Artificial intelligence(AI),which has recently gained popularity,is being extensively employed in modern fault diagnostic research to preserve the reliability and productivity of machines.The effectiveness of AI is in...Artificial intelligence(AI),which has recently gained popularity,is being extensively employed in modern fault diagnostic research to preserve the reliability and productivity of machines.The effectiveness of AI is influenced by the quality of the labeled training data.However,in engineering scenarios,available data on mechanical equipment are scarce,and collecting massive amounts of well-annotated fault data to train AI models is expensive and difficult.In response to the inadequacy of training samples,a numerical simulation-based partial transfer learning method for machinery fault diagnosis is proposed.First,a suitable simulation model of critical components in a mechanical system is developed using the finite element method(FEM),and numerical simulation is performed to acquire FEM simulation samples containing different fault types.Second,several synthetic simulation samples are generated to form complete source domain training samples using a generative adversarial network.Subsequently,the partial transfer learning network is trained to extract shared fault characteristics between the simulation and measured samples in the case of class imbalance.Finally,the resulting model is used to diagnose unknown samples from real-world mechanical systems in operation.The proposed method is tested on actual fault samples of bearings and gears obtained from a public dataset and experimental test rig available in our laboratory,achieving average classification accuracy of 99.54%and 99.64%,respectively.Comparison investigations reveal that the proposed method has superior classification and generalization ability when detecting faults in real mechanical systems.展开更多
Monte Carlo method was applied to simulate the oscillatory behavior during partial oxidation of methane under non-isothermal condition. The simulation was performed to examine the influences of heat transfer constant ...Monte Carlo method was applied to simulate the oscillatory behavior during partial oxidation of methane under non-isothermal condition. The simulation was performed to examine the influences of heat transfer constant and particle size on the kinetic oscillation. The oscillatory period and amplitude were observed to increase with the increase of heat transfer constant. The increase of catalyst particle size was found to result in short oscillatory period and more or less regular oscillations combined with the formation of oxide down to L = 100.展开更多
The flow and heat transfer of an electrically conducting non-Newtonian second grade fluid due to a radially stretching surface with partial slip is considered. The partial slip is controlled by a dimensionless slip fa...The flow and heat transfer of an electrically conducting non-Newtonian second grade fluid due to a radially stretching surface with partial slip is considered. The partial slip is controlled by a dimensionless slip factor, which varies between zero （total adhesion） and infinity （full slip）. Suitable similarity transformations are used to reduce the resulting highly nonlinear partial differential equations into ordinary differential equations. The issue of paucity of boundary conditions is addressed and an effective numerical scheme is adopted to solve the obtained differential equations even without augmenting any extra boundary conditions. The important findings in this communication are the combined effects of the partial slip, magnetic interaction parameter and the second grade fluid parameter on the velocity and temperature fields. It is interesting to find that the slip increases the momentum and thermal boundary layer thickness. As the slip increases in magnitude, permitting more fluid to slip past the sheet, the skin friction coefficient decreases in magnitude and approaches zero for higher values of the slip parameter, i.e., the fluid behaves as though it were inviscid. The presence of a magnetic field has also substantial effects on velocity and temperature fields.展开更多
A numerical study of partial slip boundary condition is investigated. The stagnation-point flow problem involving some physio-chemical parameters has been elucidated. The process involves developing a multivariate mat...A numerical study of partial slip boundary condition is investigated. The stagnation-point flow problem involving some physio-chemical parameters has been elucidated. The process involves developing a multivariate mathematical model for the flow and transforming it into a coupled univariate equation. Key parameters of interest in the study are the buoyancy force, the surface stretching, the unsteadiness, the radiation, the dissipation effects, the slip effects, the species reaction and the magnetic field parameters. It is concluded that the impact of physio-chemical factors significantly alters the kinematics of the flow in order to optimally achieve desired product characteristics.展开更多
