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| 1 | Tunable Q-factor wavelet transform denoising with neighboring coefficients and its application to rotating machinery fault diagnosis显示文摘Fault diagnosis of rotating machinery is of great importance to the high quality products and long-term safe operation.However,the useful weak features are usually corrupted by strong background noise,thus increasing the difficulty of the feature extraction.Thereby,a novel denoising method based on the tunable Q-factor wavelet transform(TQWT)using neighboring coefficients is proposed in this article.The emerging TQWT possesses excellent properties compared with the conventional constant-Q wavelet transforms,which can tune Q-factor according to the oscillatory behavior of the signal.Meanwhile,neighboring coefficients denoising is adopted to avoid the overkill of conventional term-by-term thresholding techniques.Because of having the combined advantages of the two methods,the presented denoising method is more practical and effective than other methods.The proposed method is applied to a simulated signal,a rolling element bearing with an outer race defect from antenna transmission chain and a gearbox fault detection case.The processing results demonstrate that the proposed method can successfully identify the fault features,showing that this method is more effective than the conventional wavelet thresholding denoising methods,term-by-term TQWT denoising schemes and spectral kurtosis. | HE WangPeng ZI YanYang CHEN BinQiang WANG Shuai HE ZhengJia | 2013 | Science China(Technological Sciences)2013，56，8： | 27 |
| 2 | Disrupted structural and functional brain connectomes in mild cognitive impairment and Alzheimer's disease显示文摘Alzheimer's disease(AD) is the most common type of dementia, comprising an estimated 60–80% of all dementia cases. It is clinically characterized by impairments of memory and other cognitive functions. Previous studies have demonstrated that these impairments are associated with abnormal structural and functional connections among brain regions, leading to a disconnection concept of AD. With the advent of a combination of non-invasive neuroimaging(structural magnetic resonance imaging(MRI), diffusion MRI, and functional MRI) and neurophysiological techniques(electroencephalography and magnetoencephalography) with graph theoretical analysis, recent studies have shown that patients with AD and mild cognitive impairment(MCI), the prodromal stage of AD, exhibit disrupted topological organization in large-scale brain networks(i.e., connectomics) and that this disruption is signifi cantly correlated with the decline of cognitive functions. In this review, we summarize the recent progress of brain connectomics in AD and MCI, focusing on the changes in the topological organization of large-scale structural and functional brain networks using graph theoretical approaches. Based on the two different perspectives of information segregation and integration, the literature reviewed here suggests that AD and MCI are associated with disrupted segregation and integration in brain networks. Thus, these connectomics studies open up a new window for understanding the pathophysiological mechanisms of AD and demonstrate the potential to uncover imaging biomarkers for clinical diagnosis and treatment evaluation for this disease. | Zhengjia Dai Yong He | 2014 | Neuroscience Bulletin2014，30，2： | 18 |
| 3 | A pseudo wavelet system-based vibration signature extracting method for rotating machinery fault detection显示文摘The rotating machinery,as a typical example of large and complex mechanical systems,is prone to diversified sorts of mechanical faults,especially on their rotating components.Although they can be collected via vibration measurements,the critical fault signatures are always masked by overwhelming interfering contents,therefore difficult to be identified.Moreover,owing to the distinguished time-frequency characteristics of the machinery fault signatures,classical dyadic wavelet transforms(DWTs) are not perfect for detecting them in noisy environments.In order to address the deficiencies of DWTs,a pseudo wavelet system(PWS) is proposed based on the filter constructing strategies of wavelet tight frames.The presented PWS is implemented via a specially devised shift-invariant filterbank structure,which