A novel magnetorheological finishing(MRF)process using a small ball-end permanent-magnet polishing head is proposed,and a four-axes linkage dedicated MRF machine tool is fabricated to achieve the nanofinishing of an i...A novel magnetorheological finishing(MRF)process using a small ball-end permanent-magnet polishing head is proposed,and a four-axes linkage dedicated MRF machine tool is fabricated to achieve the nanofinishing of an irregularψ-shaped small-bore complex component with concave surfaces of a curvature radius less than3 mm.The processing method of the complex component is introduced.Magnetostatic simulation during the entire finishing path is carried out to analyze the material removal characteristics.A typicalψ-shaped small-bore complex component is polished on the developed device,and a fine surface quality is obtained with surface roughness Raof 0.0107μm and surface accuracy of the finished spherical surfaces of 0.3320μm(PV).These findings indicate that the proposed MRF process can perform the nanofinishing of a kind of small-bore complex component with small-curvature-radius concave surfaces.展开更多
It is a challenge to polish the interior surface of an additively manufactured component with complex structures and groove sizes less than 1 mm.Traditional polishing methods are disabled to polish the component,meanw...It is a challenge to polish the interior surface of an additively manufactured component with complex structures and groove sizes less than 1 mm.Traditional polishing methods are disabled to polish the component,meanwhile keeping the structure intact.To overcome this challenge,small-grooved components made of aluminum alloy with sizes less than 1 mm were fabricated by a custom-made printer.A novel approach to multi-phase jet(MPJ)polishing is proposed,utilizing a self-developed polisher that incorporates solid,liquid,and gas phases.In contrast,abrasive air jet(AAJ)polishing is recommended,employing a customized polisher that combines solid and gas phases.After jet polishing,surface roughness(Sa)on the interior surface of grooves decreases from pristine 8.596μm to 0.701μm and 0.336μm via AAJ polishing and MPJ polishing,respectively,and Sa reduces 92%and 96%,correspondingly.Furthermore,a formula defining the relationship between linear energy density and unit defect volume has been developed.The optimized parameters in additive manufacturing are that linear energy density varies from 0.135 J mm^(-1)to 0.22 J mm^(-1).The unit area defect volume achieved via the optimized parameters decreases to 1/12 of that achieved via non-optimized ones.Computational fluid dynamics simulation results reveal that material is removed by shear stress,and the alumina abrasives experience multiple collisions with the defects on the heat pipe groove,resulting in uniform material removal.This is in good agreement with the experimental results.The novel proposed setups,approach,and findings provide new insights into manufacturing complex-structured components,polishing the small-grooved structure,and keeping it unbroken.展开更多
Let f be a transcendental entire function with order ρ 〈 1/2 and let a be a sufficiently large constant. We prove that if there exists r0 〉 1 such that, for all r 〉 r0 and any small ε 〉0,M（r^σ,f）≥M（r,f）σ...Let f be a transcendental entire function with order ρ 〈 1/2 and let a be a sufficiently large constant. We prove that if there exists r0 〉 1 such that, for all r 〉 r0 and any small ε 〉0,M（r^σ,f）≥M（r,f）σ＋ε.then every component of the Fatou set F（f） is bounded.展开更多
Biofilms containing foodborne pathogens can adhere to food ingredients or food processing equipment.Due to their enhanced resilience to cleaning and chance of cross-contamination,there is an increased risk of food poi...Biofilms containing foodborne pathogens can adhere to food ingredients or food processing equipment.Due to their enhanced resilience to cleaning and chance of cross-contamination,there is an increased risk of food poisoning to consumers.The life course of biofilms is generally thought to be regulated by a quorum sensing(QS)system by secreted autoinducing peptides(AIPs).Recent studies have revealed that small non-coding RNA(sRNA)also plays an important role in regulating biofilm formation at the post-transcriptional level.Moreover,sRNA can act as an intermediate regulating hub between the quorum sensing system and biofilm.This review summarizes the latest findings on sRNA in biofilms of common foodborne pathogens and their potential impact.We also highlight the different mechanism of cascade regulation of sRNA and QS system in biofilm formation in several typical foodborne pathogens.In this process,sRNA responds to dynamic external environmental signals finely and accurately,and can feedback information on the bacterial cell environment to modify the QS system.These findings will deepen our understanding of biofilm formation and provide new perspectives for eliminating biofilm of foodborne pathogens based on the cascade regulation of small RNA and QS for developing biofilm-free food-processing systems.展开更多
基金supported by the National Key Research and Development Program of China [grant number 2018YFB1107600]
文摘A novel magnetorheological finishing(MRF)process using a small ball-end permanent-magnet polishing head is proposed,and a four-axes linkage dedicated MRF machine tool is fabricated to achieve the nanofinishing of an irregularψ-shaped small-bore complex component with concave surfaces of a curvature radius less than3 mm.The processing method of the complex component is introduced.Magnetostatic simulation during the entire finishing path is carried out to analyze the material removal characteristics.A typicalψ-shaped small-bore complex component is polished on the developed device,and a fine surface quality is obtained with surface roughness Raof 0.0107μm and surface accuracy of the finished spherical surfaces of 0.3320μm(PV).These findings indicate that the proposed MRF process can perform the nanofinishing of a kind of small-bore complex component with small-curvature-radius concave surfaces.
