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
The aerospace community widely uses difficult-to-cut materials,such as titanium alloys,high-temperature alloys,metal/ceramic/polymer matrix composites,hard and brittle materials,and geometrically complex components,su...The aerospace community widely uses difficult-to-cut materials,such as titanium alloys,high-temperature alloys,metal/ceramic/polymer matrix composites,hard and brittle materials,and geometrically complex components,such as thin-walled structures,microchannels,and complex surfaces.Mechanical machining is the main material removal process for the vast majority of aerospace components.However,many problems exist,including severe and rapid tool wear,low machining efficiency,and poor surface integrity.Nontraditional energy-assisted mechanical machining is a hybrid process that uses nontraditional energies(vibration,laser,electricity,etc)to improve the machinability of local materials and decrease the burden of mechanical machining.This provides a feasible and promising method to improve the material removal rate and surface quality,reduce process forces,and prolong tool life.However,systematic reviews of this technology are lacking with respect to the current research status and development direction.This paper reviews the recent progress in the nontraditional energy-assisted mechanical machining of difficult-to-cut materials and components in the aerospace community.In addition,this paper focuses on the processing principles,material responses under nontraditional energy,resultant forces and temperatures,material removal mechanisms,and applications of these processes,including vibration-,laser-,electric-,magnetic-,chemical-,advanced coolant-,and hybrid nontraditional energy-assisted mechanical machining.Finally,a comprehensive summary of the principles,advantages,and limitations of each hybrid process is provided,and future perspectives on forward design,device development,and sustainability of nontraditional energy-assisted mechanical machining processes are discussed.展开更多
The Mediator co-activator complex is a highly conserved,multisubunit protein complex required for gene transcription by RNA polymerase Ⅱ(RNAPⅡ)in all eukaryotes(Allen and Taatjes,2015).This complex,which consist...The Mediator co-activator complex is a highly conserved,multisubunit protein complex required for gene transcription by RNA polymerase Ⅱ(RNAPⅡ)in all eukaryotes(Allen and Taatjes,2015).This complex,which consists of at least 30 polypeptides,can be divided into four structurally distinct sub-modules including the head,middle,tail,and cyclin-dependent kinase 8(CDK8)modules (CKM) (Fig. 1A) (Yin and Wang, 2014; Allen and Taatjes, 2015).展开更多
Complex thin-walled titanium alloy components play a key role in the aircraft,aerospace and marine industries,offering the advantages of reduced weight and increased thermal resistance.The geometrical complexity,dimen...Complex thin-walled titanium alloy components play a key role in the aircraft,aerospace and marine industries,offering the advantages of reduced weight and increased thermal resistance.The geometrical complexity,dimensional accuracy and in-service properties are essential to fulfill the high-performance standards required in new transportation systems,which brings new challenges to titanium alloy forming technologies.Traditional forming processes,such as superplastic forming or hot pressing,cannot meet all demands of modern applications due to their limited properties,low productivity and high cost.This has encouraged industry and research groups to develop novel high-efficiency forming processes.Hot gas pressure forming and hot stamping-quenching technologies have been developed for the manufacture of tubular and panel components,and are believed to be the cut-edge processes guaranteeing dimensional accuracy,microstructure and mechanical properties.This article intends to provide a critical review of high-efficiency titanium alloy forming processes,concentrating on latest investigations of controlling dimensional accuracy,microstructure and properties.The advantages and limitations of individual forming process are comprehensively analyzed,through which,future research trends of high-efficiency forming are identified including trends in process integration,processing window design,full cycle and multi-objective optimization.This review aims to provide a guide for researchers and process designers on the manufacture of thin-walled titanium alloy components whilst achieving high dimensional accuracy and satisfying performance properties with high efficiency and low cost.展开更多
