As a reliable additive manufacturing technology,the stereolithography(SLA)ceramic core necessitates a tailored sintering process to achieve optimal performance.This study explored the effects of final sintering temper...As a reliable additive manufacturing technology,the stereolithography(SLA)ceramic core necessitates a tailored sintering process to achieve optimal performance.This study explored the effects of final sintering temperatures(specifically 1,150,1,250,and 1,300°C)on the properties of SLA-fabricated SiO_(2)-based ceramic cores reinforced with nano-ZrO_(2)(at concentrations of 1.0wt.%,1.5wt.%,and 2.0wt.%).The results demonstrate that increasing the final sintering temperature and the incorporation of nano-ZrO_(2)enhance the viscous fiow of quartz glass,resulting in a higher sintering degree.As the final sintering temperature rises,the ceramic samples exhibit increased shrinkage rate,decreased apparent porosity,and increased bulk density.Higher final sintering temperatures also promote greater cristobalite precipitation,promoting an increase in the amount and precipitation rate of quartz during investment casting.The formation of a cristobalite and ZrSiO_4 network at elevated temperatures effectively inhibits the viscous flow of quartz glass,thereby significantly improving high-temperature flexural strength and creep resistance of ceramic cores.When the content of nano-ZrO_(2)is between 1.5wt.%and 2.0wt.%,the final sintering temperature of 1,250°C is the best choice.Under these conditions,the shrinkage rate along the Z direction ranges from 3.35%to 3.68%,the porosity lies between 25.57%and 26.03%,the bulk density varies from 1.612 to 1.645 g·cm^(-3),the room temperature fiexural strength is between 26.79 and 27.85 MPa,and the fiexural strength at high temperatures is within the range of 30.77 to 33.02 MPa.The defiection at high-temperatures is 3.37-5.31 mm,while the surface roughness of the upper surface is 3.26-4.79μm,and the surface roughness of the side surface is 4.97-5.79μm.These findings provide valuable guidance for optimizing the sintering processes of SLA ceramic cores,offering potential for industrial applications.展开更多
In an aircraft final assembly line(AFAL),the rational scheduling of assembly workers to complete tasks in an orderly manner is crucial for enhancing production efficiency.This paper addresses the multi-skilled worker ...In an aircraft final assembly line(AFAL),the rational scheduling of assembly workers to complete tasks in an orderly manner is crucial for enhancing production efficiency.This paper addresses the multi-skilled worker scheduling problem in the AFAL,where the processing time of each task varies due to the assigned workers’skill levels,referred to as variable duration.The objective is to minimize the makespan,i.e.,the total time required for all workers to complete all tasks.A mixed integer linear programming model is formulated under complex constraints including assembly precedence relations,skill requirements,worker skill capabilities,and workspace capacities.To solve the model effectively,a multi-pass priority rule-based heuristic(MPRH)algorithm is proposed.This algorithm integrates 14 activity priority rules and nine worker priority rules with worker weights.Extensive experiments iteratively the best-performing priority rules,and the most effective rule subsets are integrated through a lightweight multi-pass mechanism to enhance its efficiency.The computational results demonstrate that the MPRH can find high-quality solutions effectively within very short central processing unit central processing unit(CPU)time compared to GUROBI.A case study based on real data obtained from an AFAL confirms the necessity and the feasibility of the approach in practical applications.Sensitivity analyses provide valuable insights to real production scenarios.展开更多
纯粹驾驶乐趣始终深植于宝马品牌的基因血脉之中。宝马Z4正是这一理念的完美化身——以敞篷跑车的极致魅力诠释无与伦比的驾驭激情。自2002年初代车型问世以来,这款双座敞篷跑车便凭借独树一帜的设计美学、纯粹至臻的驾驶体验和运动性...纯粹驾驶乐趣始终深植于宝马品牌的基因血脉之中。宝马Z4正是这一理念的完美化身——以敞篷跑车的极致魅力诠释无与伦比的驾驭激情。自2002年初代车型问世以来,这款双座敞篷跑车便凭借独树一帜的设计美学、纯粹至臻的驾驶体验和运动性能的完美平衡,持续征服全球车迷。即将推出的宝马Z4 Final Edition将为爱好者开启限时珍藏通道,提供订购这款特别版车型的专属机遇——它的限量身份和专属或将使它成为车坛的不朽经典。该版本配备了独特的配置元素,在外观和内饰方面均营造出个性化的亮点。同时,Final Edition也象征着这款标志性双座跑车迎来了其巅峰荣耀。宝马Z4的生产将于2026年3月正式结束。展开更多
