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Parametric adaptive time-frequency representation based on time-sheared Gabor atoms 被引量:2
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作者 Ma Shiwei Zhu Xiaojin Chen Guanghua Wang Jian Cao Jialin 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2007年第1期1-7,共7页
A localized parametric time-sheared Gabor atom is derived by convolving a linear frequency modulated factor, modulating in frequency and translating in time to a dilated Gaussian function, which is the generalization ... A localized parametric time-sheared Gabor atom is derived by convolving a linear frequency modulated factor, modulating in frequency and translating in time to a dilated Gaussian function, which is the generalization of Gabor atom and is more delicate for matching most of the signals encountered in practice, especially for those having frequency dispersion characteristics. The time-frequency distribution of this atom concentrates in its time center and frequency center along energy curve, with the curve being oblique to a certain extent along the time axis. A novel parametric adaptive time-frequency distribution based on a set of the derived atoms is then proposed using a adaptive signal subspace decomposition method in frequency domain, which is non-negative time-frequency energy distribution and free of cross-term interference for multicomponent signals. The results of numerical simulation manifest the effectiveness of the approach in time-frequency representation and signal de-noising processing. 展开更多
关键词 time-frequency analysis Gabor atom Time-shear Adaptive signal decomposition time-frequency distribution.
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Underdetermined DOA estimation and blind separation of non-disjoint sources in time-frequency domain based on sparse representation method 被引量:9
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作者 Xiang Wang Zhitao Huang Yiyu Zhou 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2014年第1期17-25,共9页
This paper deals with the blind separation of nonstation-ary sources and direction-of-arrival (DOA) estimation in the under-determined case, when there are more sources than sensors. We assume the sources to be time... This paper deals with the blind separation of nonstation-ary sources and direction-of-arrival (DOA) estimation in the under-determined case, when there are more sources than sensors. We assume the sources to be time-frequency (TF) disjoint to a certain extent. In particular, the number of sources presented at any TF neighborhood is strictly less than that of sensors. We can identify the real number of active sources and achieve separation in any TF neighborhood by the sparse representation method. Compared with the subspace-based algorithm under the same sparseness assumption, which suffers from the extra noise effect since it can-not estimate the true number of active sources, the proposed algorithm can estimate the number of active sources and their cor-responding TF values in any TF neighborhood simultaneously. An-other contribution of this paper is a new estimation procedure for the DOA of sources in the underdetermined case, which combines the TF sparseness of sources and the clustering technique. Sim-ulation results demonstrate the validity and high performance of the proposed algorithm in both blind source separation (BSS) and DOA estimation. 展开更多
关键词 underdetermined blind source separation (UBSS)time-frequency (TF) domain sparse representation methoditerative adaptive approach direction-of-arrival (DOA) estimationclustering validation.
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Parameter estimation of maneuvering targets in OTHR based on sparse time-frequency representation 被引量:2
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作者 Jinfeng Hu Xuan He +3 位作者 Wange Li Hui Ai Huiyong Li Julan Xie 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2016年第3期574-580,共7页
This paper proposes a new method for estimating the parameter of maneuvering targets based on sparse time-frequency transform in over-the-horizon radar(OTHR). In this method, the sparse time-frequency distribution o... This paper proposes a new method for estimating the parameter of maneuvering targets based on sparse time-frequency transform in over-the-horizon radar(OTHR). In this method, the sparse time-frequency distribution of the radar echo is obtained by solving a sparse optimization problem based on the short-time Fourier transform. Then Hough transform is employed to estimate the parameter of the targets. The proposed algorithm has the following advantages: Compared with the Wigner-Hough transform method, the computational complexity of the sparse optimization is low due to the application of fast Fourier transform(FFT). And the computational cost of Hough transform is also greatly reduced because of the sparsity of the time-frequency distribution. Compared with the high order ambiguity function(HAF) method, the proposed method improves in terms of precision and robustness to noise. Simulation results show that compared with the HAF method, the required SNR and relative mean square error are 8 dB lower and 50 dB lower respectively in the proposed method. While processing the field experiment data, the execution time of Hough transform in the proposed method is only 4% of the Wigner-Hough transform method. 展开更多