In this paper, the variability characteristics of the global field of sea surface temperature (SST) anomaly are studied by complex principal component (c.p.c.) analysis, whose results are also compared with those of r...In this paper, the variability characteristics of the global field of sea surface temperature (SST) anomaly are studied by complex principal component (c.p.c.) analysis, whose results are also compared with those of real p.c. analysis. The data consist of 40 years of global SST monthly averages over latitudes from 42 5°S to 67 5°N. In the spatial domain, it is found that the distribution of the first complex loading amplitude is characterized by three areas of large values: the first one in the eastern and central equatorial Pacific Ocean, the second one in the northern tropical Indian Ocean and South China Sea, the third one in the northern Pacific Ocean. As it will be explained, this pattern may be considered as representative of El Nio mode. The first complex loading phase pattern shows a stationary wave in the Pacific (also revealed by real p.c. analysis) superimposed to an oscillating disturbance, propagating from the Pacific to Indian or the opposite way. A subsequent correlation analysis among different spatial points allows revealing disturbances actually propagating westward from the Pacific to the Indian Ocean, which could therefore represent reflected Rossby waves, i.e. the west phase of the signals that propagate disturbances of thermal structure in the tropical Pacific Ocean. In the time domain, a relation between the trend of the first complex principal component and the ENSO cycle is also established.展开更多
Component-based software engineering is concerned with the develop-ment of software that can satisfy the customer prerequisites through reuse or inde-pendent development.Coupling and cohesion measurements are primaril...Component-based software engineering is concerned with the develop-ment of software that can satisfy the customer prerequisites through reuse or inde-pendent development.Coupling and cohesion measurements are primarily used to analyse the better software design quality,increase the reliability and reduced system software complexity.The complexity measurement of cohesion and coupling component to analyze the relationship between the component module.In this paper,proposed the component selection framework of Hexa-oval optimization algorithm for selecting the suitable components from the repository.It measures the interface density modules of coupling and cohesion in a modular software sys-tem.This cohesion measurement has been taken into two parameters for analyz-ing the result of complexity,with the help of low cohesion and high cohesion.In coupling measures between the component of inside parameters and outside parameters.Thefinal process of coupling and cohesion,the measured values were used for the average calculation of components parameter.This paper measures the complexity of direct and indirect interaction among the component as well as the proposed algorithm selecting the optimal component for the repository.The better result is observed for high cohesion and low coupling in compo-nent-based software engineering.展开更多
Presently,the service performance of new-generation high-tech equipment is directly affected by the manufacturing quality of complex thin-walled components.A high-efficiency and quality manufacturing of these complex ...Presently,the service performance of new-generation high-tech equipment is directly affected by the manufacturing quality of complex thin-walled components.A high-efficiency and quality manufacturing of these complex thin-walled components creates a bottleneck that needs to be solved urgently in machinery manufacturing.To address this problem,the collaborative manufacturing of structure shape and surface integrity has emerged as a new process that can shorten processing cycles,improve machining qualities,and reduce costs.This paper summarises the research status on the material removal mechanism,precision control of structure shape,machined surface integrity control and intelligent process control technology of complex thin-walled components.Numerous solutions and technical approaches are then put forward to solve the critical problems in the high-performance manufacturing of complex thin-wall components.The development status,challenge and tendency of collaborative manufacturing technologies in the high-efficiency and quality manufacturing of complex thin-wall components is also discussed.展开更多