generates non-dyadic wavelet subbands as well as dyadic ones.The PWS offers a finer partition of the vibration signal into the frequency-scale plane.In addition,in order to correctly identify the essential transient signatures produced by the faulty mechanical components,a new signal impulsiveness measure,named spatial spectral ensemble kurtosis(SSEK),is put forward.SSEK is used for selecting the optimal analyzing parameters among the decomposed wavelet subbands so that the masked critical fault signatures can be explicitly recognized.The proposed method has been applied to engineering fault diagnosis cases,in which the processing results showed its effectiveness and superiority to some existing methods. | CHEN BinQiang ZHANG ZhouSuo ZI YanYang YANG ZhiBo HE ZhengJia | 2013 | Science China(Technological Sciences)2013，56，5： | 13 |
| 4 | A data-driven threshold for wavelet sliding window denoising in mechanical fault detection显示文摘Wavelet denoising is an effective approach to extract fault features from strong background noise.It has been widely used in mechanical fault detection and shown excellent performance.However,traditional thresholds are not suitable for nonstationary signal denoising because they set universal thresholds for different wavelet coefficients.Therefore,a data-driven threshold strategy is proposed in this paper.First,the signal is decomposed into different subbands by wavelet transformation.Then a data-driven threshold is derived by estimating the noise power spectral density in different subbands.Since the data-driven threshold is dependent on the noise estimation and adapted to data,it is more robust and accurate for denoising than traditional thresholds.Meanwhile,sliding window method is adopted to set a flexible local threshold.When this method was applied to simulation signal and an inner race fault diagnostic case of dedusting fan bearing,the proposed method has good result and provides valuable advantages over traditional methods in the fault detection of rotating machines. | CHEN YiMin ZI YanYang CAO HongRui HE ZhengJia SUN HaiLiang | 2014 | Science China(Technological Sciences)2014，57，3： | 9 |
| 5 | THE CONSTRUCTION OF WAVELET-BASED TRUNCATED CONICAL SHELL ELEMENT USING B-SPLINE WAVELET ON THE INTERVAL显示文摘在间隔(BSWI ) 上基于 B 花键小浪,截断的圆锥形的壳元素的二个班被构造解决 axisymmetric 问题,即 BSWI 薄截断的圆锥形的壳元素和 BSWI 有独立斜坡变丑插值的中等厚的截断的圆锥形的壳元素。在基于小浪的元素的构造,而不是传统的多项式插值, BSWI 的可伸缩的功能被采用经由变化原则通过构造元素的转变矩阵,然后构造 BSWI 元素形成形状功能。不同于把小浪 Galerkin 方法加在一起的直接小浪的进程,小浪扩大的系数代表的元素的排水量域经由构造转变矩阵被转变成边和内部模式。BSWI 元素为结构的分析联合 B 花键功能近似和各种各样的基于小浪的元素的精确性。圆锥形的壳的一些静态、动态的数字例子被学习比传统的元素与更高的效率和精确表明现在的元素。 | Xiang Jiawei He Zhengjia Chen Xuefeng | 2006 | Acta Mechanica Solida Sinica2006，19，4： | 7 |
| 6 | Construction of adaptive redundant multiwavelet packet and its application to compound faults detection of rotating machinery显示文摘It is significant to detect the fault type and assess the fault level as early as possible for avoiding catastrophic accidents.Due to diversity and complexity,the compound faults detection of rotating machinery under non-stationary operation turns to be a challenging task.Multiwavelet with two or more base functions may match two or more features of compound faults,which may supply a possible solution to compound faults detection.However,the fixed basis functions of multiwavelet transform,which are not related with the vibration signal,may reduce the accuracy of compound faults detection.Moreover,the decomposition results of multiwavelet transform not being own time-invariant is harmful to extract the features of periodical impulses.Furthermore,multiwavelet transform only focuses on the multi-resolution analysis in the low frequency band,and may leave out the useful features of compound faults.To overcome these shortcomings,a novel method called adaptive redundant multiwavelet packet(ARMP) is proposed based on the two-scale similarity transforms.Besides,the relative energy ratio at the characteristic frequency of the concerned component is computed to select the sensitive frequency bands of multiwavelet packet coefficients.The proposed method was used to analyze the compound faults of rolling element bearing.The results showed that the proposed method could enhance the ability of compound faults detection of rotating machinery. | CHEN JingLong ZI YanYang HE ZhengJia WANG XiaoDong | 2012 | Science China(Technological Sciences)2012，55，8： | 7 |
