Cell wall architecture plays a key role in stalk strength and forage digestibility.Lignin,cellulose,and hemicellulose are the three main components of plant cell walls,and they can impact stalk quality by affecting th...Cell wall architecture plays a key role in stalk strength and forage digestibility.Lignin,cellulose,and hemicellulose are the three main components of plant cell walls,and they can impact stalk quality by affecting the structure and strength of the cell wall.To explore cell wall development during secondary cell wall lignification in maize stalks,conventional and conditional genetic mapping were used to identify the dynamic quantitative trait loci(QTLs)of the cell wall components and digestibility traits during five growth stages after silking.Acid detergent lignin(ADL),cellulose(CEL),acid detergent fiber(ADF),neutral detergent fiber(NDF),and in vitro dry matter digestibility(IVDMD)were evaluated in a maize recombinant inbred line(RIL)population.ADL,CEL,ADF,and NDF gradually increased from 10 to 40 days after silking(DAS),and then they decreased.IVDMD initially decreased until 40 DAS,and then it increased slightly.Seventytwo QTLs were identified for the five traits,and each accounted for 3.48–24.04%of the phenotypic variation.Six QTL hotspots were found,and they were localized in the 1.08,2.04,2.07,7.03,8.05,and 9.03 bins of the maize genome.Within the interval of the pleiotropic QTL identified in bin 1.08 of the maize genome,six genes associated with cell wall component biosynthesis were identified as potential candidate genes for stalk strength as well as cell wall-related traits.In addition,26 conditional QTLs were detected in the five stages for all of the investigated traits.Twenty-two of the 26 conditional QTLs were found at 30 DAS conditioned using the values of 20 DAS,and at 50 DAS conditioned using the values of 40 DAS.These results indicated that cell wall-related traits are regulated by many genes,which are specifically expressed at different stages after silking.Simultaneous improvements in both forage digestibility and lodging resistance could be achieved by pyramiding multiple beneficial QTL alleles identified in this study.展开更多
Counter gravity casting equipments(CGCE) were widely used to produce large thin-walled A357 aluminum alloy components. To improve the pressure control precision of CGCE to get high quality castings, a pressure control...Counter gravity casting equipments(CGCE) were widely used to produce large thin-walled A357 aluminum alloy components. To improve the pressure control precision of CGCE to get high quality castings, a pressure control system based on fuzzy-PID hybrid control technology and the digital assembled valve was developed. The actual pressure tracking experiment results show that the special system by applying PID controller and fuzzy controller to varied phases, is not only able to inherit the small error and good static stability of classical PID control, but also has fuzzy control’s advantage of fully adapting itself to the object. The pressure control error is less than 0.3 kPa. By using this pressure control system, large complex thin-walled A357 aluminum alloy castings with high quality was successfully produced.展开更多
The deformation performance index limits of high reinforced concrete(RC) shear wall components based on Chinese codes were discussed by the nonlinear finite element method.Two typical RC shear wall specimens in the pr...The deformation performance index limits of high reinforced concrete(RC) shear wall components based on Chinese codes were discussed by the nonlinear finite element method.Two typical RC shear wall specimens in the previous work were first used to verify the correctness of the nonlinear finite element method.Then,the nonlinear finite element method was applied to study the deformability of a set of high RC shear wall components designed according to current Chinese codes and with shear span ratio λ≥2.0.Parametric studies were made on the influence of shear span ratio,axial compression ratio,ratio of flexural capacity to shear capacity and main flexural reinforcement ratio of confined boundary members.Finally,the deformation performance index and its limits of high RC shear wall components under severe earthquakes were proposed by the finite element model results,which offers a reference in determining the performance status of RC shear wall components designed based on Chinese codes.展开更多