关键词 over-the-horizon radar(OTHR) maneuvering tar-get parameter estimation sparse time-frequency transform Hough transform
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DOPPLERLET BASED TIME-FREQUENCY REPRESENTATION VIA MATCHING PURSUITS
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作者 Zou Hongxing Zhou Xiaobo Dai Qionghai Li Yanda(State Key Lab. of Intelligent Technology and Systems, Tsinghua University, Beijing 100084) 《Journal of Electronics(China)》 2001年第3期217-227,共11页
A new time-frequency representation called Dopplerlet transform, which uses the dilated, translated and modulated windowed Doppler signals as its basis functions, is proposed, and the Fourier transform, short-time Fou... A new time-frequency representation called Dopplerlet transform, which uses the dilated, translated and modulated windowed Doppler signals as its basis functions, is proposed, and the Fourier transform, short-time Fourier transform (including Gabor transform), wavelet transform, and chirplet transform are formulated in one framework of Dopplerlet transform accordingly.It is proved that the matching pursuits based on Dopplerlet basis functions are convergent, and that the energy of residual signals yielded in the decomposition process decays exponentially. Simulation results show that the matching pursuits with Dopplerlet basis functions can characterize compactly a nonstationary signal. 展开更多
关键词 time-frequency analysis Dopplerlet TRANSFORM PSEUDO time-frequency DISTRIBUTION MATCHING PURSUIT
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Novel Time-frequency Analysis and Representation of EEG
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作者 ZHOU Wei-dong1,YU Ke,JIA Lei1 . Shandong University collego of information, Jinan 250100, China 《Chinese Journal of Biomedical Engineering(English Edition)》 2003年第2期80-85,共6页
A novel method of EEG time-frequency analysis and representation based on a wavelet network is presented. The wavelet network model can represent the EEG data effectively. Based on the wavelet network model, a novel t... A novel method of EEG time-frequency analysis and representation based on a wavelet network is presented. The wavelet network model can represent the EEG data effectively. Based on the wavelet network model, a novel time-frequency energy distribution function is obtained, which has the same time-frequency resolution as Wigner-Ville distribution and is free of cross-term interference. There is a great potential for the use of the novel time-frequency representation of nonstationary biosignal based on a wavelet network in the field of the electrophysiological signal processing and time-frequency analysis. 展开更多
关键词 Electroencephalograpm (EEG) WAVELET networks time-frequency REpresentation Wigner-Ville DISTRIBUTION (WVD)
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真学习还是假参与?——Presentation在高校课堂教学应用中的问题与改进 被引量:1
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作者 鲍传友 吴卓霖 《教学研究》 2024年第2期19-24,共6页
Presentation是目前国内高校教学改革中常用的教学形式之一,在各类学科教学中均有不同程度的应用。这种以增强教学双主体互动为主要特征的教学形式,在实际教学中呈现出学生课堂参与深度不足、学习收获不系统、课堂汇报“一言堂”等问题... Presentation是目前国内高校教学改革中常用的教学形式之一,在各类学科教学中均有不同程度的应用。这种以增强教学双主体互动为主要特征的教学形式,在实际教学中呈现出学生课堂参与深度不足、学习收获不系统、课堂汇报“一言堂”等问题。学生学习是为了完成任务而非获得知识、学生习惯于服从教师权威而非批判性思考、教师教学准备不足与指导环节缺失,以及教学评价的评价主体与形式单一是造成Presenta-tion应用效果不佳的重要因素。提高Presentation的应用效果,需要强化对教学过程的管理,保障Presentation规范实施;改革学业评价方式,促进学生主动思考与合作学习;拓展教学资源供给,为学生自主与合作学习提供更多支持;鼓励教师开展教学行动研究,不断提高教学专业化水平。 展开更多
关键词 课堂汇报 高等教育 合作学习 学生参与
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Working condition recognition of sucker rod pumping system based on 4-segment time-frequency signature matrix and deep learning
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作者 Yun-Peng He Hai-Bo Cheng +4 位作者 Peng Zeng Chuan-Zhi Zang Qing-Wei Dong Guang-Xi Wan Xiao-Ting Dong 《Petroleum Science》 SCIE EI CAS CSCD 2024年第1期641-653,共13页