As for ultra-precision grinding of difficult-to-process thin-walled complex components with ball-end grinding wheels,interference is easy to occur.According to screw theory and grinding kinematics,a mathematical model...As for ultra-precision grinding of difficult-to-process thin-walled complex components with ball-end grinding wheels,interference is easy to occur.According to screw theory and grinding kinematics,a mathematical model is established to investigate the interference and grinding characteristics of the ball-end wheel.The relationship between grinding wheel inclination angle,C axis rotation angle,grinding position angle and grinding wheel wear are analyzed.As the grinding wheel inclination angle increases,the C axis rotatable range decreases and the grinding position angle increases.The grinding position angle and wheel radius wear show a negative correlation with the C axis rotation angle.Therefore,a trajectory planning criteria for increasing grinding speed as much as possible under the premise of avoiding interference is proposed to design the grinding trajectory.Then grinding point distribution on the ball-end wheel is calculated,and the grinding characteristics,grinding speed and maximum undeformed chip thickness,are investigated.Finally,a complex structural component can be ground without interference,and surface roughness and profile accuracy are improved to 40.2 nm and 0.399 lm,compared with 556 nm and 3.427 lm before ultra-precision grinding.The mathematical model can provide theoretical guidance for the analysis of interference and grinding characteristics in complex components grinding to improve its grinding quality.展开更多
A novel HBV integration site involved in hepatocarcinogenesis was investigated. The HBV DNA integration sites were detected by Alu-PCR in hepatocellular carcinoma tissues, matched surrounding liver tissues in 30 patie...A novel HBV integration site involved in hepatocarcinogenesis was investigated. The HBV DNA integration sites were detected by Alu-PCR in hepatocellular carcinoma tissues, matched surrounding liver tissues in 30 patients with hepatitis B-related hepatocellular carcinoma (HCC) and 3 cases of normal liver tissues. The integration sites and flanking sequences in human genome were sequenced and blasted, and the expression of integrated HBV genes was determined by reverse transcriptase-polymerase chain reaction (RT-PCR). The influence of the up-regulated expression of integrated genes on hepatocarcinogenesis was analyzed. Nineteen integration sites of HBV DNA into HCC tissues were obtained by RT-PCR and sequencing. These genes encoding proteins were: LOC51030, LOC157777, minichromosome maintenance complex component 3 associated protein (MCM3AP), MCTP1, SH3 and multiple ankyrin repeat domains 2 isoform 2, CCDC40, similar to HCG2033532, mitochondrial ribosomal S5 pseudogene 4. One of them was integrated into the intron of MCM3AP. RT-PCR demonstrated that the expression levels of MCM3AP mRNA in HCC tissues, matched surrounding liver tissues and normal liver tissues were in a descendent order. The ratio of MCM3AP mRNA to the GAPDH mRNA in these three tissues was 1.07375, 0.21573, 0.06747 respectively, with the difference being statistically significant among them (P<0.05). Meanwhile, the expression levels of MCM3AP mRNA from HCC tissues in which HBV DNA integrated into MCM3AP were still significantly higher than those without HBV DNA integrated into MCM3AP. It was concluded that the HBV DNA integration sites into human genome were random, and MCM3AP was a new site. The up-regulated MCM3AP mRNA may affect flanking sequences which promote the hepatocarcinogenesis.展开更多
The pressure and horizontal particle velocity combined descriptions in the very low frequency acoustic field of shallow wa- ter integrated with the concept of effective depth of Pekeris wave- guide is proposed, especi...The pressure and horizontal particle velocity combined descriptions in the very low frequency acoustic field of shallow wa- ter integrated with the concept of effective depth of Pekeris wave- guide is proposed, especially the active component of the pressure and horizontal particle velocity cross-spectrum, also called ho- rizontal complex cross acoustic intensity, when only two normal modes are trapped in the waveguide. Both the approximate theo- retic analysis and the numerical results show that the sign of the horizontal complex cross acoustic intensity active component is independent of the range when vertically deployed receiving dual sensors are placed in appropriate depths, the sum of which is equal to the waveguide effective depth, so it can be used to tell whether the sound source is near the surface or underwater; while the range rate is expected to be measured by utilizing the sign distribution characteristic of the reactive component. The further robustness analysis of the depth classification algorithm shows that the existence of shear waves in semi infinite basement and the change of acoustic velocity profiles have few effects on the application of this method, and the seabed attenuation will limit the detection range, but the algorithm still has a good robustness in the valid detection range.展开更多
