CONSPECTUS:Dislocation loops(DLs),characterized by closed dislocation lines,are a category of defects of vital importance in determining the mechanical properties of metals,particularly under extreme conditions,such a...CONSPECTUS:Dislocation loops(DLs),characterized by closed dislocation lines,are a category of defects of vital importance in determining the mechanical properties of metals,particularly under extreme conditions,such as irradiation,severe plastic deformation,and hydrogen embrittlement.These loops,more intricate than simple dislocations,exhibit far more intricate reaction and evolution pathways arising from the loop type transformation and the associated planar fault transition.This can significantly alter dislocation activities contributing to dislocation channels and complex dislocation networks,which are closely linked to crack initiation and propagation during fracture.Understanding the transformation of DLs is crucial for the development of materials capable of withstanding harsh environments,including those encountered in nuclear reactors,aerospace applications,and hydrogen-rich environments.This Account delves into the computational advancements in studying DL transformations in FCC,HCP,and BCC metals.Traditional simulations often struggle to capture the complexity of DL structures and interactions.To overcome these limitations,a novel computational approach has been developed,enabling precise construction and analysis of DLs.Not only does it automatically account for necessary atom addition or deletion,it is also generic and versatile,applicable for any arbitrary DL morphology with planar fault or fault combination in both pristine metal and complex alloy systems.The new construction approach of DLs provides a critical enabler for studying the transformation of DLs across different crystal structures.In high-symmetry FCC metals,these transformations involve complex unfaulting driven by Shockley and Frank loop interactions,influenced by variations in stress,temperature,and radiation.Meanwhile,HCP metals,with a lower crystal symmetry,exhibit more complex DL transformations due to high anisotropy in the slip systems,variation in Burgers vectors,and different planar faults.Unlike pristine FCC and HCP lattices,ordered intermetallic systems like L12-Ni3Al experience a disruption of translational symmetry within the lattice.The ordered nature of these alloys complicates DL interacting with line dislocation,causing asymmetrical shearing and looping mechanisms.BCC metals,in contrast,exhibit different DL evolution due to the lack of stable stacking faults,leading to stronger interactions with impurities such as carbon and hydrogen.In particular,the interaction between DLs and hydrogen in BCC metals is a critical aspect worth investigating as it can cause severe damage in BCC materials under irradiation,hydrogen embrittlement,and intense deformation.This Account highlights the complex nature of DL transformation in metals under extreme environments and recent computational advances.Differences in the evolution of DLs across crystal structures and their interactions with cracks and solute elements are critical areas for future research.Key challenges include extending DL transformation theories to ordered lattice structures,developing machine-learning-based interatomic potentials,and refining multiscale models to better capture the dynamic behavior of DLs.These efforts will help develop more accurate predictive models,leading to materials with improved resistance to deformation and fracture in harsh environments.展开更多
Loop transformations, such as loop interchange, reversal and skewing, have been unified under linear matrix transformations. A legal transformation matrix is usually generated based upon distance vectors or direction ...Loop transformations, such as loop interchange, reversal and skewing, have been unified under linear matrix transformations. A legal transformation matrix is usually generated based upon distance vectors or direction vectors. Unfortunately, for some nested loops, distance vectors may not be computable and direction vectors, on the other hand, may not contain useful information. We propose the use of linear equations or inequalities of distance vectors to approximate data dependence. This approach is advantageous since (1) many loops having no constant distance vectors have very simple equations of distance vectors; (2) these equations contain more information than direction vectors do, thus the cliance of exploiting potential parallelism is improved.In general, the equations or inequalities that approximate the data dependence of a given nested loop is not unique, hence classification is discussed for the purpose of loop transformation. Efficient algorithms are developed to generate all kinds of linear equations of distance vectors for a given nested loop. The issue of how to obtain a desired transformation matrix from those equations is also addressed.展开更多