| 7 | Gearbox fault diagnosis of rolling mills using multiwavelet sliding window neighboring coefficient denoising and optimal blind deconvolution显示文摘Fault diagnosis of rolling mills, especially the main drive gearbox, is of great importance to the high quality products and long-term safe operation. However, the useful fault information is usually submerged in heavy background noise under the severe condition. Thereby, a novel method based on multiwavelet sliding window neighboring coefficient denoising and optimal blind deconvolution is proposed for gearbox fault diagnosis in rolling mills. The emerging multiwavelets can seize the important signal processing properties simultaneously. Owing to the multiple scaling and wavelet basis functions, they have the supreme possibility of matching various features. Due to the periodicity of gearbox signals, sliding window is recommended to conduct local threshold denoising, so as to avoid the 'overkill' of conventional universal thresholding techniques. Meanwhile, neighboring coefficient denoising, considering the correlation of the coefficients, is introduced to effectively process the noisy signals in every sliding window. Thus, multiwavelet sliding window neighboring coefficient denoising not only can perform excellent fault extraction, but also accords with the essence of gearbox fault features. On the other hand, optimal blind deconvolution is carried out to highlight the denoised features for operators' easy identification. The filter length is vital for the effective and meaningful results. Hence, the foremost filter length selection based on the kurtosis is discussed in order to full benefits of this technique. The new method is applied to two gearbox fault diagnostic cases of hot strip finishing mills, compared with multiwavelet and scalar wavelet methods with/without optimal blind deconvolution. The results show that it could enhance the ability of fault detection for the main drive gearboxes. | YUAN Jing HE ZhengJia ZI YanYang LIU Han | 2009 | Science China(Technological Sciences)2009，52，10： | 7 |
| 8 | Crack location identification of rotating rotor systems using operating deflection shape data显示文摘Crack location identification, as one key destination of structural health monitoring, is still a challenge for operating rotor systems. The operating deflection shape (ODS), which represents a visual description of the structural vibration patterns under operating conditions, has been gaining importance for structure damage detection in recent years. The ODS carries damage information of a structure, however, it is also difficult to detect weak cracks of rotor directly. The approximate waveform capacity dimension (AWCD) method was successfully applied to damage detection of plates and beam-like structures. In this paper,a strategic approach that combines ODS and weighted AWCD is proposed for crack location identification of the rotating rotor.To eliminate the false peaks of AWCD and obtain desirable results, a weight factor and ODS curvature data are introduced to the expression of the weighted AWCD. The effectiveness of the proposed method is validated by numerical simulation and experimental investigation in a cracked rotor system. The results indicate that the proposed approach not only provides good identifying performance for incipient rotor cracks, but also effectively eliminates the fault peaks introduced by the inflexion locations of ODSs. Moreover, the proposed approach proves promising in detecting crack locations of rotating rotor systems. | ZHANG ChunLin LI Bing YANG ZhiBo XIAO WenRong HE ZhengJia | 2013 | Science China(Technological Sciences)2013，56，7： | 6 |
| 9 | Fault feature enhancement of gearbox in combined machining center by using adaptive cascade stochastic resonance显示文摘The difficulty to select the best system parameters restricts the engineering application of stochastic resonance(SR) . An adaptive cascade stochastic resonance(ACSR) is proposed in the present study. The proposed method introduces correlation theory into SR,and uses correlation coefficient of the input signals and noise as a weight to construct the weighted signal-to-noise ratio(WSNR) index. The influence of high frequency noise is alleviated and the signal-to-noise ratio index used in traditional SR is improved accordingly. The ACSR with WSNR can obtain optimal parameters adaptively. And it is not necessary to predict the exact frequency of the target signal. In addition,through the secondary utilization of noise,ACSR makes the signal output waveform smoother and the fluctuation period more obvious. Simulation example and engineering application of gearbox fault diagnosis demonstrate the effectiveness and feasibility of the proposed method. | LI Bing LI JiMeng HE ZhengJia | 2011 | Science China(Technological Sciences)2011，54，12： | 6 |
