TiAl-based alloys sheet with thickness of 0.3-0.4 mm as well as dimension of 150 mm×100 mm was fabricated successfully by using electron beam-physical vapor deposition(EB-PVD) method. The microscopic morphology a...TiAl-based alloys sheet with thickness of 0.3-0.4 mm as well as dimension of 150 mm×100 mm was fabricated successfully by using electron beam-physical vapor deposition(EB-PVD) method. The microscopic morphology and phase composition of specimens in various states were analyzed by atomic force microscope(AFM), scanning electron microscope(SEM) and X-ray diffractometer(XRD), respectively. The results indicate that the as-deposited TiAl-based alloys sheet has good surface quality and is composed of γ, α2 and τ phase. There is natural delamination inside the sheet, of which the microstructure is columnar crystal, and the component shows a gradient change along the normal direction of substrate. After the vacuum hot pressing treatment and subsequent homogenization treatment, the columnar crystal transforms into the coarse fully lamellar microstructure, the delamination phenomenon and τ phase disappear, α2 phase decreases obviously, and the composition tends to uniformization.展开更多
This scientific paper is a comparative analysis of two mathematical conjectures. The newly proposed -3(-n) - 1 Remer conjecture and how it is related to and a proof of the more well known 3n + 1 Collatz conjecture. An...This scientific paper is a comparative analysis of two mathematical conjectures. The newly proposed -3(-n) - 1 Remer conjecture and how it is related to and a proof of the more well known 3n + 1 Collatz conjecture. An overview of both conjectures and their respective iterative processes will be presented. Showcasing their unique properties and behavior to each other. Through a detailed comparison, we highlight the similarities and differences between these two conjectures and discuss their significance in the field of mathematics. And how they prove each other to be true.展开更多
A methodology is proposed to enable real-time evaluation of the observability of local motions,and generate a local observability cost map to enable informed local motion planning in order to avoid potential degradati...A methodology is proposed to enable real-time evaluation of the observability of local motions,and generate a local observability cost map to enable informed local motion planning in order to avoid potential degradation or degeneracy in state estimator performance.The proposed approach leverages efficient numerical techniques in nonlinear observability analysis and motion primitive-based planning technique to realize the local observability prediction with real-time performance.The degradation of the state estimation performance can be readily predicted with the local observability evaluation result.The proposed approach is specialized to a representative optimization-based monocular visual-inertial state estimation formulation and evaluated through simulation and experiments.The experimental results demonstrated the ability of the proposed methodology to correctly anticipate the potential state estimation degradation.展开更多
For precise plastic deformation,microstructure control is essential especially for β-solidifying γ-TiAl alloy with duplex structure.Based on stereology,the microstructure of isothermally compressed γ-TiAl alloy was...For precise plastic deformation,microstructure control is essential especially for β-solidifying γ-TiAl alloy with duplex structure.Based on stereology,the microstructure of isothermally compressed γ-TiAl alloy was divided into β_(0) grains,remnant α_(2)/γ lamellar colonies,α_(2) and γ grains.The results show that the volume fraction of β_(0) grains slightly increases in the isothermally compressed γ-TiAl alloy with the increase of height reduction.Meanwhile,the volume fractions of remnant α_(2)/γ lamellar colonies and α_(2) grains decrease.However,the volume fraction of γ grains increases from 64.39% to 78.47%.According to the quantitative results,the α→γ phase transformation was investigated in-depth,and it is found that isothermal compression accelerates the α→γ phase transformation.The first α→γ phase transformation is similar to ledge-controlled transformation,through which remnant α_(2)/γ lamellar colonies finally convert intoγgrains in isothermal compression.The second is achieved by α/γ phase interface immigration.展开更多
针对长江中下游稻区不同粳稻品种,以不同纬度多个地点的860份稻米样本为材料,基于11项食味品质指标,运用主成分分析、多元线性回归、偏最小二乘法、判别分析、分类回归树(classification and regression free,CART)决策树与反向传播(bac...针对长江中下游稻区不同粳稻品种,以不同纬度多个地点的860份稻米样本为材料,基于11项食味品质指标,运用主成分分析、多元线性回归、偏最小二乘法、判别分析、分类回归树(classification and regression free,CART)决策树与反向传播(back propagation,BP)神经网络分别建立稻米食味品质等级预测模型,通过验证模型的准确性与稳定性,筛选出适合稻米食味品质综合评价的方法或模型。结果表明:BP神经网络模型的2次验证准确度与稳定性均最高,预测准确率分别为92.68%与92.31%;偏最小二乘法模型的2次预测准确率均在80%以上(分别为80.49%、87.18%),但2次验证结果相差较大(6.69%);判别分析与多元线性回归模型的平均预测准确率相近(分别为80.12%、78.77%),但判别分析模型的稳定性优于多元线性回归模型;主成分分析模型的平均预测准确率最低(67.32%),且2次验证结果差异也较大(8.94%);CART决策树模型的稳定性最差,2次验证准确率分别为53.66%与89.74%,相差达36.08%。因此,利用BP神经网络模型预测稻米食味品质等级具有较高的准确性与稳定性,可为长江中下游稻区稻米食味品质综合评价与优质食味水稻品种的筛选提供理论与方法支持。展开更多
基金Project(90405016) supported by the National Natural Science Foundation of China
文摘TiAl-based alloys sheet with thickness of 0.3-0.4 mm as well as dimension of 150 mm×100 mm was fabricated successfully by using electron beam-physical vapor deposition(EB-PVD) method. The microscopic morphology and phase composition of specimens in various states were analyzed by atomic force microscope(AFM), scanning electron microscope(SEM) and X-ray diffractometer(XRD), respectively. The results indicate that the as-deposited TiAl-based alloys sheet has good surface quality and is composed of γ, α2 and τ phase. There is natural delamination inside the sheet, of which the microstructure is columnar crystal, and the component shows a gradient change along the normal direction of substrate. After the vacuum hot pressing treatment and subsequent homogenization treatment, the columnar crystal transforms into the coarse fully lamellar microstructure, the delamination phenomenon and τ phase disappear, α2 phase decreases obviously, and the composition tends to uniformization.