High-precision and real-time diagnosis of sucker rod pumping system(SRPS)is important for quickly mastering oil well operations.Deep learning-based method for classifying the dynamometer card(DC)of oil wells is an eff... High-precision and real-time diagnosis of sucker rod pumping system(SRPS)is important for quickly mastering oil well operations.Deep learning-based method for classifying the dynamometer card(DC)of oil wells is an efficient diagnosis method.However,the input of the DC as a two-dimensional image into the deep learning framework suffers from low feature utilization and high computational effort.Additionally,different SRPSs in an oil field have various system parameters,and the same SRPS generates different DCs at different moments.Thus,there is heterogeneity in field data,which can dramatically impair the diagnostic accuracy.To solve the above problems,a working condition recognition method based on 4-segment time-frequency signature matrix(4S-TFSM)and deep learning is presented in this paper.First,the 4-segment time-frequency signature(4S-TFS)method that can reduce the computing power requirements is proposed for feature extraction of DC data.Subsequently,the 4S-TFSM is constructed by relative normalization and matrix calculation to synthesize the features of multiple data and solve the problem of data heterogeneity.Finally,a convolutional neural network(CNN),one of the deep learning frameworks,is used to determine the functioning conditions based on the 4S-TFSM.Experiments on field data verify that the proposed diagnostic method based on 4S-TFSM and CNN(4S-TFSM-CNN)can significantly improve the accuracy of working condition recognition with lower computational cost.To the best of our knowledge,this is the first work to discuss the effect of data heterogeneity on the working condition recognition performance of SRPS. 展开更多
关键词 Sucker-rod pumping system Dynamometer card Working condition recognition Deep learning time-frequency signature time-frequency signature matrix
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The W transform and its improved methods for time-frequency analysis of seismic data
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作者 WANG Yanghua RAO Ying ZHAO Zhencong 《Petroleum Exploration and Development》 SCIE 2024年第4期886-896,共11页
The conventional linear time-frequency analysis method cannot achieve high resolution and energy focusing in the time and frequency dimensions at the same time,especially in the low frequency region.In order to improv... The conventional linear time-frequency analysis method cannot achieve high resolution and energy focusing in the time and frequency dimensions at the same time,especially in the low frequency region.In order to improve the resolution of the linear time-frequency analysis method in the low-frequency region,we have proposed a W transform method,in which the instantaneous frequency is introduced as a parameter into the linear transformation,and the analysis time window is constructed which matches the instantaneous frequency of the seismic data.In this paper,the W transform method is compared with the Wigner-Ville distribution(WVD),a typical nonlinear time-frequency analysis method.The WVD method that shows the energy distribution in the time-frequency domain clearly indicates the gravitational center of time and the gravitational center of frequency of a wavelet,while the time-frequency spectrum of the W transform also has a clear gravitational center of energy focusing,because the instantaneous frequency corresponding to any time position is introduced as the transformation parameter.Therefore,the W transform can be benchmarked directly by the WVD method.We summarize the development of the W transform and three improved methods in recent years,and elaborate on the evolution of the standard W transform,the chirp-modulated W transform,the fractional-order W transform,and the linear canonical W transform.Through three application examples of W transform in fluvial sand body identification and reservoir prediction,it is verified that W transform can improve the resolution and energy focusing of time-frequency spectra. 展开更多
关键词 time-frequency analysis W transform Wigner-Ville distribution matching pursuit energy focusing RESOLUTION
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Chlorfenapyr poisoning:mechanisms,clinical presentations,and treatment strategies
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作者 Ji Cheng Yulu Chen +4 位作者 Weidong Wang Xueqi Zhu Zhenluo Jiang Peng Liu Liwen Du 《World Journal of Emergency Medicine》 SCIE CAS CSCD 2024年第3期214-219,共6页