With the continuous adjustment of the energy structure,photovoltaic(PV)power generation projects are increasing,playing a crucial role in promoting the application of clean energy.However,the current audit of complete...With the continuous adjustment of the energy structure,photovoltaic(PV)power generation projects are increasing,playing a crucial role in promoting the application of clean energy.However,the current audit of completed final accounts for photovoltaic power generation projects faces many challenges,such as incomplete institutional processes,scattered archive management materials,inadequate digital intelligence systems,and insufficient analysis of final account amounts.Based on this,this article aims to deeply analyze these issues and propose targeted audit suggestions to standardize the construction and audit work of photovoltaic power generation projects and promote the sustainable and healthy development of the photovoltaic power generation business.展开更多
在国际大宗粮油谷物贸易中广泛使用由GAFTA、FOSFA等国际贸易协会制定的标准化格式合同。这些合同中的品质条款（Quality）按其内容及重要性可分为四类,分别是：（1）Certificate fina（交货品质以装港检验证书为准）（2）Analysis resu...在国际大宗粮油谷物贸易中广泛使用由GAFTA、FOSFA等国际贸易协会制定的标准化格式合同。这些合同中的品质条款（Quality）按其内容及重要性可分为四类,分别是：（1）Certificate fina（交货品质以装港检验证书为准）（2）Analysis results at discharge for the settlement of allowances（以卸港检验结果作为价格折让依据）展开更多
The Scarlet Letter has been recognized by numerous critics as being one of the greatest of American novels.All the aesthetic effects are perfectly fulfilled by the " final" return of the heroin — Hester Pry...The Scarlet Letter has been recognized by numerous critics as being one of the greatest of American novels.All the aesthetic effects are perfectly fulfilled by the " final" return of the heroin — Hester Prynne.Since her husband and lover have died,her daughter has been married into a noble family of Europe,why does Hester Prynne return to America,and take up her long forsaken shame? The purpose of the article intends to analyze this question.In brief,the decisive factors in regard to the final return of Hester Prynne include many characteristics of Hester Prynne and revealing of social reality.展开更多
A 3D/2D hybrid multi-physical-field mathematical model,which takes into consideration the thermosolutal buoyance,was developed to predict the macrosegregation of gear steel 20CrMnTi continuously cast by a curved bille...A 3D/2D hybrid multi-physical-field mathematical model,which takes into consideration the thermosolutal buoyance,was developed to predict the macrosegregation of gear steel 20CrMnTi continuously cast by a curved billet caster with size of 160 mm×160 mm,and investigated the effect of final electromagnetic stirring(F-EMS)on the fluid flow,heat transfer and solute distribution in the liquid core of continuously cast steel.The results show that the application of F-EMS eliminates the effect of thermosolutal buoyancy on the asymmetric distribution of carbon concentration in the cross section of billet and accelerates the final solidification of resident molten steel in the liquid core of strand,but promotes the negative carbon segregation near the billet center.When the gear steel 20CrMnTi is cast at the temperature of 1803 K and speed of 1.7 m/min,the solidification end advances forward from 9.84 to 9.72 m,and center carbon segregation ratio of billet decreases from 1.24 to 1.17 with the increase in current density of F-EMS from 0 to 350 A.展开更多
Final electromagnetic stirring(F-EMS)and thermal soft reduction(TSR)are techniques that improve the inner quality of continuous casting billets,but they have rarely been applied simultaneously.The application effects ...Final electromagnetic stirring(F-EMS)and thermal soft reduction(TSR)are techniques that improve the inner quality of continuous casting billets,but they have rarely been applied simultaneously.The application effects of F-EMS and TSR were compared,and a process integrating F-EMS and TSR was adopted for a billet continuous caster.A heat transfer model was established to calculate the thermal behavior of 82A tire cord steel billet.The locations of F-EMS and TSR were determined,followed by conducting a series of plant trials,involving F-EMS alone,TSR alone,and the integrated process of F-EMS and TSR.The results showed that F-EMS or TSR could effectively improve the inner quality of the billet under their respective suitable working conditions.Moreover,F-EMS was found to be more helpful in terms of improving central segregation,while TSR tended to improve V-segregation,central porosity,and pipe.The integration of F-EMS and TSR allowed the advantages of each technique to be utilized,thereby better improving the inner quality.Among all the working conditions,82A steel billet showed optimum inner quality when the current of F-EMS was 240 A and the cooling intensity of TSR was 2.2 m^(3) h^(−1).These findings demonstrate that the integration of F-EMS and TSR is promising for application on continuous casting billets.展开更多