If a partial contralateral C7 nerve is transferred to a recipient injured nerve, results are not satisfactory. However, if an entire contralateral C7 nerve is used to repair two nerves, both recipient nerves show goo...If a partial contralateral C7 nerve is transferred to a recipient injured nerve, results are not satisfactory. However, if an entire contralateral C7 nerve is used to repair two nerves, both recipient nerves show good recovery. These findings seem contradictory, as the above two methods use the same donor nerve, only the cutting method of the contralateral C7 nerve is different. To verify whether this can actually result in different repair effects, we divided rats with right total brachial plexus injury into three groups. In the entire root group, the entire contralateral C7 root was transected and transferred to the median nerve of the affected limb. In the posterior division group, only the posterior division of the contralateral C7 root was transected and transferred to the median nerve. In the entire root ＋ posterior division group, the entire contralateral C7 root was transected but only the posterior division was transferred to the median nerve. After neurectomy,the median nerve was repaired on the affected side in the three groups. At 8, 12, and 16 weeks postoperatively, electrophysiological examination showed that maximum amplitude, latency, muscle tetanic contraction force, and muscle fiber cross-sectional area of the flexor digitorum superficialis muscle were significantly better in the entire root and entire root ＋ posterior division groups than in the posterior division group. No significant difference was found between the entire root and entire root ＋ posterior division groups. Counts of myelinated axons in the median nerve were greater in the entire root group than in the entire root ＋ posterior division group, which were greater than the posterior division group. We conclude that for the same recipient nerve, harvesting of the entire contralateral C7 root achieved significantly better recovery than partial harvesting, even if only part of the entire root was used for transfer. This result indicates that the entire root should be used as a donor when transferring contralateral C7 nerve.展开更多
Let p be a prime. For any finite p-group G, the deep transfers T H,G ' : H / H ' → G ' / G " from the maximal subgroups H of index (G:H) = p in G to the derived subgroup G ' are introduced as an ...Let p be a prime. For any finite p-group G, the deep transfers T H,G ' : H / H ' → G ' / G " from the maximal subgroups H of index (G:H) = p in G to the derived subgroup G ' are introduced as an innovative tool for identifying G uniquely by means of the family of kernels ùd(G) =(ker(T H,G ')) (G: H) = p. For all finite 3-groups G of coclass cc(G) = 1, the family ùd(G) is determined explicitly. The results are applied to the Galois groups G =Gal(F3 (∞)/ F) of the Hilbert 3-class towers of all real quadratic fields F = Q(√d) with fundamental discriminants d > 1, 3-class group Cl3(F) □ C3 × C3, and total 3-principalization in each of their four unramified cyclic cubic extensions E/F. A systematic statistical evaluation is given for the complete range 1 d 7, and a few exceptional cases are pointed out for 1 d 8.展开更多
正交时频空(orthogonal time frequency space,OTFS)调制在高多普勒环境下可实现可靠通信,适用于卫星通信等高动态场景。然而,其峰值与平均功率比(peak-to-average power ratio,PAPR)易超出功放线性范围,导致非线性失真。部分传输序列(p...正交时频空(orthogonal time frequency space,OTFS)调制在高多普勒环境下可实现可靠通信,适用于卫星通信等高动态场景。然而,其峰值与平均功率比(peak-to-average power ratio,PAPR)易超出功放线性范围,导致非线性失真。部分传输序列(partial transfer sequence,PTS)算法通过对数据符号分块再选取合适的旋转因子可以抑制PAPR。为提高PTS算法抑制PAPR的能力,提出了一种基于改进的灰狼优化(improved grey wolf optimizer,IGWO)算法的PTS算法,即IGWO-PTS算法,以适应离散组合优化问题并获得更优的子块划分方案,从而获得更好的PAPR抑制能力。推导证明了当相位旋转因子集合元素具有旋转对称性时,相位旋转因子组合空间可以收缩为原来的1 K(K为集合中元素个数),极大程度上降低了系统复杂度。仿真实验表明,IGWO-PTS算法相对于传统算法具有更好的PAPR抑制性能,并且在星地高动态场景下可以保持良好的传输可靠性。展开更多
基金supported by the National Natural Science Foundation of China (Grant No.U1909217)the Zhejiang Natural Science Foundation of China (Grant No.LD21E050001)the Wenzhou Major Science and Technology Innovation Project of China (Grant No.ZG2020051)。
文摘Artificial intelligence(AI),which has recently gained popularity,is being extensively employed in modern fault diagnostic research to preserve the reliability and productivity of machines.The effectiveness of AI is influenced by the quality of the labeled training data.However,in engineering scenarios,available data on mechanical equipment are scarce,and collecting massive amounts of well-annotated fault data to train AI models is expensive and difficult.In response to the inadequacy of training samples,a numerical simulation-based partial transfer learning method for machinery fault diagnosis is proposed.First,a suitable simulation model of critical components in a mechanical system is developed using the finite element method(FEM),and numerical simulation is performed to acquire FEM simulation samples containing different fault types.Second,several synthetic simulation samples are generated to form complete source domain training samples using a generative adversarial network.Subsequently,the partial transfer learning network is trained to extract shared fault characteristics between the simulation and measured samples in the case of class imbalance.Finally,the resulting model is used to diagnose unknown samples from real-world mechanical systems in operation.The proposed method is tested on actual fault samples of bearings and gears obtained from a public dataset and experimental test rig available in our laboratory,achieving average classification accuracy of 99.54%and 99.64%,respectively.Comparison investigations reveal that the proposed method has superior classification and generalization ability when detecting faults in real mechanical systems.
文摘Monte Carlo method was applied to simulate the oscillatory behavior during partial oxidation of methane under non-isothermal condition. The simulation was performed to examine the influences of heat transfer constant and particle size on the kinetic oscillation. The oscillatory period and amplitude were observed to increase with the increase of heat transfer constant. The increase of catalyst particle size was found to result in short oscillatory period and more or less regular oscillations combined with the formation of oxide down to L = 100.