The simulation of the transformer transient is one of the indispensable qualifications for improving the performance of transformer protection, the key technique of the transformer's transient simulation is the tr...The simulation of the transformer transient is one of the indispensable qualifications for improving the performance of transformer protection, the key technique of the transformer's transient simulation is the treatment of ferromagnetic elements' loop. Thus the shapes of the primary hysteresis loop and each internal secondary hysteresis loop in the identical magnetism conducting are analyzed, and then it is proposed that there are some fractal characteristics in the relation between them. The fractal phenomenon of the ferromagnetic elements' hysteresis loop in the transformer's transient simulation is first brought forward, the mutuality between the ferromagnetic elements' primary hysteresis loop and its secondary hysteresis loops is revealed in mechanism by using the fractal theory. According to the iterated function system of fractal theory, the secondary hysteresis loops can be generated by the iterative calculation of the primary loop. The simulation results show the validity of this idea.展开更多
A sapphire fibre thermal probe with Cr^3＋ ion-doped end is developed by using the laser heated pedestal growth method. The fluorescence thermal probe offers advantages of compact structure, high performance and abili...A sapphire fibre thermal probe with Cr^3＋ ion-doped end is developed by using the laser heated pedestal growth method. The fluorescence thermal probe offers advantages of compact structure, high performance and ability to withstand high temperature in a detection range from room temperature to 450℃. Based on the fast Fourier transform （FFT）, the fluorescence lifetime is obtained from the tangent function of phase angle of the non-zeroth terms in the FFT result. This method has advantages such as quick calculation, high accuracy and immunity to the background noise. This FFT method is compared with other traditional fitting methods, indicating that the standard deviation of the FFT method is about half of that of the Prony method and about 1/6 of that of the log-fit method. And the FFT method is immune to the background noise involved in a signal. So, the FFT method is an excellent way of processing signals. In addition, a phase-lock amplifier can effectively suppress the noise.展开更多
Insertion loss （IL） is one of the important parameters of asymmetrical digital subscriber loop （ADSL） transformers. In different frequency bands, the factors that affect insertion loss are different. Windings main...Insertion loss （IL） is one of the important parameters of asymmetrical digital subscriber loop （ADSL） transformers. In different frequency bands, the factors that affect insertion loss are different. Windings mainly affect insertion loss in mid and high frequency bands. The effects of winding ways, winding wire diameter and winding turns on insertion loss were discussed. The presented experiment shows that the insertion loss of an ADSL transformer could be under 0.4 dB in mid frequency band when the winding is 30 turns, in which the ADSL transformer satisfies the requirement of total harmonic distortion （THD）. Our experiments also show that the sandwich winding structure is better than the side by side winding structure and the twisted-pair winding structure, and the increase of winding diameter is one means to reduce insertion losses of an ADSL transformer in mid frequency band.展开更多
为解决实际硬件在环(hardware-in-the-loop,HIL)测试平台开发过程中实物电机带来的高复杂度问题及控制策略难以应用的问题,采用TC234和数模转换器(digital to analog converter,DAC)模块设计了一种可代替实物电机的方法,在Simulink中搭...为解决实际硬件在环(hardware-in-the-loop,HIL)测试平台开发过程中实物电机带来的高复杂度问题及控制策略难以应用的问题,采用TC234和数模转换器(digital to analog converter,DAC)模块设计了一种可代替实物电机的方法,在Simulink中搭建了永磁同步电机(permanent magnet synchronous motor,PMSM)的数学模型,并编写为实时数字模型,搭载于TC234完成与其他模块间的通信,完成对实物电机的初步替代。结果表明,在相同输入情况下,实时数字模型与仿真模型输出基本一致,验证了该数字模型的正确性。该方法为降低HIL平台复杂度及后续控制策略的应用提供了必要基础。展开更多
直流电压互感器(direct circuit voltage transformers,DCVTs)的低压输出模拟信号采用电缆传输时既无电气隔离同时易受电磁干扰,因此提出了采用光纤高线性度传输模拟信号的方案。利用双光源-光电探测器分别构成传输通道和闭环负反馈通道...直流电压互感器(direct circuit voltage transformers,DCVTs)的低压输出模拟信号采用电缆传输时既无电气隔离同时易受电磁干扰,因此提出了采用光纤高线性度传输模拟信号的方案。利用双光源-光电探测器分别构成传输通道和闭环负反馈通道,负反馈通道的光电探测器变换电流反馈至输入端对电光-光电传输系数非线性进行抑制,通过控制系统模型分析了非线性抑制控制策略和非线性抑制效果,分析了模拟信号光纤传输系统的电路设计关键要素。对模拟信号光纤传输系统进行开环传输和闭环反馈传输非线性特性对比测试,结果表明,通过闭环负反馈的传输方案将模拟信号光纤传输非线性误差从百分之几提高到了±0.05%以内。最后将模拟信号光纤传输系统应用到DCVT中进行了线性度测试,试验结果表明:模拟信号光纤传输系统能很好地适用于直流配电网中模拟信号电气隔离和消除电磁干扰的应用需求。展开更多
基金the financial support from National Natural Science Foundation of China(NSFC Grants No.12002277 and No.52401010)Natural Sciences and Engineering Research Council of Canada(NSERC)Discovery grant(RGPIN-2023-03628)McGill’s William Dawson Scholar fund.