基金the National Key Research and Development Program of China(2018YFA0703400)the Young Scientists Fund of the National Natural Science Foundation of China(52205447)Changjiang Scholars Program of the Chinese Ministry of Education。
文摘It is a challenge to polish the interior surface of an additively manufactured component with complex structures and groove sizes less than 1 mm.Traditional polishing methods are disabled to polish the component,meanwhile keeping the structure intact.To overcome this challenge,small-grooved components made of aluminum alloy with sizes less than 1 mm were fabricated by a custom-made printer.A novel approach to multi-phase jet(MPJ)polishing is proposed,utilizing a self-developed polisher that incorporates solid,liquid,and gas phases.In contrast,abrasive air jet(AAJ)polishing is recommended,employing a customized polisher that combines solid and gas phases.After jet polishing,surface roughness(Sa)on the interior surface of grooves decreases from pristine 8.596μm to 0.701μm and 0.336μm via AAJ polishing and MPJ polishing,respectively,and Sa reduces 92%and 96%,correspondingly.Furthermore,a formula defining the relationship between linear energy density and unit defect volume has been developed.The optimized parameters in additive manufacturing are that linear energy density varies from 0.135 J mm^(-1)to 0.22 J mm^(-1).The unit area defect volume achieved via the optimized parameters decreases to 1/12 of that achieved via non-optimized ones.Computational fluid dynamics simulation results reveal that material is removed by shear stress,and the alumina abrasives experience multiple collisions with the defects on the heat pipe groove,resulting in uniform material removal.This is in good agreement with the experimental results.The novel proposed setups,approach,and findings provide new insights into manufacturing complex-structured components,polishing the small-grooved structure,and keeping it unbroken.
基金Supported by National Natural Science Foundation of China(Grant Nos.11261002 and 11261069)Natural Science Foundation of Yunnan Province of China(Grant No.2012FZ167)Educational Commission of Yunnan Province of China(Grant No.2012Z121)
文摘Let f be a transcendental entire function with order ρ 〈 1/2 and let a be a sufficiently large constant. We prove that if there exists r0 〉 1 such that, for all r 〉 r0 and any small ε 〉0,M（r^σ,f）≥M（r,f）σ＋ε.then every component of the Fatou set F（f） is bounded.
文摘探讨了小城镇土壤资源管理信息系统的研究和构建:其中包括系统设计目标及流程、系统架构设计和系统功能设计。应用组件式技术,采用流行的组件式GIS开发平台MapObjects与可视化开发语言Visual Basic,以湖北省江陵县为例,设计基于SQL Server 2000和ArcSDE存储管理的小城镇空间数据库和属性数据库,并在此基础上,开发小城镇土壤资源管理信息系统,实现了通用的GIS功能和专业的应用分析功能。系统可为小城镇建设中土壤资源的合理利用与保护提供数据采集、表达和分析支持。通过提供实时服务,提高土地管理工作效率和农技推广水平。
基金This work was supported by National Natural Science Foundation of China(32272424)Guangdong Major Project of Basic and Applied Basic Research(2020B0301030005)+1 种基金Guangdong Provincial Key Laboratory(2020B121201009)Guangdong Academy of Sciences Special Project for Capacity Building of Innovation Driven Development(2020GDASYL-20200401002).
文摘Biofilms containing foodborne pathogens can adhere to food ingredients or food processing equipment.Due to their enhanced resilience to cleaning and chance of cross-contamination,there is an increased risk of food poisoning to consumers.The life course of biofilms is generally thought to be regulated by a quorum sensing(QS)system by secreted autoinducing peptides(AIPs).Recent studies have revealed that small non-coding RNA(sRNA)also plays an important role in regulating biofilm formation at the post-transcriptional level.Moreover,sRNA can act as an intermediate regulating hub between the quorum sensing system and biofilm.This review summarizes the latest findings on sRNA in biofilms of common foodborne pathogens and their potential impact.We also highlight the different mechanism of cascade regulation of sRNA and QS system in biofilm formation in several typical foodborne pathogens.In this process,sRNA responds to dynamic external environmental signals finely and accurately,and can feedback information on the bacterial cell environment to modify the QS system.These findings will deepen our understanding of biofilm formation and provide new perspectives for eliminating biofilm of foodborne pathogens based on the cascade regulation of small RNA and QS for developing biofilm-free food-processing systems.