Thin-walled structures have been widely used in the aerospace industry.The dynamic interaction between the milling cutter and thin-walled workpiece can easily lead to vibration.This paper investigates the vibration ca...Thin-walled structures have been widely used in the aerospace industry.The dynamic interaction between the milling cutter and thin-walled workpiece can easily lead to vibration.This paper investigates the vibration caused during milling the thin-walled workpiece on the NC machining center,presents a theoretical milling vibration model of thin-walled beam.The model was verified by using milling experiments and numerical simulations.Some valuable conclusions are derived,this will be references to scientific research and guides to the vibration-free milling of thin-walled structures at different cutting speeds.展开更多
We investigate domain wall excitations in a two-component Bose–Einstein condensate with two-body interactions and pair-transition effects. It is shown that domain wall excitations can be described exactly by kink and...We investigate domain wall excitations in a two-component Bose–Einstein condensate with two-body interactions and pair-transition effects. It is shown that domain wall excitations can be described exactly by kink and anti-kink excitations in each component. The domain wall solutions are given analytically, which exist with different conditions compared with the domain wall reported before. Bubble-droplet structure can be also obtained from the fundamental domain wall, and their interactions are investigated analytically. Especially, domain wall interactions demonstrate some striking particle transition dynamics. These striking transition effects make the domain wall admit quite different collision behavior, in contrast to the collision between solitons or other nonlinear waves. The collisions between kinks induce some phase shift, which makes the domain wall change greatly. Their collisions can be elastic or inelastic with proper combination of fundamental domain walls. These characters can be used to manipulate one domain wall by interacting with other ones.展开更多
Fixture locating layout has a direct and influential impact on aeronautical thin-walled component(ATWC)manufacturing quality.The purpose is to develop a topological optimization method for ATWC fixture locating layout...Fixture locating layout has a direct and influential impact on aeronautical thin-walled component(ATWC)manufacturing quality.The purpose is to develop a topological optimization method for ATWC fixture locating layout to minimize the manufacturing deformation.Firstly,a topological optimization model that takes the stiffness of ATWC as the objective function and the volume of the locating structure as the constraint is established.Secondly,ATWC and the locating structure are regarded as an integrated entity,and the variable-density method based topological optimization approach is adopted for the optimization of the locating structure using ABAQUS topology optimization module(ATOM).Thirdly,through a subsequent model reconstruction referring to the obtained topological structure,the optimal fixture locating layout is achieved.Finally,a case study is conducted to verify the proposed method and the comparison results with firefly algorithm(FA)coupled with finite element analysis(FEA)indicate that the number and positions of the locators for ATWC can be optimized simultaneously and successfully by the proposed topological optimization model.展开更多
The microstructure and tensile properties were investigated in a thick-walled section (approximately 45 mm×43 mm) of a rheocast component produced by the RheoMetalTM process.Due to the long solidification period ...The microstructure and tensile properties were investigated in a thick-walled section (approximately 45 mm×43 mm) of a rheocast component produced by the RheoMetalTM process.Due to the long solidification period of such components, it is expected that the Al-Si eutectic formed will be coarse.Therefore, sodium (Na) was used as a modifying agent to reduce the coarseness of the eutectic.Tensile test bars were machined from three different sets of materials:1) non-modified melt, 2) modified melt cast directly after Na addition, and 3) modified melt cast 30 min after Na addition.The alloy used was a secondary AlSi6Cu2.5 alloy (STENAL Rheo1), specially developed for rheocasting.The material was studied in the as-cast condition as well as after a T6 heat treatment.The results show that the Al-Si eutectic is significantly refined by the Na addition, even after a fading time of 30 min.However, it is observed that the Na modification generally has a detrimental effect on the mechanical properties, despite the structure refinement.This is especially true in the T6 heat treated condition, where the yield strength is reduced by more than 30%.Some possible mechanisms for the degradation of mechanical performance are discussed.展开更多