文摘The flow and heat transfer of an electrically conducting non-Newtonian second grade fluid due to a radially stretching surface with partial slip is considered. The partial slip is controlled by a dimensionless slip factor, which varies between zero （total adhesion） and infinity （full slip）. Suitable similarity transformations are used to reduce the resulting highly nonlinear partial differential equations into ordinary differential equations. The issue of paucity of boundary conditions is addressed and an effective numerical scheme is adopted to solve the obtained differential equations even without augmenting any extra boundary conditions. The important findings in this communication are the combined effects of the partial slip, magnetic interaction parameter and the second grade fluid parameter on the velocity and temperature fields. It is interesting to find that the slip increases the momentum and thermal boundary layer thickness. As the slip increases in magnitude, permitting more fluid to slip past the sheet, the skin friction coefficient decreases in magnitude and approaches zero for higher values of the slip parameter, i.e., the fluid behaves as though it were inviscid. The presence of a magnetic field has also substantial effects on velocity and temperature fields.
文摘A numerical study of partial slip boundary condition is investigated. The stagnation-point flow problem involving some physio-chemical parameters has been elucidated. The process involves developing a multivariate mathematical model for the flow and transforming it into a coupled univariate equation. Key parameters of interest in the study are the buoyancy force, the surface stretching, the unsteadiness, the radiation, the dissipation effects, the slip effects, the species reaction and the magnetic field parameters. It is concluded that the impact of physio-chemical factors significantly alters the kinematics of the flow in order to optimally achieve desired product characteristics.
基金supported by the National Natural Science Foundation of China,No.H0605/81501871
文摘If a partial contralateral C7 nerve is transferred to a recipient injured nerve, results are not satisfactory. However, if an entire contralateral C7 nerve is used to repair two nerves, both recipient nerves show good recovery. These findings seem contradictory, as the above two methods use the same donor nerve, only the cutting method of the contralateral C7 nerve is different. To verify whether this can actually result in different repair effects, we divided rats with right total brachial plexus injury into three groups. In the entire root group, the entire contralateral C7 root was transected and transferred to the median nerve of the affected limb. In the posterior division group, only the posterior division of the contralateral C7 root was transected and transferred to the median nerve. In the entire root ＋ posterior division group, the entire contralateral C7 root was transected but only the posterior division was transferred to the median nerve. After neurectomy,the median nerve was repaired on the affected side in the three groups. At 8, 12, and 16 weeks postoperatively, electrophysiological examination showed that maximum amplitude, latency, muscle tetanic contraction force, and muscle fiber cross-sectional area of the flexor digitorum superficialis muscle were significantly better in the entire root and entire root ＋ posterior division groups than in the posterior division group. No significant difference was found between the entire root and entire root ＋ posterior division groups. Counts of myelinated axons in the median nerve were greater in the entire root group than in the entire root ＋ posterior division group, which were greater than the posterior division group. We conclude that for the same recipient nerve, harvesting of the entire contralateral C7 root achieved significantly better recovery than partial harvesting, even if only part of the entire root was used for transfer. This result indicates that the entire root should be used as a donor when transferring contralateral C7 nerve.
文摘Let p be a prime. For any finite p-group G, the deep transfers T H,G ' : H / H ' → G ' / G " from the maximal subgroups H of index (G:H) = p in G to the derived subgroup G ' are introduced as an innovative tool for identifying G uniquely by means of the family of kernels ùd(G) =(ker(T H,G ')) (G: H) = p. For all finite 3-groups G of coclass cc(G) = 1, the family ùd(G) is determined explicitly. The results are applied to the Galois groups G =Gal(F3 (∞)/ F) of the Hilbert 3-class towers of all real quadratic fields F = Q(√d) with fundamental discriminants d > 1, 3-class group Cl3(F) □ C3 × C3, and total 3-principalization in each of their four unramified cyclic cubic extensions E/F. A systematic statistical evaluation is given for the complete range 1 d 7, and a few exceptional cases are pointed out for 1 d 8.
文摘正交时频空(orthogonal time frequency space,OTFS)调制在高多普勒环境下可实现可靠通信,适用于卫星通信等高动态场景。然而,其峰值与平均功率比(peak-to-average power ratio,PAPR)易超出功放线性范围,导致非线性失真。部分传输序列(partial transfer sequence,PTS)算法通过对数据符号分块再选取合适的旋转因子可以抑制PAPR。为提高PTS算法抑制PAPR的能力,提出了一种基于改进的灰狼优化(improved grey wolf optimizer,IGWO)算法的PTS算法,即IGWO-PTS算法,以适应离散组合优化问题并获得更优的子块划分方案,从而获得更好的PAPR抑制能力。推导证明了当相位旋转因子集合元素具有旋转对称性时,相位旋转因子组合空间可以收缩为原来的1 K(K为集合中元素个数),极大程度上降低了系统复杂度。仿真实验表明,IGWO-PTS算法相对于传统算法具有更好的PAPR抑制性能,并且在星地高动态场景下可以保持良好的传输可靠性。