On the one hand,the separation of thousands of compounds in a complex extract is thrilling,but may be still be separated unsatisfactorily.Hence,the question arises where to stop in high-sophisticated separation scienc...On the one hand,the separation of thousands of compounds in a complex extract is thrilling,but may be still be separated unsatisfactorily.Hence,the question arises where to stop in high-sophisticated separation science?Which technical effort is economically justifiable in routine?On the other hand,the separation itself does not imply an effect-directed answer to questions such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supported by the National Natural Science Foundation of China(Nos.52075255,92160301,52175415,52205475,and 92060203)。
文摘The aerospace community widely uses difficult-to-cut materials,such as titanium alloys,high-temperature alloys,metal/ceramic/polymer matrix composites,hard and brittle materials,and geometrically complex components,such as thin-walled structures,microchannels,and complex surfaces.Mechanical machining is the main material removal process for the vast majority of aerospace components.However,many problems exist,including severe and rapid tool wear,low machining efficiency,and poor surface integrity.Nontraditional energy-assisted mechanical machining is a hybrid process that uses nontraditional energies(vibration,laser,electricity,etc)to improve the machinability of local materials and decrease the burden of mechanical machining.This provides a feasible and promising method to improve the material removal rate and surface quality,reduce process forces,and prolong tool life.However,systematic reviews of this technology are lacking with respect to the current research status and development direction.This paper reviews the recent progress in the nontraditional energy-assisted mechanical machining of difficult-to-cut materials and components in the aerospace community.In addition,this paper focuses on the processing principles,material responses under nontraditional energy,resultant forces and temperatures,material removal mechanisms,and applications of these processes,including vibration-,laser-,electric-,magnetic-,chemical-,advanced coolant-,and hybrid nontraditional energy-assisted mechanical machining.Finally,a comprehensive summary of the principles,advantages,and limitations of each hybrid process is provided,and future perspectives on forward design,device development,and sustainability of nontraditional energy-assisted mechanical machining processes are discussed.
基金partially supported by the National Institutes of Health(R21CA185833 and R01GM113242 to H.S.)the National Natural Science Foundation of China(Nos.81660041 and 81260021 to L.D.)the Education Department of Jiangxi Province(GJJ150219to X.T.)
文摘The Mediator co-activator complex is a highly conserved,multisubunit protein complex required for gene transcription by RNA polymerase Ⅱ(RNAPⅡ)in all eukaryotes(Allen and Taatjes,2015).This complex,which consists of at least 30 polypeptides,can be divided into four structurally distinct sub-modules including the head,middle,tail,and cyclin-dependent kinase 8(CDK8)modules (CKM) (Fig. 1A) (Yin and Wang, 2014; Allen and Taatjes, 2015).
基金This work was financially supported by the Program of National Natural Science Foundation of China(Nos.U1937204 and 51905124)China Postdoctoral Science Foundation(2019M661278).
文摘Complex thin-walled titanium alloy components play a key role in the aircraft,aerospace and marine industries,offering the advantages of reduced weight and increased thermal resistance.The geometrical complexity,dimensional accuracy and in-service properties are essential to fulfill the high-performance standards required in new transportation systems,which brings new challenges to titanium alloy forming technologies.Traditional forming processes,such as superplastic forming or hot pressing,cannot meet all demands of modern applications due to their limited properties,low productivity and high cost.This has encouraged industry and research groups to develop novel high-efficiency forming processes.Hot gas pressure forming and hot stamping-quenching technologies have been developed for the manufacture of tubular and panel components,and are believed to be the cut-edge processes guaranteeing dimensional accuracy,microstructure and mechanical properties.This article intends to provide a critical review of high-efficiency titanium alloy forming processes,concentrating on latest investigations of controlling dimensional accuracy,microstructure and properties.The advantages and limitations of individual forming process are comprehensively analyzed,through which,future research trends of high-efficiency forming are identified including trends in process integration,processing window design,full cycle and multi-objective optimization.This review aims to provide a guide for researchers and process designers on the manufacture of thin-walled titanium alloy components whilst achieving high dimensional accuracy and satisfying performance properties with high efficiency and low cost.
