In this study,a comprehensive parametric analysis was performed on non-uniform excitation of V-shaped topography using the boundary element method in time domain.For this purpose,wave scattering analysis was carried o...In this study,a comprehensive parametric analysis was performed on non-uniform excitation of V-shaped topography using the boundary element method in time domain.For this purpose,wave scattering analysis was carried out on a topography subjected to the SV-wave for different predominant frequencies and shape ratios.Based on the numerical results,new coherence and time delay functions are proposed to generate non-uniform ground motion for topographic irregularities.The efficiency and accuracy of the proposed functions for real engineering problems are indicated by comparison with observations reported in previous literature.展开更多
Current research on rail vehicle system vibrations primarily relies on numerical methods,with vibration transfer functions commonly derived through data fitting.However,the physical mechanisms underlying these vibrati...Current research on rail vehicle system vibrations primarily relies on numerical methods,with vibration transfer functions commonly derived through data fitting.However,the physical mechanisms underlying these vibrations are not well understood.To clarify the vibration transfer function and its characteristics,four basic input vectors are defined,and an analytical method is proposed.The vibration transfer functions of the vehicle system are solved,and their spatial coherence is analyzed.The results show that there are two spatial scales and four coherent modes in the vehicle system.The track irregularity wavelengths are combined with two spatial scales to alter the proportions of basic input vectors and then show the characteristics of spatial coherence.Four coherent modes are involved in wheel-rail force and primary suspension force;two coherent modes are involved in bogie vertical motion;and their dominant modes vary with the input frequency.On the other hand,the coherent modes involved in the bogie pitching motion and vehicle body motion are single and fixed over the whole range of frequency.This study presents an analytical method for the rapid solution of dynamic responses in vehicle systems and systematically analyzes the coherence behavior of vibration transfer functions with respect to tracking irregularity wavelengths.展开更多
Indications of dementia disease include deterioration of memory, thinking, behaviour, and the ability to perform everyday activities. Any of these symptoms can lead to stress and difficulties organizing everyday life....Indications of dementia disease include deterioration of memory, thinking, behaviour, and the ability to perform everyday activities. Any of these symptoms can lead to stress and difficulties organizing everyday life. As a way to view factors that support human health and well-being despite stressful situations, Antonovsky introduced a salutogenic model. This model proposes that sense of coherence primarily determines physical and mental health i.e. psychological well-being. Having a sense of coherence in everyday life can reduce the impact of stress on the individual in everyday life. The study’s aim of this study was to explore how participants in existing support groups scored on the Sense of Coherence Scale (SOC), and what they perceived as contributory factors to a meaningful, manageable, and comprehensible everyday life in the presence of dementia using a mixed method. Persons with dementia had the highest scores on the SOC scale and their partners the lowest. Persons with dementia expressed that being with others who understood them made their everyday life comprehensible and manageable. Their partners expressed that learning about dementia was helpful in managing and comprehending everyday situations. The adult children expressed that it was meaningful to care for their parents and they scored slightly higher than the partners on the SOC scale. Long-term ongoing support supplemented with information and social support can contribute to the sense of coherence in persons with dementia and their next of kin.展开更多
This study aimed to investigate the relationship between <span style="font-family:Verdana;">sense</span><span style="font-family:Verdana;"> of coherence and depression and the med...This study aimed to investigate the relationship between <span style="font-family:Verdana;">sense</span><span style="font-family:Verdana;"> of coherence and depression and the mediating role of self-disclosure in lung cancer patients. Α cross-sectional study was conducted in “Sotiria” Chest Diseases Hospital, Greece, with a sample of 200 lung cancer patients. </span><span style="font-family:Verdana;">The</span><span style="font-family:Verdana;"> administered questionnaires included demographic-medical information, SOC-13, Distress Disclosure Index, and CES-D scale. </span><span style="font-family:Verdana;">Analysis</span><span style="font-family:Verdana;"> was