BACKGROUND:Chlorfenapyr is used to kill insects that are resistant to organophosphorus insecticides.Chlorfenapyr poisoning has a high mortality rate and is difficult to treat.This article aims to review the mechanisms... BACKGROUND:Chlorfenapyr is used to kill insects that are resistant to organophosphorus insecticides.Chlorfenapyr poisoning has a high mortality rate and is difficult to treat.This article aims to review the mechanisms,clinical presentations,and treatment strategies for chlorfenapyr poisoning.DATA RESOURCES:We conducted a review of the literature using PubMed,Web of Science,and SpringerLink from their beginnings to the end of October 2023.The inclusion criteria were systematic reviews,clinical guidelines,retrospective studies,and case reports on chlorfenapyr poisoning that focused on its mechanisms,clinical presentations,and treatment strategies.The references in the included studies were also examined to identify additional sources.RESULTS:We included 57 studies in this review.Chlorfenapyr can be degraded into tralopyril,which is more toxic and reduces energy production by inhibiting the conversion of adenosine diphosphate to adenosine triphosphate.High fever and altered mental status are characteristic clinical presentations of chlorfenapyr poisoning.Once it occurs,respiratory failure occurs immediately,ultimately leading to cardiac arrest and death.Chlorfenapyr poisoning is diflcult to treat,and there is no specific antidote.CONCLUSION:Chlorfenapyr is a new pyrrole pesticide.Although it has been identified as a moderately toxic pesticide by the World Health Organization(WHO),the mortality rate of poisoned patients is extremely high.There is no specific antidote for chlorfenapyr poisoning.Therefore,based on the literature review,future efforts to explore rapid and effective detoxification methods,reconstitute intracellular oxidative phosphorylation couplings,identify early biomarkers of chlorfenapyr poisoning,and block the conversion of chlorfenapyr to tralopyril may be helpful for emergency physicians in the diagnosis and treatment of this disease. 展开更多
关键词 Chlorfenapyr poisoning MECHANISM Clinical presentation TREATMENT
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Recent Advances for Global Perspectives on Etiology, Pathophysiology, Clinical Presentations, and Management of Moyamoya Disease
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作者 Maiko Charles Mkwambe Dongchi Zhao Youping Deng 《World Journal of Neuroscience》 CAS 2024年第1期6-23,共18页
Moyamoya disease (MMD) is a condition characterized by the gradual narrowing and blockage of blood vessels in the brain, specifically those in the circle of Willis and the arteries that supply it. This results in redu... Moyamoya disease (MMD) is a condition characterized by the gradual narrowing and blockage of blood vessels in the brain, specifically those in the circle of Willis and the arteries that supply it. This results in reduced blood flow and oxygen to the brain, leading to progressive symptoms and potential complications. The underlying pathophysiological mechanism remains elucidated. However, recent studies have highlighted numerous etiologic factors: abnormal immune complex responses, susceptibility genes, branched-chain amino acids, antibodies, heritable diseases, and acquired diseases, which may be the great potential triggers for the development of moyamoya disease. Its clinical presentation has varying degrees from transient asymptomatic events to significant neurological deficits. Moyamoya disease (MMD) shows different patterns in children and adults. Children with MMD are more susceptible to ischemic events due to decreased blood flow to the brain. Conversely, adults with MMD are more prone to hemorrhagic events involving brain bleeding. Children with MMD may experience a range of symptoms including motor impairments, sensory issues, seizures, headaches, dizziness, cognitive delays, or ongoing neurological problems. Although adults may present with similar clinical symptoms as children, they are more prone to experiencing sudden onset intraventricular, subarachnoid, or intracerebral hemorrhages. One of the challenges in moyamoya disease is the potential for misdiagnosis or delayed diagnosis, particularly when physicians fail to consider MMD as a possible cause in stroke patients. This review aims to provide a comprehensive overview of recent global studies on the pathophysiology of MMD, along with advancements in its management. Additionally, the review will delve into various surgical treatment options for MMD, as well as its rare occurrence alongside atrioventricular malformations. Exciting prospects include the use of autologous bone marrow transplant and the potential role of Connexin 43 protein treatment in the development of moyamoya disease. 展开更多
关键词 Moyamoya Disease (MMD) ETIOLOGY PATHOPHYSIOLOGY Clinical presentations MANAGEMENT Future Promising Avenues
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Clinical Presentation and Treatment Outcomes of Pregnancy-Related Acute Kidney Injury among Pregnant Women Admitted at the Benjamin Mkapa Hospital in Tanzania