| 10 | Effect of Temperature on the Synthesis of SiC Coating on Carbon Fibers by the Reaction of SiO with the Deposited Pyrolytic Carbon Layer显示文摘The influence of reaction temperature on the preparation of SiC coating on carbon fibers by the reaction of silicon monoxide with the deposited pyrolytic carbon (PyC) layer has been discussed.With rising reaction temperature,the thickness of SiC layer increases and the SiC grain is coarsening.The apparent activation energy for the synthesis of SiC layer is about 103.3 kJ/mol.The oxidation resistance of carbon fiber can be improved by the SiC/PyC layers significantly.The initial oxidation temperature of the SiC/PyC coated carbon fiber is about 300℃ higher than that of the uncoated carbon fiber.The oxidation of the SiC/PyC coated carbon fiber is owing to the diffusion of oxygen through the cracks generated by the mismatch of thermal expansion. | Hejun Li,Haibo Ouyang,Lehua Qi,Yulei Zhang,Zhengjia Li and Jianfeng Wei C/C Composites Research Center,Key Laboratory of Ultrahigh Temperature Composites,Northwestern Polytechnical University,Xi an 710072,China | 2010 | Journal of Materials Science & Technology2010，26，3： | 5 |
| 11 | The principle of second generation wavelet for milling cutter breakage detection显示文摘Performance degradation or failure of manufacturing equipment will badly influence machining quality.Because of discontinuousness of the milling process,dynamic signals produced in the milling process become non-stationary.This paper indicates that the essence of SGW(second generation wavelet) transform in non-stationary signal processing is the mathematics principle of inner product transform of a dynamic signal with basis functions.Namely,by means of the inner product operation of a signal with basis functions containing scale function and wavelet function,signal decomposition and reconstruction are obtained.Acoustic emission signals generated in the milling processes of a CNC machine were analyzed by using the basis functions of SGW which are oscillation,decay and compact support.The features of end milling cutter breakage have been extracted,and the influences on machining surface quality have been identified effectively,which provide scientific bases for fault diagnosis,error tracing and quality control. | HE ZhengJia CAO HongRui LI Zhen ZI YanYang CHEN XueFeng | 2009 | Science China(Technological Sciences)2009，52，5： | 5 |
| 12 | Arabidopsis PTD Is Required for Type Ⅰ Crossover Formation and Affects Recombination Frequency in Two Different Chromosomal Regions显示文摘In eukaryotes,crossovers together with sister chromatid cohesion maintain physical association between homologous chromosomes,ensuring accurate chromosome segregation during meiosis I and resulting in exchange of genetic information between homologues.The Arabidopsis PTD(Parting Dancers)gene affects the level of meiotic crossover formation,but its functional relationships with other core meiotic genes,such as AtSPO11-1,AtRAD51,and AtMSH4,are unclear;whether PTD has other functions in meiosis is also unknown.To further analyze PTD function and to test for epistatic relationships,we compared the meiotic chromosome behaviors of Atspol 1-1 ptd and AtradSl ptd double mutants with the relevant single mutants.The results suggest that PTD functions downstream of AtSPOll-1 and AtRAD51 in the meiotic recombination pathway.Furthermore,we found that meiotic defects in rck ptd and Atmsh4 ptd double mutants showed similar meiotic phenotypes to those of the relevant single mutants,providing genetic evidences for roles of PTD and RCK in the type I crossovers pathway.Moreover,we employed a pollen tetrad-based fluorescence method and found that the meiotic crossover frequencies in two genetic intervals were significantly reduced from 6.63%and 22.26%in wild-type to 1.14%and 6.36%,respectively,in the ptd-2 mutant.These results revealed new aspects of PTD function in meiotic crossover formation. | Pingli Lu Asela J.Wijeratne Zhengjia Wang Gregory P.Copenhaver Hong Ma | 2014 | Journal of Genetics and Genomics2014，41，3： | 5 |
