nos.51874188,52074164,42077267,and 51927807)the Natural Science Foundation of Shandong Province,China(Nos.2019SDZY04 and ZR2020JQ23)the Project of Shandong Province Higher Educational Youth Innovation Science and Technology Program,China(No.2019KJG013).
文摘Automatically formed roadway(AFR)by roof cutting with bolt grouting(RCBG)is a new deep coal mining technology.By using this technology,the broken roadway roof is strengthened,and roof cutting is applied to cut off stress transfer between the roadway and gob to ensure the collapse of the overlying strata.The roadway is automatically formed owing to the broken expansion characteristics of the collapsed strata and mining pressure.Taking the Suncun Coal Mine as the engineering background,the control effect of this new technology on roadways was studied.To compare the law of stress evolution and the surrounding rock control mechanisms between AFR and traditional gob-side entry driving,a comparative study of geomechanical model tests on the above methods was carried out.The results showed that the new technology of AFR by RCBG effectively reduced the stress concentration of the roadway compared with gob-side entry driving.The side abutment pressure peak of the solid coal side was reduced by 24.3%,which showed an obvious pressure-releasing effect.Moreover,the position of the side abutment pressure peak was far from the solid coal side,making it more beneficial for roadway stability.The deformation of AFR surrounding rock was also smaller than the deformation of the gob-side entry driving by the overload test.The former was more beneficial for roadway stability than the latter under higher stress conditions.Field application tests showed that the new technology can effectively control roadway deformation.Moreover,the technology reduced roadway excavation and avoided resource waste caused by reserved coal pillars.
基金Supported by the National Natural Science Foun-dation of China (60425206 ,90412003 ,60503033)the National Bas-ic Research Program of China (973 Program 2002CB312000 ) Opening Foundation of State Key Laboratory of Software Engineeringin Wuhan University, High Technology Research Project of JiangsuProvince (BG2005032)
文摘Forms enhance both the dynamic and interactive abilities of Web applications and the system complexity. And it is especially important to test forms completely and thoroughly. Therefore, this paper discusses how to carry out the form testing by different methods in the related testing phases. Namely, at first, automatically abstracting forms in the Web pages by parsing the HTML documents; then, ohtai ning the testing data with a certain strategies, such as by requirement specifications, by mining users＇ hefore input informarion or by recording meehanism; and next executing the testing actions automatically due to the well formed test cases; finally, a case study is given to illustrate the convenient and effective of these methods.
基金This work of Jiayan Zhu is partially supported by seeding project funding(2019ZZX026)scientific research project funding of talent recruitment,and start up funding for scientific research of Hubei University of Chinese MedicineThis work of Zhengbang Li is partially supported by self-determined research funds of Central China Normal University from colleges'basic research of MOE(CCNU18QN031).
文摘This article proposes the maximum test for a sequence of quadratic form statistics about score test in logistic regression model which can be applied to genetic and medicine fields.Theoretical properties about the maximum test are derived.Extensive simulation studies are conducted to testify powers robustness of the maximum test compared to other two existed test.We also apply the maximum test to a real dataset about multiple gene variables association analysis.
文摘Plane-strain forming limit strain （also known as FLD0） is an important data point on a forming limit diagram （FLD）. The effects of friction coefficients and material parameters on the specimen width associated with the FLDo （W FLD0） in Marciniak test were studied by finite element simulation. WFLD0 was expressed as a function of the Lankford coefficients, n-value, k-value and sheet thickness and validated with various sheet materials. The determination of W FLD0 is of significance not only to reduce iterative attempts to accurately obtain FLDo, but also to obtain a full valid FLD with the least number of test specimens, which largely increases the efficiency and reduces cost to experimentally measure valid FLDs.