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作者 Kessy Shija Hindu Ibrahim +3 位作者 Sylvia Jumbe Bushi Lugoba Stephen Mathew Kibusi Alphonce Chandika 《Open Journal of Nephrology》 2024年第2期157-175,共19页
Background: Globally, PRAKI is among the leading causes of death in pregnant women. The prevalence, causes and outcome of this condition vary among countries due to differences in environmental, socioeconomic, and hea... Background: Globally, PRAKI is among the leading causes of death in pregnant women. The prevalence, causes and outcome of this condition vary among countries due to differences in environmental, socioeconomic, and health delivery systems. The common causes that have been reported in several studies are PIH, Haemorrhages and Sepsis while the outcomes may be either complete renal recovery, progression to CKD and hence dialysis dependency or death. This study aimed at determining clinical presentation and treatment outcomes of Pregnancy-Related Acute Kidney Injury in Pregnant women admitted at the Benjamin Mkapa Hospital, Dodoma, Tanzania. Results: Out of 4007 pregnant women who were admitted to the maternity ward 51 pregnant women were found to have PRAKI. Of those with PRAKI, 74.5% were between 21 to 25 years. The leading causes of PRAKI were PPH 12 (23.53%), Eclampsia 12 (23.53%), and pre-eclampsia 12 (23.5%). Hemodialysis therapy was provided to 22 (43.1%) patients, 15 (29.4%) individuals recovered spontaneously with medical management and 14 (27.5%) missed haemodialysis therapy due to various reasons. The mortality due to PRAKI was 17 (33.3%). Conclusion and Recommendation: Pre-eclampsia/eclampsia and post-partum haemorrhage were found to be the main causes of PRAKI. The mortality related to PRAKI is high and Hemodialysis therapy is vital help to prevent deaths for pregnant women with PRAKI. Pregnant women who develop acute kidney injury should be followed closely and a nephrologist should be consulted early. Early referral should be done by the lower level facilities for all at-risk pregnant women to a specialized multidisciplinary health facility. 展开更多
关键词 Clinical presentation Treatment Outcomes Pregnancy-Related Acute Kidney Injury
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Cultivate Critical Thinking Ability via Students’ Presentations in College English Classes
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作者 HE Zhengye 《Sino-US English Teaching》 2024年第8期383-387,共5页
In the new era when demands for flexible intellectual skills are increasing,strengthening the cultivation of critical thinking ability of students has become one of the key purposes of higher education.This paper inte... In the new era when demands for flexible intellectual skills are increasing,strengthening the cultivation of critical thinking ability of students has become one of the key purposes of higher education.This paper intends to discuss how to cultivate students’critical thinking ability through English classroom presentations.It points out that during the whole process,teachers’guidance plays an indispensable role.Only when both teachers and students are aware that classroom presentations are a golden opportunity for the cultivation of students’critical thinking ability and carry this awareness into their English classes,can English presentations be brought into full play. 展开更多
关键词 critical thinking ability English presentations REFLECTION
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Thinking on Improving Presentation Teaching-Based on the Empirical Analysis of Presentation in College English Classes of Junior Non-English Majors in Universities of Science and Engineering
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作者 DONG Lin 《Sino-US English Teaching》 2024年第9期424-427,共4页
Based on the empirical investigation of presentation in college English classes for junior non-English majors in science and engineering universities,the author explains her own thinking on how to improve presentation... Based on the empirical investigation of presentation in college English classes for junior non-English majors in science and engineering universities,the author explains her own thinking on how to improve presentation teaching from four aspects:setting teaching objectives,selecting teaching contents,using teaching methods,and evaluating and implementing methods. 展开更多
关键词 presentation teaching objective teaching content teaching method evaluation on implementation THINKING
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High-resolution seismic inversion method based on joint data-driven in the time-frequency domain