目的:为实现从母体腹壁混合信号中提取高信噪比和波形清晰的胎儿心电信号,提出一种融合核主成分分析(kernel principal component analysis,KPCA)、快速独立成分分析(fast independent component analysis,FastICA)及奇异值分解(singula...目的:为实现从母体腹壁混合信号中提取高信噪比和波形清晰的胎儿心电信号,提出一种融合核主成分分析(kernel principal component analysis,KPCA)、快速独立成分分析(fast independent component analysis,FastICA)及奇异值分解(singular value decomposition,SVD)的胎儿心电信号提取算法。方法:首先,采用KPCA对母体心电信号进行降维,再利用改进的基于负熵的FastICA处理降维后的数据,得到独立成分。随后,引入样本熵进行信号通道选择,挑选出包含最多母体信息的信号通道。在选中的母体通道上进行SVD,得到母体心电信号的近似估计,再用腹壁源信号减去该信号得到胎儿心电的初步估计。最后,采用改进的基于负熵的FastICA成功分离出纯净的胎儿心电信号。在腹部和直接胎儿心电图数据库(Abdominal and Direct Fetal Electrocardiogram Database,ADFECGDB)和PhysioNet 2013挑战赛数据库中对提出的算法进行验证。结果:提出的算法在主观视觉效果和客观评价指标上都表现出优越的性能。在ADFECGDB数据库中,胎儿QRS复合波检测的敏感度、阳性预测值和F1值分别为99.74%、98.85%和99.30%;在PhysioNet 2013挑战赛数据库中,胎儿QRS复合波检测的敏感度、阳性预测值和F1值分别为99.10%、97.87%和98.48%。结论:融合KPCA、FastICA及SVD的胎儿心电信号提取算法在提取胎儿心电信号的同时有效处理了附加噪声,为胎儿疾病的早期诊断提供了有力支持。展开更多
Cell walls in plants,particularly forest trees,are the major carbon sink of the terrestrial ecosystem.Chemical and biosynthetic features of plant cell walls were revealed early on,focusing mostly on herbaceous model s...Cell walls in plants,particularly forest trees,are the major carbon sink of the terrestrial ecosystem.Chemical and biosynthetic features of plant cell walls were revealed early on,focusing mostly on herbaceous model species.Recent developments in genomics,transcriptomics,epigenomics,transgenesis,and associated analytical techniques are enabling novel insights into formation of woody cell walls.Here,we review multilevel regulation of cell wall biosynthesis in forest tree species.We highlight current approaches to engineering cell walls as potential feedstock for materials and energy and survey reported field tests of such engineered transgenic trees.We outline opportunities and challenges in future research to better understand cell type biogenesis for more efficient wood cell wall modification and utilization for biomaterials or for enhanced carbon capture and storage.展开更多
基金the National Natural Science Foundation of China(31801367)the National Key Research and Development Program of China(2016YFD0101200)the Agricultural Science and Technology Innovation Program of Chinese Academy of Agricultural Sciences.
文摘Cell wall architecture plays a key role in stalk strength and forage digestibility.Lignin,cellulose,and hemicellulose are the three main components of plant cell walls,and they can impact stalk quality by affecting the structure and strength of the cell wall.To explore cell wall development during secondary cell wall lignification in maize stalks,conventional and conditional genetic mapping were used to identify the dynamic quantitative trait loci(QTLs)of the cell wall components and digestibility traits during five growth stages after silking.Acid detergent lignin(ADL),cellulose(CEL),acid detergent fiber(ADF),neutral detergent fiber(NDF),and in vitro dry matter digestibility(IVDMD)were evaluated in a maize recombinant inbred line(RIL)population.ADL,CEL,ADF,and NDF gradually increased from 10 to 40 days after silking(DAS),and then they decreased.IVDMD initially decreased until 40 DAS,and then it increased slightly.Seventytwo QTLs were identified for the five traits,and each accounted for 3.48–24.04%of the phenotypic variation.Six QTL hotspots were found,and they were localized in the 1.08,2.04,2.07,7.03,8.05,and 9.03 bins of the maize genome.Within the interval of the pleiotropic QTL identified in bin 1.08 of the maize genome,six genes associated with cell wall component biosynthesis were identified as potential candidate genes for stalk strength as well as cell wall-related traits.In addition,26 conditional QTLs were detected in the five stages for all of the investigated traits.Twenty-two of the 26 conditional QTLs were found at 30 DAS conditioned using the values of 20 DAS,and at 50 DAS conditioned using the values of 40 DAS.These results indicated that cell wall-related traits are regulated by many genes,which are specifically expressed at different stages after silking.Simultaneous improvements in both forage digestibility and lodging resistance could be achieved by pyramiding multiple beneficial QTL alleles identified in this study.