The effect of final electromagnetic stirring on the solidification structure,element segregation,and carbides of GCrl5 bearing steel was investigated.The experiment of continuous casting of the steel was carried out b...The effect of final electromagnetic stirring on the solidification structure,element segregation,and carbides of GCrl5 bearing steel was investigated.The experiment of continuous casting of the steel was carried out by using a continuous casting physical simulation apparatus with the final electromagnetic stirring.The liquid core profile was revealed by the pour-out method during the solidification process.Eight ingots were produced under different electromagnetic stirring parameters for comparison.The results show that,at the final stage of solidification,intense electromagnetic stirring exacerbates the central carbon segregation,resulting in more serious precipitation of the primary carbides.It is also found that the carbides in the segregation area are dominantly M3C type,together with a small amount of M7C3-type and M3C2-type carbides.In this physical simulation model,the optimal stirring parameters to obtain a fine and homogeneous structure are the liquid pool width of 15 mm,current intensity of 150 A,and stirring frequency of 5 Hz.展开更多
基金supported by the Natural Science Foundation of Shanghai(No.23ZR1421500)the National Natural Science Foundation of China(Nos.52474412,52127807,52271035)+3 种基金the Shanghai Municipal Commission of Economy and Informatization(No.GYOJ2022-2-02)the United Innovation Program of Shanghai Commercial Aircraft Engine(No.AR966)the SPMI Project from Shanghai Academy of Spaceflight Technology(No.SPMI2022-06)the Ningbo International Science and Technology Cooperation Program(No.2023H004)。
文摘As a reliable additive manufacturing technology,the stereolithography(SLA)ceramic core necessitates a tailored sintering process to achieve optimal performance.This study explored the effects of final sintering temperatures(specifically 1,150,1,250,and 1,300°C)on the properties of SLA-fabricated SiO_(2)-based ceramic cores reinforced with nano-ZrO_(2)(at concentrations of 1.0wt.%,1.5wt.%,and 2.0wt.%).The results demonstrate that increasing the final sintering temperature and the incorporation of nano-ZrO_(2)enhance the viscous fiow of quartz glass,resulting in a higher sintering degree.As the final sintering temperature rises,the ceramic samples exhibit increased shrinkage rate,decreased apparent porosity,and increased bulk density.Higher final sintering temperatures also promote greater cristobalite precipitation,promoting an increase in the amount and precipitation rate of quartz during investment casting.The formation of a cristobalite and ZrSiO_4 network at elevated temperatures effectively inhibits the viscous flow of quartz glass,thereby significantly improving high-temperature flexural strength and creep resistance of ceramic cores.When the content of nano-ZrO_(2)is between 1.5wt.%and 2.0wt.%,the final sintering temperature of 1,250°C is the best choice.Under these conditions,the shrinkage rate along the Z direction ranges from 3.35%to 3.68%,the porosity lies between 25.57%and 26.03%,the bulk density varies from 1.612 to 1.645 g·cm^(-3),the room temperature fiexural strength is between 26.79 and 27.85 MPa,and the fiexural strength at high temperatures is within the range of 30.77 to 33.02 MPa.The defiection at high-temperatures is 3.37-5.31 mm,while the surface roughness of the upper surface is 3.26-4.79μm,and the surface roughness of the side surface is 4.97-5.79μm.These findings provide valuable guidance for optimizing the sintering processes of SLA ceramic cores,offering potential for industrial applications.