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作者 Yu Liu Sisi Miao 《Artificial Intelligence in Geosciences》 2024年第1期189-201,共13页
Seismic inversion can be divided into time-domain inversion and frequency-domain inversion based on different transform domains.Time-domain inversion has stronger stability and noise resistance compared to frequencydo... Seismic inversion can be divided into time-domain inversion and frequency-domain inversion based on different transform domains.Time-domain inversion has stronger stability and noise resistance compared to frequencydomain inversion.Frequency domain inversion has stronger ability to identify small-scale bodies and higher inversion resolution.Therefore,the research on the joint inversion method in the time-frequency domain is of great significance for improving the inversion resolution,stability,and noise resistance.The introduction of prior information constraints can effectively reduce ambiguity in the inversion process.However,the existing modeldriven time-frequency joint inversion assumes a specific prior distribution of the reservoir.These methods do not consider the original features of the data and are difficult to describe the relationship between time-domain features and frequency-domain features.Therefore,this paper proposes a high-resolution seismic inversion method based on joint data-driven in the time-frequency domain.The method is based on the impedance and reflectivity samples from logging,using joint dictionary learning to obtain adaptive feature information of the reservoir,and using sparse coefficients to capture the intrinsic relationship between impedance and reflectivity.The optimization result of the inversion is achieved through the regularization term of the joint dictionary sparse representation.We have finally achieved an inversion method that combines constraints on time-domain features and frequency features.By testing the model data and field data,the method has higher resolution in the inversion results and good noise resistance. 展开更多
关键词 time-frequency domain Joint dictionary learning DATA-DRIVEN High-resolution inversion
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The Aesthetic Presentation of Chinese Classical Music in Piano Performance
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作者 Chen Liang 《Journal of Contemporary Educational Research》 2024年第12期127-132,共6页
Piano art has a certain sense of musical beauty,and the performance of piano works can fully reflect the artistic and aesthetic connotations of music works.In piano performance,the aesthetic presentation of Chinese cl... Piano art has a certain sense of musical beauty,and the performance of piano works can fully reflect the artistic and aesthetic connotations of music works.In piano performance,the aesthetic presentation of Chinese classical music can further enhance the performance effect and give the audience and listeners a better artistic experience.Therefore,this paper analyzes the artistic characteristics of Chinese classical music and the characteristics of piano performance and discusses the aesthetic presentation and effect of Chinese classical music in piano performance. 展开更多
关键词 Chinese classical music Piano performance Aesthetic presentation
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Research on Heterogeneous Information Network Link Prediction Based on Representation Learning
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作者 Yan Zhao Weifeng Rao +1 位作者 Zihui Hu Qi Zheng 《Journal of Electronic Research and Application》 2024年第5期32-37,共6页
A heterogeneous information network,which is composed of various types of nodes and edges,has a complex structure and rich information content,and is widely used in social networks,academic networks,e-commerce,and oth... A heterogeneous information network,which is composed of various types of nodes and edges,has a complex structure and rich information content,and is widely used in social networks,academic networks,e-commerce,and other fields.Link prediction,as a key task to reveal the unobserved relationships in the network,is of great significance in heterogeneous information networks.This paper reviews the application of presentation-based learning methods in link prediction of heterogeneous information networks.This paper introduces the basic concepts of heterogeneous information networks,and the theoretical basis of representation learning,and discusses the specific application of the deep learning model in node embedding learning and link prediction in detail.The effectiveness and superiority of these methods on multiple real data sets are demonstrated by experimental verification. 展开更多
关键词 Heterogeneous information network Link prediction presentation learning Deep learning Node embedding