基金Project(2006CB605202) supported by the Basic Research Development Program of China
文摘Counter gravity casting equipments(CGCE) were widely used to produce large thin-walled A357 aluminum alloy components. To improve the pressure control precision of CGCE to get high quality castings, a pressure control system based on fuzzy-PID hybrid control technology and the digital assembled valve was developed. The actual pressure tracking experiment results show that the special system by applying PID controller and fuzzy controller to varied phases, is not only able to inherit the small error and good static stability of classical PID control, but also has fuzzy control’s advantage of fully adapting itself to the object. The pressure control error is less than 0.3 kPa. By using this pressure control system, large complex thin-walled A357 aluminum alloy castings with high quality was successfully produced.
基金Project(2009ZA04) supported by the Independent Research Foundation of State Key Laboratory of Subtropical Architecture Science,China
文摘The deformation performance index limits of high reinforced concrete(RC) shear wall components based on Chinese codes were discussed by the nonlinear finite element method.Two typical RC shear wall specimens in the previous work were first used to verify the correctness of the nonlinear finite element method.Then,the nonlinear finite element method was applied to study the deformability of a set of high RC shear wall components designed according to current Chinese codes and with shear span ratio λ≥2.0.Parametric studies were made on the influence of shear span ratio,axial compression ratio,ratio of flexural capacity to shear capacity and main flexural reinforcement ratio of confined boundary members.Finally,the deformation performance index and its limits of high RC shear wall components under severe earthquakes were proposed by the finite element model results,which offers a reference in determining the performance status of RC shear wall components designed based on Chinese codes.
文摘Thin-walled structures have been widely used in the aerospace industry.The dynamic interaction between the milling cutter and thin-walled workpiece can easily lead to vibration.This paper investigates the vibration caused during milling the thin-walled workpiece on the NC machining center,presents a theoretical milling vibration model of thin-walled beam.The model was verified by using milling experiments and numerical simulations.Some valuable conclusions are derived,this will be references to scientific research and guides to the vibration-free milling of thin-walled structures at different cutting speeds.
基金Project supported by the National Natural Science Foundation of China(Grant No.11775176)the Major Basic Research Program of the Natural Science Foundation of Shaanxi Province,China(Grant No.2018KJXX-094)the Key Innovative Research Team of Quantum Many-Body Theory and Quantum Control in Shaanxi Province,China(Grant No.2017KCT-12)
文摘We investigate domain wall excitations in a two-component Bose–Einstein condensate with two-body interactions and pair-transition effects. It is shown that domain wall excitations can be described exactly by kink and anti-kink excitations in each component. The domain wall solutions are given analytically, which exist with different conditions compared with the domain wall reported before. Bubble-droplet structure can be also obtained from the fundamental domain wall, and their interactions are investigated analytically. Especially, domain wall interactions demonstrate some striking particle transition dynamics. These striking transition effects make the domain wall admit quite different collision behavior, in contrast to the collision between solitons or other nonlinear waves. The collisions between kinks induce some phase shift, which makes the domain wall change greatly. Their collisions can be elastic or inelastic with proper combination of fundamental domain walls. These characters can be used to manipulate one domain wall by interacting with other ones.
基金supported by the National Natural Science Foundation of China(No.51375396)the Shaanxi Science and Technology Innovation Project Plan,China(No.2016KTCQ01-50)
文摘Fixture locating layout has a direct and influential impact on aeronautical thin-walled component(ATWC)manufacturing quality.The purpose is to develop a topological optimization method for ATWC fixture locating layout to minimize the manufacturing deformation.Firstly,a topological optimization model that takes the stiffness of ATWC as the objective function and the volume of the locating structure as the constraint is established.Secondly,ATWC and the locating structure are regarded as an integrated entity,and the variable-density method based topological optimization approach is adopted for the optimization of the locating structure using ABAQUS topology optimization module(ATOM).Thirdly,through a subsequent model reconstruction referring to the obtained topological structure,the optimal fixture locating layout is achieved.Finally,a case study is conducted to verify the proposed method and the comparison results with firefly algorithm(FA)coupled with finite element analysis(FEA)indicate that the number and positions of the locators for ATWC can be optimized simultaneously and successfully by the proposed topological optimization model.