performed by SPSS v.23 and PROCESS. Depression was common (41%) and negatively correlated to SOC (rho = -</span><span><span><span style="font-family:;" "=""><span><span style="font-family:Verdana;">0.843, df = 198, p < 0.001), while self-disclosure did not mediate this relationship. Hierarchical linear regression analysis showed that patients with weak SOC, disease recurrence, metastases, low income, and receiving therapy in Day clinic had higher levels of depression. In conclusion, a strong SOC represents a protective factor against depression in lung cancer patients. Consequently, there is a need for targeted interventions, which should mainly increase </span><span style="font-family:Verdana;">SOC</span><span style="font-family:Verdana;"> of these patients.</span></span></span></span></span>展开更多
An algebraic diagonalization method is proposed. As two examples, the Hamiltonians of BCS ground stateunder mean-field approximation and XXZ antiferromagnetic model in linear spin-wave frame have been diagonalized byu...An algebraic diagonalization method is proposed. As two examples, the Hamiltonians of BCS ground stateunder mean-field approximation and XXZ antiferromagnetic model in linear spin-wave frame have been diagonalized byusing SU(2), SU(1,1) Lie algebraic method, respectively. Meanwhile, the eigenstates of the above two models are revealedto be SU(2), SU(1,1) coherent states, respectively. The relation between the usual Bogoliubov Valatin transformationand the algebraic method in a special case is also discussed.展开更多
The aeroengine casing ring forgings have complex cross-section shapes,when the conventional ultrasonic or phased array is applied to detect such curved surfaces,the inspection images always have low resolution and eve...The aeroengine casing ring forgings have complex cross-section shapes,when the conventional ultrasonic or phased array is applied to detect such curved surfaces,the inspection images always have low resolution and even artifacts due to the distortion of the wave beam.In this article,taking a type of aeroengine casing ring forging as an example,the Total Focusing Method(TFM)algorithms for curved surfaces are investigated.First,the Acoustic Field Threshold Segmentation(AFTS)algorithm is proposed to reduce background noise and data calculation.Furthermore,the Vector Coherence Factor(VCF)is adopted to improve the lateral resolution of the TFM imaging.Finally,a series of 0.8 mm diameter Side-Drilled Holes(SDHs)are machined below convex and concave surfaces of the specimen.The quantitative comparison of the detection images using the conventional TFM,AFTS-TFM,VCF-TFM,and AFTS-VCF-TFM is implemented in terms of data volume,imaging Signal-to-Noise Ratio(SNR),and defect echo width.The results show that compared with conventional TFM,the data volume of AFTS-VCF-TFM algorithm for convex and concave is decreased by 32.39%and 73.40%,respectively.Moreover,the average SNR of the AFTS-VCF-TFM is gained up to 40.0 dB,while the average 6 dB-drop echo width of defects is reduced to 0.74 mm.展开更多
In this paper,we point out some practical obstacles arising in realization of compressional optical coherence elastography(OCE)that have not attracted sufficient attention previously.Specif-cally,we discuss(i)complica...In this paper,we point out some practical obstacles arising in realization of compressional optical coherence elastography(OCE)that have not attracted sufficient attention previously.Specif-cally,we discuss(i)complications in quantification of the Young modulus of tissues related to partial adhesion between the OCE probe and soft intervening reference layer sensor,(i)distorting influence of tisue suface curvature/corrugation on the subsurface strain distri-bution mapping,(ii)ways of signal-to-noise mtio(SNR)enhancement in OCE strain mapping when periodic averaging is not realized,and(iv)potentially significant infuence of tissue elastic nonlinearity on quantification of its stifness.Potential pnactical approaches to mitigate the effects of these complications are also described.展开更多
Aims and Objectives: To investigate reliability and validity of the translated Norwegian version of the Family Sense of Coherence scale. Background: The Family Sense of Coherence scale measures the global sense of coh...Aims and Objectives: To investigate reliability and validity of the translated Norwegian version of the Family Sense of Coherence scale. Background: The Family Sense of Coherence scale measures the global sense of coherence in families and might help health professionals to identify vulnerable families and to facilitate the strengthening of coping strategies in families. Design: Cross-sectional. Methods: In total, 264 parents of children with Attention Deficit Hyperactivity Disorder (ADHD) and 157 parents of children in secondary schools in three municipalities responded to a questionnaire regarding the characteristics of the parent and the child, with four scales: Family Sense of Coherence, Sense of Coherence, Family