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Application of sparse time-frequency decomposition to seismic data 被引量:3
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作者 王雄文 王华忠 《Applied Geophysics》 SCIE CSCD 2014年第4期447-458,510,共13页
The Gabor and S transforms are frequently used in time-frequency decomposition methods. Constrained by the uncertainty principle, both transforms produce low-resolution time-frequency decomposition results in the time... The Gabor and S transforms are frequently used in time-frequency decomposition methods. Constrained by the uncertainty principle, both transforms produce low-resolution time-frequency decomposition results in the time and frequency domains. To improve the resolution of the time-frequency decomposition results, we use the instantaneous frequency distribution function(IFDF) to express the seismic signal. When the instantaneous frequencies of the nonstationary signal satisfy the requirements of the uncertainty principle, the support of IFDF is just the support of the amplitude ridges in the signal obtained using the short-time Fourier transform. Based on this feature, we propose a new iteration algorithm to achieve the sparse time-frequency decomposition of the signal. The iteration algorithm uses the support of the amplitude ridges of the residual signal obtained with the short-time Fourier transform to update the time-frequency components of the signal. The summation of the updated time-frequency components in each iteration is the result of the sparse timefrequency decomposition. Numerical examples show that the proposed method improves the resolution of the time-frequency decomposition results and the accuracy of the analysis of the nonstationary signal. We also use the proposed method to attenuate the ground roll of field seismic data with good results. 展开更多
关键词 time-frequency analysis sparse time-frequency decomposition nonstationary signal RESOLUTION
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TVAR Time-frequency Analysis for Non-stationary Vibration Signals of Spacecraft 被引量:7
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作者 杨海 程伟 朱虹 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2008年第5期423-432,共10页
Predicting the time-varying auto-spectral density of a spacecraft in high-altitude orbits requires an accurate model for the non-stationary random vibration signals with densely spaced modal frequency. The traditional... Predicting the time-varying auto-spectral density of a spacecraft in high-altitude orbits requires an accurate model for the non-stationary random vibration signals with densely spaced modal frequency. The traditional time-varying algorithm limits prediction accuracy, thus affecting a number of operational decisions. To solve this problem, a time-varying auto regressive (TVAR) model based on the process neural network (PNN) and the empirical mode decomposition (EMD) is proposed. The time-varying system is tracked on-line by establishing a time-varying parameter model, and then the relevant parameter spectrum is obtained. Firstly, the EMD method is utilized to decompose the signal into several intrinsic mode functions (IMFs). Then for each IMF, the PNN is established and the time-varying auto-spectral density is obtained. Finally, the time-frequency distribution of the signals can be reconstructed by linear superposition. The simulation and the analytical results from an example demonstrate that this approach possesses simplicity, effectiveness, and feasibility, as well as higher frequency resolution. 展开更多
关键词 non-stationary random vibration time-frequency distribution process neural network empirical mode decomposition
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Presentation在“电磁场与电磁波”教学中的应用研究 被引量:4
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作者 汤红卫 仲崇山 +1 位作者 孙小燕 王一 《电气电子教学学报》 2016年第1期95-98,共4页
本文探讨了Presentation教学法在专业基础课"电磁场与电磁波"课堂教学中的适用性和特点。教学实践结果表明:课堂中采用Presentation教学法,调动了学生学习的自主性和积极性,实现了良好的教学效果,为学生后续课程的学习奠定了... 本文探讨了Presentation教学法在专业基础课"电磁场与电磁波"课堂教学中的适用性和特点。教学实践结果表明:课堂中采用Presentation教学法,调动了学生学习的自主性和积极性,实现了良好的教学效果,为学生后续课程的学习奠定了良好基础。 展开更多
关键词 电磁场与电磁波 presentation 学习自主性
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提高高校文科课堂教学效能的实证研究——基于Presentation教学法 被引量:11
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作者 黄萍 《华南师范大学学报(社会科学版)》 CSSCI 北大核心 2011年第5期116-121,160,共6页
以Presentation为主的互动教学法的实证探索,对提高课堂教学效能的实践效果,特别是对学生挑战权威意识、批判性阅读和批判性思维学术研究能力和发现、分析、解决问题、团队合作能力的提高进行质与量的分析,说明以Presentation为主的互... 以Presentation为主的互动教学法的实证探索,对提高课堂教学效能的实践效果,特别是对学生挑战权威意识、批判性阅读和批判性思维学术研究能力和发现、分析、解决问题、团队合作能力的提高进行质与量的分析,说明以Presentation为主的互动教学法是提高高校文科课堂效能的有效方法,并对其教学的效能的提高提供可操作的保障性建议。 展开更多
关键词 实证研究 学生能力培养 presentation教学法 课堂教学效能
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