文摘CONSPECTUS:Dislocation loops(DLs),characterized by closed dislocation lines,are a category of defects of vital importance in determining the mechanical properties of metals,particularly under extreme conditions,such as irradiation,severe plastic deformation,and hydrogen embrittlement.These loops,more intricate than simple dislocations,exhibit far more intricate reaction and evolution pathways arising from the loop type transformation and the associated planar fault transition.This can significantly alter dislocation activities contributing to dislocation channels and complex dislocation networks,which are closely linked to crack initiation and propagation during fracture.Understanding the transformation of DLs is crucial for the development of materials capable of withstanding harsh environments,including those encountered in nuclear reactors,aerospace applications,and hydrogen-rich environments.This Account delves into the computational advancements in studying DL transformations in FCC,HCP,and BCC metals.Traditional simulations often struggle to capture the complexity of DL structures and interactions.To overcome these limitations,a novel computational approach has been developed,enabling precise construction and analysis of DLs.Not only does it automatically account for necessary atom addition or deletion,it is also generic and versatile,applicable for any arbitrary DL morphology with planar fault or fault combination in both pristine metal and complex alloy systems.The new construction approach of DLs provides a critical enabler for studying the transformation of DLs across different crystal structures.In high-symmetry FCC metals,these transformations involve complex unfaulting driven by Shockley and Frank loop interactions,influenced by variations in stress,temperature,and radiation.Meanwhile,HCP metals,with a lower crystal symmetry,exhibit more complex DL transformations due to high anisotropy in the slip systems,variation in Burgers vectors,and different planar faults.Unlike pristine FCC and HCP lattices,ordered intermetallic systems like L12-Ni3Al experience a disruption of translational symmetry within the lattice.The ordered nature of these alloys complicates DL interacting with line dislocation,causing asymmetrical shearing and looping mechanisms.BCC metals,in contrast,exhibit different DL evolution due to the lack of stable stacking faults,leading to stronger interactions with impurities such as carbon and hydrogen.In particular,the interaction between DLs and hydrogen in BCC metals is a critical aspect worth investigating as it can cause severe damage in BCC materials under irradiation,hydrogen embrittlement,and intense deformation.This Account highlights the complex nature of DL transformation in metals under extreme environments and recent computational advances.Differences in the evolution of DLs across crystal structures and their interactions with cracks and solute elements are critical areas for future research.Key challenges include extending DL transformation theories to ordered lattice structures,developing machine-learning-based interatomic potentials,and refining multiscale models to better capture the dynamic behavior of DLs.These efforts will help develop more accurate predictive models,leading to materials with improved resistance to deformation and fracture in harsh environments.
文摘Loop transformations, such as loop interchange, reversal and skewing, have been unified under linear matrix transformations. A legal transformation matrix is usually generated based upon distance vectors or direction vectors. Unfortunately, for some nested loops, distance vectors may not be computable and direction vectors, on the other hand, may not contain useful information. We propose the use of linear equations or inequalities of distance vectors to approximate data dependence. This approach is advantageous since (1) many loops having no constant distance vectors have very simple equations of distance vectors; (2) these equations contain more information than direction vectors do, thus the cliance of exploiting potential parallelism is improved.In general, the equations or inequalities that approximate the data dependence of a given nested loop is not unique, hence classification is discussed for the purpose of loop transformation. Efficient algorithms are developed to generate all kinds of linear equations of distance vectors for a given nested loop. The issue of how to obtain a desired transformation matrix from those equations is also addressed.