Assessment Device and Well-being. Statistics with Cronbach alpha, intra-class correlation coefficient, independent sample t-test and Pearson’s correlation coefficient were used to establish the reliability and validity of the scale. Results: Internal consistency with Cronbach’s alpha was acceptable and test-retest reliability with intra-class correlation coefficient was sufficient. Known-groups test revealed statistical differences between the two groups of parents as pre-considered and significant correlations between Family Sense of Coherence and Sense of Coherence, Family Assessment Device and Well-being were found. Conclusion: The Norwegian version of Family Sense of Coherence scale can be considered as reliable and valid for the studied population. Relevance to Clinical Practice: The Family Sense of Coherence scale appears to be an appropriate instrument for evaluating and assessing to find vulnerable families who are in need of interventions strengthening the family’s resources.展开更多
In this paper we try to introduce the ladder operators associated with the pseudoharmonic oscillator, after solving the corresponding Schrrdinger equation by using the factorization method. The obtained generalized ra...In this paper we try to introduce the ladder operators associated with the pseudoharmonic oscillator, after solving the corresponding Schrrdinger equation by using the factorization method. The obtained generalized raising and lowering operators naturally lead us to the Dirac representation space of the system which is much easier to work with, in comparison to the functional Hilbert space. The SU（1, 1） dynamical symmetry group associated with the considered system is exactly established through investigating the fact that the deduced operators satisfy appropriate commutation relations. This result enables us to construct two important and distinct classes of Barut-Girardello and Gilmore-Perelomov coherent states associated with the system. Finally, their identities as the most important task are exactly resolved and some of their nonclassical properties are illustrated, numerically.展开更多
An algebraic diagonalization method is proposed. As two examples, the Hamiltonians of BCS ground stateunder mean-field approximation and XXZ antiferromagnetic model in linear spin-wave frame have been diagonalized byu...An algebraic diagonalization method is proposed. As two examples, the Hamiltonians of BCS ground stateunder mean-field approximation and XXZ antiferromagnetic model in linear spin-wave frame have been diagonalized byusing SU(2), SU(1,1) Lie algebraic method, respectively. Meanwhile, the eigenstates of the above two models are revealedto be SU(2), SU(1,1) coherent states, respectively. The relation between the usual Bogoliubov Valatin transformationand the algebraic method in a special case is also discussed.展开更多
The experimental research on zero-net-mass-flux jet closed-loop active control was conducted in the wind tunnel.The mu-level method successfully detected burst events of the coherent structures. The streamwise velocit...The experimental research on zero-net-mass-flux jet closed-loop active control was conducted in the wind tunnel.The mu-level method successfully detected burst events of the coherent structures. The streamwise velocity signals in the turbulent boundary layer were measured by HWA. The drag reduction rate of 16.7% is obtained comparable to that of the open-loop control and saves 75% of the input energy at the asynchronous 100 V/160 Hz control case, which reflects the advantages of the closed-loop control. The experimental findings indicate that the intensity increases in the near-wall region.The perturbation of the PZT vibrators on the skewness factor is concentrated in the region y+< 60. The generation of highspeed fluids is depressed and the downward effect of high-speed fluids weakens. The alteration of energy distribution and the discernible impact of modulation between structures of varying scales are observed. The correlation coefficient exhibits a strong positive correlation, which indicates that the large-scale structures produce modulation effect on small-scale ones.The occurrence of burst events is effectively suppressed. The disturbance has the characteristics of stable periodicity,positive and negative symmetry, low intermittency, and high pulsation strength. The conditional phase waveform shows that the fluctuation amplitude increases, indicating amplitude modulation effects on coherent structures.展开更多