文摘This scientific paper is a comparative analysis of two mathematical conjectures. The newly proposed -3(-n) - 1 Remer conjecture and how it is related to and a proof of the more well known 3n + 1 Collatz conjecture. An overview of both conjectures and their respective iterative processes will be presented. Showcasing their unique properties and behavior to each other. Through a detailed comparison, we highlight the similarities and differences between these two conjectures and discuss their significance in the field of mathematics. And how they prove each other to be true.
文摘A methodology is proposed to enable real-time evaluation of the observability of local motions,and generate a local observability cost map to enable informed local motion planning in order to avoid potential degradation or degeneracy in state estimator performance.The proposed approach leverages efficient numerical techniques in nonlinear observability analysis and motion primitive-based planning technique to realize the local observability prediction with real-time performance.The degradation of the state estimation performance can be readily predicted with the local observability evaluation result.The proposed approach is specialized to a representative optimization-based monocular visual-inertial state estimation formulation and evaluated through simulation and experiments.The experimental results demonstrated the ability of the proposed methodology to correctly anticipate the potential state estimation degradation.
基金the financial supports from the National Natural Science Foundation of China(No.51975478)the Fundamental Research Funds for the Central Universities,China(No.3102019MS0403).
文摘For precise plastic deformation,microstructure control is essential especially for β-solidifying γ-TiAl alloy with duplex structure.Based on stereology,the microstructure of isothermally compressed γ-TiAl alloy was divided into β_(0) grains,remnant α_(2)/γ lamellar colonies,α_(2) and γ grains.The results show that the volume fraction of β_(0) grains slightly increases in the isothermally compressed γ-TiAl alloy with the increase of height reduction.Meanwhile,the volume fractions of remnant α_(2)/γ lamellar colonies and α_(2) grains decrease.However,the volume fraction of γ grains increases from 64.39% to 78.47%.According to the quantitative results,the α→γ phase transformation was investigated in-depth,and it is found that isothermal compression accelerates the α→γ phase transformation.The first α→γ phase transformation is similar to ledge-controlled transformation,through which remnant α_(2)/γ lamellar colonies finally convert intoγgrains in isothermal compression.The second is achieved by α/γ phase interface immigration.
文摘针对长江中下游稻区不同粳稻品种,以不同纬度多个地点的860份稻米样本为材料,基于11项食味品质指标,运用主成分分析、多元线性回归、偏最小二乘法、判别分析、分类回归树(classification and regression free,CART)决策树与反向传播(back propagation,BP)神经网络分别建立稻米食味品质等级预测模型,通过验证模型的准确性与稳定性,筛选出适合稻米食味品质综合评价的方法或模型。结果表明:BP神经网络模型的2次验证准确度与稳定性均最高,预测准确率分别为92.68%与92.31%;偏最小二乘法模型的2次预测准确率均在80%以上(分别为80.49%、87.18%),但2次验证结果相差较大(6.69%);判别分析与多元线性回归模型的平均预测准确率相近(分别为80.12%、78.77%),但判别分析模型的稳定性优于多元线性回归模型;主成分分析模型的平均预测准确率最低(67.32%),且2次验证结果差异也较大(8.94%);CART决策树模型的稳定性最差,2次验证准确率分别为53.66%与89.74%,相差达36.08%。因此,利用BP神经网络模型预测稻米食味品质等级具有较高的准确性与稳定性,可为长江中下游稻区稻米食味品质综合评价与优质食味水稻品种的筛选提供理论与方法支持。