文摘In this paper, the variability characteristics of the global field of sea surface temperature (SST) anomaly are studied by complex principal component (c.p.c.) analysis, whose results are also compared with those of real p.c. analysis. The data consist of 40 years of global SST monthly averages over latitudes from 42 5°S to 67 5°N. In the spatial domain, it is found that the distribution of the first complex loading amplitude is characterized by three areas of large values: the first one in the eastern and central equatorial Pacific Ocean, the second one in the northern tropical Indian Ocean and South China Sea, the third one in the northern Pacific Ocean. As it will be explained, this pattern may be considered as representative of El Nio mode. The first complex loading phase pattern shows a stationary wave in the Pacific (also revealed by real p.c. analysis) superimposed to an oscillating disturbance, propagating from the Pacific to Indian or the opposite way. A subsequent correlation analysis among different spatial points allows revealing disturbances actually propagating westward from the Pacific to the Indian Ocean, which could therefore represent reflected Rossby waves, i.e. the west phase of the signals that propagate disturbances of thermal structure in the tropical Pacific Ocean. In the time domain, a relation between the trend of the first complex principal component and the ENSO cycle is also established.
基金We deeply acknowledge Taif University for Supporting this research through Taif University Researchers Supporting Project number(TURSP-2020/231),Taif University,Taif,Saudi Arabia.
文摘Component-based software engineering is concerned with the develop-ment of software that can satisfy the customer prerequisites through reuse or inde-pendent development.Coupling and cohesion measurements are primarily used to analyse the better software design quality,increase the reliability and reduced system software complexity.The complexity measurement of cohesion and coupling component to analyze the relationship between the component module.In this paper,proposed the component selection framework of Hexa-oval optimization algorithm for selecting the suitable components from the repository.It measures the interface density modules of coupling and cohesion in a modular software sys-tem.This cohesion measurement has been taken into two parameters for analyz-ing the result of complexity,with the help of low cohesion and high cohesion.In coupling measures between the component of inside parameters and outside parameters.Thefinal process of coupling and cohesion,the measured values were used for the average calculation of components parameter.This paper measures the complexity of direct and indirect interaction among the component as well as the proposed algorithm selecting the optimal component for the repository.The better result is observed for high cohesion and low coupling in compo-nent-based software engineering.
基金supported by the National Natural Science Foundation of China(Nos.51921003,92160301,52175415 and 52205475)the Science Center for Gas Turbine Project(No.P2022-A-IV-002-001)Natural Science Foundation of Jiangsu Province(No.BK20210295).
文摘Presently,the service performance of new-generation high-tech equipment is directly affected by the manufacturing quality of complex thin-walled components.A high-efficiency and quality manufacturing of these complex thin-walled components creates a bottleneck that needs to be solved urgently in machinery manufacturing.To address this problem,the collaborative manufacturing of structure shape and surface integrity has emerged as a new process that can shorten processing cycles,improve machining qualities,and reduce costs.This paper summarises the research status on the material removal mechanism,precision control of structure shape,machined surface integrity control and intelligent process control technology of complex thin-walled components.Numerous solutions and technical approaches are then put forward to solve the critical problems in the high-performance manufacturing of complex thin-wall components.The development status,challenge and tendency of collaborative manufacturing technologies in the high-efficiency and quality manufacturing of complex thin-wall components is also discussed.