By applying multiple wavelet coherence (MWC) to data from human body movements in triadic interaction, this study quantified triadic synchrony, rhythmic similarity among three interactants. Thirty-nine Japanese underg...By applying multiple wavelet coherence (MWC) to data from human body movements in triadic interaction, this study quantified triadic synchrony, rhythmic similarity among three interactants. Thirty-nine Japanese undergraduates were randomly assigned in a triad, and engaged in a brain-storming task. Triadic synchrony was quantified by calculating MWC to the time-series movement data collected by Kinect v2 sensor. The existence of synchrony was statistically tested by using a pseudo-synchrony paradigm. Results showed that the averaged value of MWC was higher in the experimental participant trio than in those of the pseudo trio in the frequency band of 0.5 - 1 Hz. The result supports the possible utility of applying multiple wavelet coherence to evaluate triadic synchrony in a small group interaction.展开更多
We compare three different methods to extract coherent modes from Doppler backscattering （DBS）, which are center of gravity （COG） of the complex amplitude spectrum, spectrum of DBS phase derivative （phase derivat...We compare three different methods to extract coherent modes from Doppler backscattering （DBS）, which are center of gravity （COG） of the complex amplitude spectrum, spectrum of DBS phase derivative （phase derivative method）, and phase spectrum, respectively. These three methods are all feasible to extract coherent modes, for example, geodesic acoustic mode oscillation. However, there are stilI differences between dealing with high frequency modes （several hundred kHz） and low frequency modes, （several kHz） hiding in DBS signal. There is a significant amount of power at low frequencies in the phase spectrum, which can be removed by using the phase derivative method and COG. High frequency modes are clearer by using the COO and the phase derivative method than the phase spectrum. The spectrum of DBS amplitude does not show the coherent modes detected by using COG, phase derivative method and phase spectrum. When two Doppler shifted peaks exist, coherent modes and their harmonics appear in the spectrum of DBS amplitude, which are introduced by the DBS phase.展开更多
With the rapid development of large-scale regional interconnected power grids,the risk of cascading failures under extreme condi-tions,such as natural disasters and military strikes,has increased significantly.To enha...With the rapid development of large-scale regional interconnected power grids,the risk of cascading failures under extreme condi-tions,such as natural disasters and military strikes,has increased significantly.To enhance the response capability of power systems to extreme events,this study focuses on a method for generator coherency detection.To overcome the shortcomings of the traditional slow coherency method,this paper introduces a novel coherent group identification algorithm based on the theory of nonlinear dynam-ical systems.By analyzing the changing trend of the Euclidean norm of the state variable derivatives in the reduced system,the algorithm can accurately identify the magnitude of the disturbances.Based on the slow coherency methods,the algorithm can correctly recognize coherent generator groups by analyzing system characteristics under varying disturbance magnitudes.This improvement enhances the applicability and accuracy of the coherency detection algorithm under extreme conditions,providing support for emergency control and protection in the power system.Simulations and comparison analyses on IEEE 39-bus system are conducted to validate the accuracy and superiority of the proposed coherent generator group identification method under extreme conditions.展开更多
Single negatively charged nitrogen vacancy(NV-)centers in diamond have emerged as promising platforms for quantum information science,where long coherence times are essential for advancing quantum technologies.However...Single negatively charged nitrogen vacancy(NV-)centers in diamond have emerged as promising platforms for quantum information science,where long coherence times are essential for advancing quantum technologies.However,traditional fabrication methods often introduce lattice damage during the irradiation process used to create vacancies,significantly impairing the spin coherence properties of NV-centers.展开更多
针对复杂电磁环境中因低信噪比、快拍采样数据不足、非高斯杂波干扰及多径传播效应等导致的波达方向(Direction of Arrival,DOA)估计性能退化问题,本文提出了一种基于降维高阶累积量与低秩矩阵重构的多源相干信号的DOA估计算法。首先通...针对复杂电磁环境中因低信噪比、快拍采样数据不足、非高斯杂波干扰及多径传播效应等导致的波达方向(Direction of Arrival,DOA)估计性能退化问题,本文提出了一种基于降维高阶累积量与低秩矩阵重构的多源相干信号的DOA估计算法。首先通过构建四阶累积量矩阵扩展阵列孔径,抑制高斯噪声,提升欠定条件下的信号自由度;随后采用高效的降维策略,显著降低计算复杂度;最后通过交替方向乘子法求解低秩约束下的Toeplitz协方差矩阵重构问题,实现了复杂环境下多源相干信号的高精度定位。实验结果表明,本算法在低信噪比及少快拍数下对多源相干信号依然有出色的估计性能,兼具高精度和强抗干扰特性,有良好的工程实用价值。展开更多
文摘In this study,a comprehensive parametric analysis was performed on non-uniform excitation of V-shaped topography using the boundary element method in time domain.For this purpose,wave scattering analysis was carried out on a topography subjected to the SV-wave for different predominant frequencies and shape ratios.Based on the numerical results,new coherence and time delay functions are proposed to generate non-uniform ground motion for topographic irregularities.The efficiency and accuracy of the proposed functions for real engineering problems are indicated by comparison with observations reported in previous literature.