基金supported by the National Natural Science Foundation of China(52175475).
文摘In an aircraft final assembly line(AFAL),the rational scheduling of assembly workers to complete tasks in an orderly manner is crucial for enhancing production efficiency.This paper addresses the multi-skilled worker scheduling problem in the AFAL,where the processing time of each task varies due to the assigned workers’skill levels,referred to as variable duration.The objective is to minimize the makespan,i.e.,the total time required for all workers to complete all tasks.A mixed integer linear programming model is formulated under complex constraints including assembly precedence relations,skill requirements,worker skill capabilities,and workspace capacities.To solve the model effectively,a multi-pass priority rule-based heuristic(MPRH)algorithm is proposed.This algorithm integrates 14 activity priority rules and nine worker priority rules with worker weights.Extensive experiments iteratively the best-performing priority rules,and the most effective rule subsets are integrated through a lightweight multi-pass mechanism to enhance its efficiency.The computational results demonstrate that the MPRH can find high-quality solutions effectively within very short central processing unit central processing unit(CPU)time compared to GUROBI.A case study based on real data obtained from an AFAL confirms the necessity and the feasibility of the approach in practical applications.Sensitivity analyses provide valuable insights to real production scenarios.
文摘纯粹驾驶乐趣始终深植于宝马品牌的基因血脉之中。宝马Z4正是这一理念的完美化身——以敞篷跑车的极致魅力诠释无与伦比的驾驭激情。自2002年初代车型问世以来,这款双座敞篷跑车便凭借独树一帜的设计美学、纯粹至臻的驾驶体验和运动性能的完美平衡,持续征服全球车迷。即将推出的宝马Z4 Final Edition将为爱好者开启限时珍藏通道,提供订购这款特别版车型的专属机遇——它的限量身份和专属或将使它成为车坛的不朽经典。该版本配备了独特的配置元素,在外观和内饰方面均营造出个性化的亮点。同时,Final Edition也象征着这款标志性双座跑车迎来了其巅峰荣耀。宝马Z4的生产将于2026年3月正式结束。
文摘With the continuous adjustment of the energy structure,photovoltaic(PV)power generation projects are increasing,playing a crucial role in promoting the application of clean energy.However,the current audit of completed final accounts for photovoltaic power generation projects faces many challenges,such as incomplete institutional processes,scattered archive management materials,inadequate digital intelligence systems,and insufficient analysis of final account amounts.Based on this,this article aims to deeply analyze these issues and propose targeted audit suggestions to standardize the construction and audit work of photovoltaic power generation projects and promote the sustainable and healthy development of the photovoltaic power generation business.
文摘在国际大宗粮油谷物贸易中广泛使用由GAFTA、FOSFA等国际贸易协会制定的标准化格式合同。这些合同中的品质条款（Quality）按其内容及重要性可分为四类,分别是：（1）Certificate fina（交货品质以装港检验证书为准）（2）Analysis results at discharge for the settlement of allowances（以卸港检验结果作为价格折让依据）
文摘The Scarlet Letter has been recognized by numerous critics as being one of the greatest of American novels.All the aesthetic effects are perfectly fulfilled by the " final" return of the heroin — Hester Prynne.Since her husband and lover have died,her daughter has been married into a noble family of Europe,why does Hester Prynne return to America,and take up her long forsaken shame? The purpose of the article intends to analyze this question.In brief,the decisive factors in regard to the final return of Hester Prynne include many characteristics of Hester Prynne and revealing of social reality.