基金the National Key Research and Development Program of China(No.2018YFB 1107600)。
文摘As for ultra-precision grinding of difficult-to-process thin-walled complex components with ball-end grinding wheels,interference is easy to occur.According to screw theory and grinding kinematics,a mathematical model is established to investigate the interference and grinding characteristics of the ball-end wheel.The relationship between grinding wheel inclination angle,C axis rotation angle,grinding position angle and grinding wheel wear are analyzed.As the grinding wheel inclination angle increases,the C axis rotatable range decreases and the grinding position angle increases.The grinding position angle and wheel radius wear show a negative correlation with the C axis rotation angle.Therefore,a trajectory planning criteria for increasing grinding speed as much as possible under the premise of avoiding interference is proposed to design the grinding trajectory.Then grinding point distribution on the ball-end wheel is calculated,and the grinding characteristics,grinding speed and maximum undeformed chip thickness,are investigated.Finally,a complex structural component can be ground without interference,and surface roughness and profile accuracy are improved to 40.2 nm and 0.399 lm,compared with 556 nm and 3.427 lm before ultra-precision grinding.The mathematical model can provide theoretical guidance for the analysis of interference and grinding characteristics in complex components grinding to improve its grinding quality.
基金supported by grants from the National Natural Sciences Foundation of China (No. 30872237)the National Program on Key Basic Research Project (973 Program) (No. 2007CB512900)
文摘A novel HBV integration site involved in hepatocarcinogenesis was investigated. The HBV DNA integration sites were detected by Alu-PCR in hepatocellular carcinoma tissues, matched surrounding liver tissues in 30 patients with hepatitis B-related hepatocellular carcinoma (HCC) and 3 cases of normal liver tissues. The integration sites and flanking sequences in human genome were sequenced and blasted, and the expression of integrated HBV genes was determined by reverse transcriptase-polymerase chain reaction (RT-PCR). The influence of the up-regulated expression of integrated genes on hepatocarcinogenesis was analyzed. Nineteen integration sites of HBV DNA into HCC tissues were obtained by RT-PCR and sequencing. These genes encoding proteins were: LOC51030, LOC157777, minichromosome maintenance complex component 3 associated protein (MCM3AP), MCTP1, SH3 and multiple ankyrin repeat domains 2 isoform 2, CCDC40, similar to HCG2033532, mitochondrial ribosomal S5 pseudogene 4. One of them was integrated into the intron of MCM3AP. RT-PCR demonstrated that the expression levels of MCM3AP mRNA in HCC tissues, matched surrounding liver tissues and normal liver tissues were in a descendent order. The ratio of MCM3AP mRNA to the GAPDH mRNA in these three tissues was 1.07375, 0.21573, 0.06747 respectively, with the difference being statistically significant among them (P<0.05). Meanwhile, the expression levels of MCM3AP mRNA from HCC tissues in which HBV DNA integrated into MCM3AP were still significantly higher than those without HBV DNA integrated into MCM3AP. It was concluded that the HBV DNA integration sites into human genome were random, and MCM3AP was a new site. The up-regulated MCM3AP mRNA may affect flanking sequences which promote the hepatocarcinogenesis.
基金supported by the National Natural Science Foundation of China(1140440611374072)
文摘The pressure and horizontal particle velocity combined descriptions in the very low frequency acoustic field of shallow wa- ter integrated with the concept of effective depth of Pekeris wave- guide is proposed, especially the active component of the pressure and horizontal particle velocity cross-spectrum, also called ho- rizontal complex cross acoustic intensity, when only two normal modes are trapped in the waveguide. Both the approximate theo- retic analysis and the numerical results show that the sign of the horizontal complex cross acoustic intensity active component is independent of the range when vertically deployed receiving dual sensors are placed in appropriate depths, the sum of which is equal to the waveguide effective depth, so it can be used to tell whether the sound source is near the surface or underwater; while the range rate is expected to be measured by utilizing the sign distribution characteristic of the reactive component. The further robustness analysis of the depth classification algorithm shows that the existence of shear waves in semi infinite basement and the change of acoustic velocity profiles have few effects on the application of this method, and the seabed attenuation will limit the detection range, but the algorithm still has a good robustness in the valid detection range.
文摘On the one hand,the separation of thousands of compounds in a complex extract is thrilling,but may be still be separated unsatisfactorily.Hence,the question arises where to stop in high-sophisticated separation science?Which technical effort is economically justifiable in routine?On the other hand,the separation itself does not imply an effect-directed answer to questions such