基金Supported by Fundamental Research Funds for the Central Universities(Grant No.2024QYBS031)Fundamental Research Funds for the Central Universities(Grant No.2022JBQY007)。
文摘Current research on rail vehicle system vibrations primarily relies on numerical methods,with vibration transfer functions commonly derived through data fitting.However,the physical mechanisms underlying these vibrations are not well understood.To clarify the vibration transfer function and its characteristics,four basic input vectors are defined,and an analytical method is proposed.The vibration transfer functions of the vehicle system are solved,and their spatial coherence is analyzed.The results show that there are two spatial scales and four coherent modes in the vehicle system.The track irregularity wavelengths are combined with two spatial scales to alter the proportions of basic input vectors and then show the characteristics of spatial coherence.Four coherent modes are involved in wheel-rail force and primary suspension force;two coherent modes are involved in bogie vertical motion;and their dominant modes vary with the input frequency.On the other hand,the coherent modes involved in the bogie pitching motion and vehicle body motion are single and fixed over the whole range of frequency.This study presents an analytical method for the rapid solution of dynamic responses in vehicle systems and systematically analyzes the coherence behavior of vibration transfer functions with respect to tracking irregularity wavelengths.
文摘Indications of dementia disease include deterioration of memory, thinking, behaviour, and the ability to perform everyday activities. Any of these symptoms can lead to stress and difficulties organizing everyday life. As a way to view factors that support human health and well-being despite stressful situations, Antonovsky introduced a salutogenic model. This model proposes that sense of coherence primarily determines physical and mental health i.e. psychological well-being. Having a sense of coherence in everyday life can reduce the impact of stress on the individual in everyday life. The study’s aim of this study was to explore how participants in existing support groups scored on the Sense of Coherence Scale (SOC), and what they perceived as contributory factors to a meaningful, manageable, and comprehensible everyday life in the presence of dementia using a mixed method. Persons with dementia had the highest scores on the SOC scale and their partners the lowest. Persons with dementia expressed that being with others who understood them made their everyday life comprehensible and manageable. Their partners expressed that learning about dementia was helpful in managing and comprehending everyday situations. The adult children expressed that it was meaningful to care for their parents and they scored slightly higher than the partners on the SOC scale. Long-term ongoing support supplemented with information and social support can contribute to the sense of coherence in persons with dementia and their next of kin.