文摘The simulation of the transformer transient is one of the indispensable qualifications for improving the performance of transformer protection, the key technique of the transformer's transient simulation is the treatment of ferromagnetic elements' loop. Thus the shapes of the primary hysteresis loop and each internal secondary hysteresis loop in the identical magnetism conducting are analyzed, and then it is proposed that there are some fractal characteristics in the relation between them. The fractal phenomenon of the ferromagnetic elements' hysteresis loop in the transformer's transient simulation is first brought forward, the mutuality between the ferromagnetic elements' primary hysteresis loop and its secondary hysteresis loops is revealed in mechanism by using the fractal theory. According to the iterated function system of fractal theory, the secondary hysteresis loops can be generated by the iterative calculation of the primary loop. The simulation results show the validity of this idea.
文摘A sapphire fibre thermal probe with Cr^3＋ ion-doped end is developed by using the laser heated pedestal growth method. The fluorescence thermal probe offers advantages of compact structure, high performance and ability to withstand high temperature in a detection range from room temperature to 450℃. Based on the fast Fourier transform （FFT）, the fluorescence lifetime is obtained from the tangent function of phase angle of the non-zeroth terms in the FFT result. This method has advantages such as quick calculation, high accuracy and immunity to the background noise. This FFT method is compared with other traditional fitting methods, indicating that the standard deviation of the FFT method is about half of that of the Prony method and about 1/6 of that of the log-fit method. And the FFT method is immune to the background noise involved in a signal. So, the FFT method is an excellent way of processing signals. In addition, a phase-lock amplifier can effectively suppress the noise.
文摘Insertion loss （IL） is one of the important parameters of asymmetrical digital subscriber loop （ADSL） transformers. In different frequency bands, the factors that affect insertion loss are different. Windings mainly affect insertion loss in mid and high frequency bands. The effects of winding ways, winding wire diameter and winding turns on insertion loss were discussed. The presented experiment shows that the insertion loss of an ADSL transformer could be under 0.4 dB in mid frequency band when the winding is 30 turns, in which the ADSL transformer satisfies the requirement of total harmonic distortion （THD）. Our experiments also show that the sandwich winding structure is better than the side by side winding structure and the twisted-pair winding structure, and the increase of winding diameter is one means to reduce insertion losses of an ADSL transformer in mid frequency band.
文摘为解决实际硬件在环(hardware-in-the-loop,HIL)测试平台开发过程中实物电机带来的高复杂度问题及控制策略难以应用的问题,采用TC234和数模转换器(digital to analog converter,DAC)模块设计了一种可代替实物电机的方法,在Simulink中搭建了永磁同步电机(permanent magnet synchronous motor,PMSM)的数学模型,并编写为实时数字模型,搭载于TC234完成与其他模块间的通信,完成对实物电机的初步替代。结果表明,在相同输入情况下,实时数字模型与仿真模型输出基本一致,验证了该数字模型的正确性。该方法为降低HIL平台复杂度及后续控制策略的应用提供了必要基础。
文摘直流电压互感器(direct circuit voltage transformers,DCVTs)的低压输出模拟信号采用电缆传输时既无电气隔离同时易受电磁干扰,因此提出了采用光纤高线性度传输模拟信号的方案。利用双光源-光电探测器分别构成传输通道和闭环负反馈通道,负反馈通道的光电探测器变换电流反馈至输入端对电光-光电传输系数非线性进行抑制,通过控制系统模型分析了非线性抑制控制策略和非线性抑制效果,分析了模拟信号光纤传输系统的电路设计关键要素。对模拟信号光纤传输系统进行开环传输和闭环反馈传输非线性特性对比测试,结果表明,通过闭环负反馈的传输方案将模拟信号光纤传输非线性误差从百分之几提高到了±0.05%以内。最后将模拟信号光纤传输系统应用到DCVT中进行了线性度测试,试验结果表明:模拟信号光纤传输系统能很好地适用于直流配电网中模拟信号电气隔离和消除电磁干扰的应用需求。