基金The authors gratefully acknowledge the financial support of the National Key Research and Development Plan(Nos.2017YFB0304100 and 2016YFB0300105)National Natural Science Foundation of China(Nos.51674072,51704151,and 51804067)Fundamental Research Funds for the Central Universities(Nos.N182504014,N170708020,and N172503013).
文摘A 3D/2D hybrid multi-physical-field mathematical model,which takes into consideration the thermosolutal buoyance,was developed to predict the macrosegregation of gear steel 20CrMnTi continuously cast by a curved billet caster with size of 160 mm×160 mm,and investigated the effect of final electromagnetic stirring(F-EMS)on the fluid flow,heat transfer and solute distribution in the liquid core of continuously cast steel.The results show that the application of F-EMS eliminates the effect of thermosolutal buoyancy on the asymmetric distribution of carbon concentration in the cross section of billet and accelerates the final solidification of resident molten steel in the liquid core of strand,but promotes the negative carbon segregation near the billet center.When the gear steel 20CrMnTi is cast at the temperature of 1803 K and speed of 1.7 m/min,the solidification end advances forward from 9.84 to 9.72 m,and center carbon segregation ratio of billet decreases from 1.24 to 1.17 with the increase in current density of F-EMS from 0 to 350 A.
基金the financial support provided by the independent subject of State Key Laboratory of Advanced MetallurgyUniversity of Science and Technology Beijing,China,grant number 41617003,which enabled the successful completion of the study.
文摘Final electromagnetic stirring(F-EMS)and thermal soft reduction(TSR)are techniques that improve the inner quality of continuous casting billets,but they have rarely been applied simultaneously.The application effects of F-EMS and TSR were compared,and a process integrating F-EMS and TSR was adopted for a billet continuous caster.A heat transfer model was established to calculate the thermal behavior of 82A tire cord steel billet.The locations of F-EMS and TSR were determined,followed by conducting a series of plant trials,involving F-EMS alone,TSR alone,and the integrated process of F-EMS and TSR.The results showed that F-EMS or TSR could effectively improve the inner quality of the billet under their respective suitable working conditions.Moreover,F-EMS was found to be more helpful in terms of improving central segregation,while TSR tended to improve V-segregation,central porosity,and pipe.The integration of F-EMS and TSR allowed the advantages of each technique to be utilized,thereby better improving the inner quality.Among all the working conditions,82A steel billet showed optimum inner quality when the current of F-EMS was 240 A and the cooling intensity of TSR was 2.2 m^(3) h^(−1).These findings demonstrate that the integration of F-EMS and TSR is promising for application on continuous casting billets.
基金the National Natural Science Foundation of China(Nos.U1560202,51604171,and 51690162)the Shanghai Municipal Science and Technology Commission(No.17JC1400602).
文摘The effect of final electromagnetic stirring on the solidification structure,element segregation,and carbides of GCrl5 bearing steel was investigated.The experiment of continuous casting of the steel was carried out by using a continuous casting physical simulation apparatus with the final electromagnetic stirring.The liquid core profile was revealed by the pour-out method during the solidification process.Eight ingots were produced under different electromagnetic stirring parameters for comparison.The results show that,at the final stage of solidification,intense electromagnetic stirring exacerbates the central carbon segregation,resulting in more serious precipitation of the primary carbides.It is also found that the carbides in the segregation area are dominantly M3C type,together with a small amount of M7C3-type and M3C2-type carbides.In this physical simulation model,the optimal stirring parameters to obtain a fine and homogeneous structure are the liquid pool width of 15 mm,current intensity of 150 A,and stirring frequency of 5 Hz.