文摘This study aimed to investigate the relationship between <span style="font-family:Verdana;">sense</span><span style="font-family:Verdana;"> of coherence and depression and the mediating role of self-disclosure in lung cancer patients. Α cross-sectional study was conducted in “Sotiria” Chest Diseases Hospital, Greece, with a sample of 200 lung cancer patients. </span><span style="font-family:Verdana;">The</span><span style="font-family:Verdana;"> administered questionnaires included demographic-medical information, SOC-13, Distress Disclosure Index, and CES-D scale. </span><span style="font-family:Verdana;">Analysis</span><span style="font-family:Verdana;"> was performed by SPSS v.23 and PROCESS. Depression was common (41%) and negatively correlated to SOC (rho = -</span><span><span><span style="font-family:;" "=""><span><span style="font-family:Verdana;">0.843, df = 198, p < 0.001), while self-disclosure did not mediate this relationship. Hierarchical linear regression analysis showed that patients with weak SOC, disease recurrence, metastases, low income, and receiving therapy in Day clinic had higher levels of depression. In conclusion, a strong SOC represents a protective factor against depression in lung cancer patients. Consequently, there is a need for targeted interventions, which should mainly increase </span><span style="font-family:Verdana;">SOC</span><span style="font-family:Verdana;"> of these patients.</span></span></span></span></span>
文摘An algebraic diagonalization method is proposed. As two examples, the Hamiltonians of BCS ground stateunder mean-field approximation and XXZ antiferromagnetic model in linear spin-wave frame have been diagonalized byusing SU(2), SU(1,1) Lie algebraic method, respectively. Meanwhile, the eigenstates of the above two models are revealedto be SU(2), SU(1,1) coherent states, respectively. The relation between the usual Bogoliubov Valatin transformationand the algebraic method in a special case is also discussed.
基金supported by the National Key Research and Development Program of China(No.2019YFB1704500)the National Natural Science Foundation of China(No.51875428)+3 种基金the Key Research and Development Program of Hubei Province,China(No.2020BAB144)the Excellent Youth Foundation of Hubei Province,China(No.2019CFA041)the Innovative Research Team Development Program of Ministry of Education of China(No.IRT_17R83)the 111 Project of China(No.B17034)。
文摘The aeroengine casing ring forgings have complex cross-section shapes,when the conventional ultrasonic or phased array is applied to detect such curved surfaces,the inspection images always have low resolution and even artifacts due to the distortion of the wave beam.In this article,taking a type of aeroengine casing ring forging as an example,the Total Focusing Method(TFM)algorithms for curved surfaces are investigated.First,the Acoustic Field Threshold Segmentation(AFTS)algorithm is proposed to reduce background noise and data calculation.Furthermore,the Vector Coherence Factor(VCF)is adopted to improve the lateral resolution of the TFM imaging.Finally,a series of 0.8 mm diameter Side-Drilled Holes(SDHs)are machined below convex and concave surfaces of the specimen.The quantitative comparison of the detection images using the conventional TFM,AFTS-TFM,VCF-TFM,and AFTS-VCF-TFM is implemented in terms of data volume,imaging Signal-to-Noise Ratio(SNR),and defect echo width.The results show that compared with conventional TFM,the data volume of AFTS-VCF-TFM algorithm for convex and concave is decreased by 32.39%and 73.40%,respectively.Moreover,the average SNR of the AFTS-VCF-TFM is gained up to 40.0 dB,while the average 6 dB-drop echo width of defects is reduced to 0.74 mm.
基金supported by the Russian Federation Government contract No.14.B25.31.0015supported by the Russian Foundation for Basic Research Grant No.16-02-00642Russian President grant for young scientists No.MK-6504.2016.2.
文摘In this paper,we point out some practical obstacles arising in realization of compressional optical coherence elastography(OCE)that have not attracted sufficient attention previously.Specif-cally,we discuss(i)complications in quantification of the Young modulus of tissues related to partial adhesion between the OCE probe and soft intervening reference layer sensor,(i)distorting influence of tisue suface curvature/corrugation on the subsurface strain distri-bution mapping,(ii)ways of signal-to-noise mtio(SNR)enhancement in OCE strain mapping when periodic averaging is not realized,and(iv)potentially significant infuence of tissue elastic nonlinearity on quantification of its stifness.Potential pnactical approaches to mitigate the effects of these complications are also described.