基金Sposored by the Postdoctoral Science Foundation of China(Grant No.20060390387)the National Natural Science Foundation of China(Grant No.50278004)
文摘A novel construction method without scaffold work called as assembly-prestressing form finding loop by loop is presented.Based on the theory of finite displacement,the cycle-forward analysis method is presented for its construction calculation,which adopts the finite element method of generalized geometric nonlinearity combined with the application in the real construction process.By means of the combination of the forward analysis according to real construction sequence and the cycle iteration according to the initial strain increment method of cable force adjustment,the influence of the structural geometric nonlinearity and the loss of prestress are taken into account due to prestressing of tendons in turn and so on.If the initial cable forces derived from the method were used for construction,expected cable forces and shape could be assured easily.Simulation analysis achieved real-time tracking and controlling of the construction status.Finally,according to the procedure and parameters in simulating,a model experimental research on the stage of form finding(namely prestressing)was carried out for suspen-dome structure.The feasibility on the assembly-prestressing form finding method loop by loop was testified.The cycle-forward analysis method was established and numerical simulation was performed,and the results show that it was useful for the design and the construction of similar suspen-dome structure.
基金supported by the Fundamental Research Funds for the Central Universities of China under Grant No.A03007023801073
文摘Taking Ti-6Al-4V specimens into consideration, the coupled thermal-electrical finite element model has been developed in Abaqus/Explicit to simulate the heating process in Gleeble 3800 and to study the temperature history and distribution in the specimen. In order to verify the finite element （FE） results, thermal tests are carried out on Gleeble 3800 for a Ti-6Al-4V specimen with a slot to in the centre of the specimen. The effects of the specimen size, heating rate, and air convection on the temperature distribution over the specimen have been investigated. The conclusions can be drawn as： the temperature gradient of the specimen decreases as the specimen size, heating rate, and vacuuming decrease.
基金sponsored by the projects with OSP#193942 and#193940
文摘Unwanted sound that is unpleasant or disruptive to hear, often interpreted as noise, is a widespread environmental pollutant. Similar to other environmental pollutants, this noise incurs a variety of costs to society. Numerous negative health impacts are linked to increases in noise exposure,such as increased cardiovascular risk;and sleep
基金Projects(52074164,42077267)supported by the National Natural Science Foundation of ChinaProject(2023M742073)supported by the China Postdoctoral Science FoundationProject(SDCX-ZG-202303010)supported by the Shandong Postdoctora1 Science Foundation,China。
文摘Under the influence of the upper coal pillars and dynamic pressure of coal mining,the roadway of the lower coal seam is prone to large deformation failure.In this paper,a novel control method and key technologies of automatically formed roadway(AFR)by roof cutting and confined concrete column in extremely close-distance coal seam are proposed.Furthermore,a numerical model is established to analyze the structure characteristics of overlying roof strata.Based on numerical results,the roof structure model of“voussoir beam of upper layer+short cantilever beam of lower layer”of this method is proposed.What’s more,the calculation equation of the roof bending moment and evaluation indexes is established,and the influence of different factors on roof stability control of AFR is studied.Finally,a field test is conducted to verify the effectiveness of this novel method.Field results were as follows:1)The maximum and average support stress of working face obviously decreased;2)The confined concrete column can provide high-strength support in dynamic influence zone;3)The maximum deformation of AFR safety requirement can be met.This study can provide effective guidance for the application of this method in extremely close-distance coal seam.
基金Project(51275444) supported by the National Natural Science Foundation of ChinaProject(20121333110003) supported by the Specialized Research Fund for the Doctoral Program of Higher Education,China+1 种基金Project(E2014203271) supported by the Natural Science Foundation–Steel and Iron Foundation of Hebei ProvinceChina
文摘Based on the elastoplastic mechanical properties of the weld and heat affected zone metals obtained by a nanoindentation test, a theoretical calculation model was established for the forming limit diagram（FLD） of tailor-welded blanks（TWBs） on the basis of plastic constitutive relations and Hosford yield criteria. Hemispherical punch bulging tests were performed to verify the FLD theoretical calculation results. The results demonstrated that not only the FLD theoretical calculation of base materials but also that of TWBs had a good agreement with their experiments. Besides, poorer formability of TWBs caused its FLD significantly lower than that of base materials. The theoretical calculation model offers a reliable approach to obtain the specific FLD of TWBs.