文摘The microstructure and tensile properties were investigated in a thick-walled section (approximately 45 mm×43 mm) of a rheocast component produced by the RheoMetalTM process.Due to the long solidification period of such components, it is expected that the Al-Si eutectic formed will be coarse.Therefore, sodium (Na) was used as a modifying agent to reduce the coarseness of the eutectic.Tensile test bars were machined from three different sets of materials:1) non-modified melt, 2) modified melt cast directly after Na addition, and 3) modified melt cast 30 min after Na addition.The alloy used was a secondary AlSi6Cu2.5 alloy (STENAL Rheo1), specially developed for rheocasting.The material was studied in the as-cast condition as well as after a T6 heat treatment.The results show that the Al-Si eutectic is significantly refined by the Na addition, even after a fading time of 30 min.However, it is observed that the Na modification generally has a detrimental effect on the mechanical properties, despite the structure refinement.This is especially true in the T6 heat treated condition, where the yield strength is reduced by more than 30%.Some possible mechanisms for the degradation of mechanical performance are discussed.
文摘目的:为实现从母体腹壁混合信号中提取高信噪比和波形清晰的胎儿心电信号,提出一种融合核主成分分析(kernel principal component analysis,KPCA)、快速独立成分分析(fast independent component analysis,FastICA)及奇异值分解(singular value decomposition,SVD)的胎儿心电信号提取算法。方法:首先,采用KPCA对母体心电信号进行降维,再利用改进的基于负熵的FastICA处理降维后的数据,得到独立成分。随后,引入样本熵进行信号通道选择,挑选出包含最多母体信息的信号通道。在选中的母体通道上进行SVD,得到母体心电信号的近似估计,再用腹壁源信号减去该信号得到胎儿心电的初步估计。最后,采用改进的基于负熵的FastICA成功分离出纯净的胎儿心电信号。在腹部和直接胎儿心电图数据库(Abdominal and Direct Fetal Electrocardiogram Database,ADFECGDB)和PhysioNet 2013挑战赛数据库中对提出的算法进行验证。结果:提出的算法在主观视觉效果和客观评价指标上都表现出优越的性能。在ADFECGDB数据库中,胎儿QRS复合波检测的敏感度、阳性预测值和F1值分别为99.74%、98.85%和99.30%;在PhysioNet 2013挑战赛数据库中,胎儿QRS复合波检测的敏感度、阳性预测值和F1值分别为99.10%、97.87%和98.48%。结论:融合KPCA、FastICA及SVD的胎儿心电信号提取算法在提取胎儿心电信号的同时有效处理了附加噪声,为胎儿疾病的早期诊断提供了有力支持。
基金supported by the National Key Research and Development Program of China(2021YFD2200700)the Fundamental Research Funds for the Central Universities of China(grant 2572022DQ01)+6 种基金the Heilongjiang Touyan Innovation Team Program(Tree Genetics and Breeding Innovation Team)the 111 Project(B16010)supported by the Young Scholar Fellowship Columbus Program from the Ministry of Science and Technology of Taiwan,China(111-2311-B-002-021)the National Science and Technology Council(112-2636-B-006-006)MEXT KAKENHI(JP18H05484,JP18H05489)the Research Foundation Flanders for proving the predoctoral fellowship.D.M.O.is indebted to the Research Foundation Flanders(FWO,grant 1246123N)for a postdoctoral fellowshipsupported by the Energy Transition Fund projects AdLibio and AdvBio,the interuniversity iBOF project NextBioRef,and the FWO project G011620N。
文摘Cell walls in plants,particularly forest trees,are the major carbon sink of the terrestrial ecosystem.Chemical and biosynthetic features of plant cell walls were revealed early on,focusing mostly on herbaceous model species.Recent developments in genomics,transcriptomics,epigenomics,transgenesis,and associated analytical techniques are enabling novel insights into formation of woody cell walls.Here,we review multilevel regulation of cell wall biosynthesis in forest tree species.We highlight current approaches to engineering cell walls as potential feedstock for materials and energy and survey reported field tests of such engineered transgenic trees.We outline opportunities and challenges in future research to better understand cell type biogenesis for more efficient wood cell wall modification and utilization for biomaterials or for enhanced carbon capture and storage.