文摘Aims and Objectives: To investigate reliability and validity of the translated Norwegian version of the Family Sense of Coherence scale. Background: The Family Sense of Coherence scale measures the global sense of coherence in families and might help health professionals to identify vulnerable families and to facilitate the strengthening of coping strategies in families. Design: Cross-sectional. Methods: In total, 264 parents of children with Attention Deficit Hyperactivity Disorder (ADHD) and 157 parents of children in secondary schools in three municipalities responded to a questionnaire regarding the characteristics of the parent and the child, with four scales: Family Sense of Coherence, Sense of Coherence, Family Assessment Device and Well-being. Statistics with Cronbach alpha, intra-class correlation coefficient, independent sample t-test and Pearson’s correlation coefficient were used to establish the reliability and validity of the scale. Results: Internal consistency with Cronbach’s alpha was acceptable and test-retest reliability with intra-class correlation coefficient was sufficient. Known-groups test revealed statistical differences between the two groups of parents as pre-considered and significant correlations between Family Sense of Coherence and Sense of Coherence, Family Assessment Device and Well-being were found. Conclusion: The Norwegian version of Family Sense of Coherence scale can be considered as reliable and valid for the studied population. Relevance to Clinical Practice: The Family Sense of Coherence scale appears to be an appropriate instrument for evaluating and assessing to find vulnerable families who are in need of interventions strengthening the family’s resources.
文摘In this paper we try to introduce the ladder operators associated with the pseudoharmonic oscillator, after solving the corresponding Schrrdinger equation by using the factorization method. The obtained generalized raising and lowering operators naturally lead us to the Dirac representation space of the system which is much easier to work with, in comparison to the functional Hilbert space. The SU（1, 1） dynamical symmetry group associated with the considered system is exactly established through investigating the fact that the deduced operators satisfy appropriate commutation relations. This result enables us to construct two important and distinct classes of Barut-Girardello and Gilmore-Perelomov coherent states associated with the system. Finally, their identities as the most important task are exactly resolved and some of their nonclassical properties are illustrated, numerically.
文摘An algebraic diagonalization method is proposed. As two examples, the Hamiltonians of BCS ground stateunder mean-field approximation and XXZ antiferromagnetic model in linear spin-wave frame have been diagonalized byusing SU(2), SU(1,1) Lie algebraic method, respectively. Meanwhile, the eigenstates of the above two models are revealedto be SU(2), SU(1,1) coherent states, respectively. The relation between the usual Bogoliubov Valatin transformationand the algebraic method in a special case is also discussed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12202309,1233000165,12172242,and 12272265)Science and Technology Program of Gansu Province of China(Grant No.22JR5RA304)Tianjin Research Innovation for Postgraduate Students(Grant No.22KJ049)。
文摘The experimental research on zero-net-mass-flux jet closed-loop active control was conducted in the wind tunnel.The mu-level method successfully detected burst events of the coherent structures. The streamwise velocity signals in the turbulent boundary layer were measured by HWA. The drag reduction rate of 16.7% is obtained comparable to that of the open-loop control and saves 75% of the input energy at the asynchronous 100 V/160 Hz control case, which reflects the advantages of the closed-loop control. The experimental findings indicate that the intensity increases in the near-wall region.The perturbation of the PZT vibrators on the skewness factor is concentrated in the region y+< 60. The generation of highspeed fluids is depressed and the downward effect of high-speed fluids weakens. The alteration of energy distribution and the discernible impact of modulation between structures of varying scales are observed. The correlation coefficient exhibits a strong positive correlation, which indicates that the large-scale structures produce modulation effect on small-scale ones.The occurrence of burst events is effectively suppressed. The disturbance has the characteristics of stable periodicity,positive and negative symmetry, low intermittency, and high pulsation strength. The conditional phase waveform shows that the fluctuation amplitude increases, indicating amplitude modulation effects on coherent structures.
文摘By applying multiple wavelet coherence (MWC) to data from human body movements in triadic interaction, this study quantified triadic synchrony, rhythmic similarity among three interactants. Thirty-nine Japanese undergraduates were randomly assigned in a triad, and engaged in a brain-storming task. Triadic synchrony was quantified by calculating MWC to the time-series movement data collected by Kinect v2 sensor. The existence of synchrony was statistically tested by using a pseudo-synchrony paradigm. Results showed that the averaged value of MWC was higher in the experimental participant trio than in those of the pseudo trio in the frequency band of 0.5 - 1 Hz. The result supports the possible utility of applying multiple wavelet coherence to evaluate triadic synchrony in a small group interaction.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10990210 and 11475173the National Magnetic Confinement Fusion Energy Program of China under Grant Nos 2013GB106002 and 2014GB109002
文摘We compare three different methods to extract coherent modes from Doppler backscattering （DBS）, which are center of gravity （COG） of the complex amplitude spectrum, spectrum of DBS phase derivative （phase derivative method）, and phase spectrum, respectively. These three methods are all feasible to extract coherent modes, for example, geodesic acoustic mode oscillation. However, there are stilI differences between dealing with high frequency modes （several hundred kHz） and low frequency modes, （several kHz） hiding in DBS signal. There is a significant amount of power at low frequencies in the phase spectrum, which can be removed by using the phase derivative method and COG. High frequency modes are clearer by using the COO and the phase derivative method than the phase spectrum. The spectrum of DBS amplitude does not show the coherent modes detected by using COG, phase derivative method and phase spectrum. When two Doppler shifted peaks exist, coherent modes and their harmonics appear in the spectrum of DBS amplitude, which are introduced by the DBS phase.
基金supported by National Natural Science Foundation of China(Grant No:52477133)Science and Technology Project of China Southern Power Grid(Grant No.GDKJXM20231178(036100KC23110012)+1 种基金GDKJXM20240389(030000KC24040053))Sanya Yazhou Bay Science and Technology City(Grant No:SKJC-JYRC-2024-66).
文摘With the rapid development of large-scale regional interconnected power grids,the risk of cascading failures under extreme condi-tions,such as natural disasters and military strikes,has increased significantly.To enhance the response capability of power systems to extreme events,this study focuses on a method for generator coherency detection.To overcome the shortcomings of the traditional slow coherency method,this paper introduces a novel coherent group identification algorithm based on the theory of nonlinear dynam-ical systems.By analyzing the changing trend of the Euclidean norm of the state variable derivatives in the reduced system,the algorithm can accurately identify the magnitude of the disturbances.Based on the slow coherency methods,the algorithm can correctly recognize coherent generator groups by analyzing system characteristics under varying disturbance magnitudes.This improvement enhances the applicability and accuracy of the coherency detection algorithm under extreme conditions,providing support for emergency control and protection in the power system.Simulations and comparison analyses on IEEE 39-bus system are conducted to validate the accuracy and superiority of the proposed coherent generator group identification method under extreme conditions.
基金supported by the National Natural Science Foundation of China(Grant Nos.112374012 and 11974208)Shandong Provincial Natural Science Foundation(Grant Nos.ZR2023JQ001 and tsqn202211128)。
文摘Single negatively charged nitrogen vacancy(NV-)centers in diamond have emerged as promising platforms for quantum information science,where long coherence times are essential for advancing quantum technologies.However,traditional fabrication methods often introduce lattice damage during the irradiation process used to create vacancies,significantly impairing the spin coherence properties of NV-centers.
文摘针对复杂电磁环境中因低信噪比、快拍采样数据不足、非高斯杂波干扰及多径传播效应等导致的波达方向(Direction of Arrival,DOA)估计性能退化问题,本文提出了一种基于降维高阶累积量与低秩矩阵重构的多源相干信号的DOA估计算法。首先通过构建四阶累积量矩阵扩展阵列孔径,抑制高斯噪声,提升欠定条件下的信号自由度;随后采用高效的降维策略,显著降低计算复杂度;最后通过交替方向乘子法求解低秩约束下的Toeplitz协方差矩阵重构问题,实现了复杂环境下多源相干信号的高精度定位。实验结果表明,本算法在低信噪比及少快拍数下对多源相干信号依然有出色的估计性能,兼具高精度和强抗干扰特性,有良好的工程实用价值。