| 13 | Stability analysis and controller design for a class of delay systems via observer based on network显示文摘This paper focuses on the problem of stability analysis and controller design for a class of delay systems based on networked control systems. By introducing some free matrix variables, some criteria for stability analysis and observer-based control law design can be obtained by the solving of linear matrix inequalities. A numerical example is also offered to prove the effectiveness of the proposed method. | Xinming CHENG Weihua GUI Zhengjia GAN | 2009 | 控制理论与应用(英文版)2009，7，3： | 3 |
| 14 | Second Generation Wavelet Finite Element and Rotor Cracks Quantitative Identification Method显示文摘The presence of cracks in the rotor is one of the most dangerous and critical defects for rotating machinery.Defect of fatigue cracks may lead to long out-of-service periods,heavy damages of machines and severe economic consequences.With the method of finite element,vibration behavior of cracked rotors and crack detection was received considerable attention in the academic and engineering field.Various researchers studied the response of a cracked rotor and most of them are focused on the crack detection based on vibration behavior of cracked rotors.But it is often difficult to identify the crack parameters quantitatively.Second generation wavelets (SGW) finite element has good ability in modal analysis for singularity problems like a cracked rotor.Based on the fact that the feature of SGW could be designed depending on applications,a multiresolution finite element method is presented.The new model of SGW beam element is constructed.The first three natural frequencies of the rotor with different crack location and size were solved with SGW beam elements,and the database for crack diagnosis is obtained.The first three metrical natural frequencies are employed as inputs of the database and the intersection of the three frequencies contour lines predicted the normalized crack location and size.With the Bently RK4 rotor test rig,rotors with different crack location and size are tested and diagnosed.The experimental results denote the cracks quantitative identification method has higher identification precision.With SGW finite element method,a novel method is presented that has higher precision and faster computing speed to identify the crack location and size. | CHEN Xuefeng LI Bing HE Yuming HE Zhengjia | 2010 | Chinese Journal of Mechanical Engineering2010，23，2： | 3 |
| 15 | A review on empirical mode decomposition in fault diagnosis of rotating machinery显示文摘 | Yaguo Lei Jing Lin Zhengjia He Ming J. Zuo | 2013 | 2013 (1-2)2013，，1： | 3 |
| 16 | I-beam Crack Identification Based on Study of Local Flexibility due to Crack显示文摘Local flexibility of crack plays an important role in crack identification of structures.Analytical methods on local flexibility in a cracked beam with simple geometric crossing sections,such as rectangle,circle,have been made,but there are some difficulties in calculating local flexibility in a cracked beam with complex crossing section,such as pipe and I-beam.In this paper,an analytical method to calculate the local flexibility and rotational spring stiffness due to crack in I-beam is proposed.The local flexibility with respect to various crack depths can be calculated by dividing a cracked I-beam into a series of thin rectangles.The forward and inverse problems in crack detection of I-beam are studied.The forward problem comprises the construction of crack model exclusively for crack section and the construction of a numerically I-beam model to gain crack detection database.The inverse problem consists of the measurement of modal parameters and the detection of crack parameters.Two experiments including measurement of rotational spring stiffness and prediction of cracks in I-beam are conducted.Experimental results based on the current methods indicate that relative error of crack location is less than 3%,while the error of crack depth identification is less than 6%.Crack identification of I-beam is expected to contribute to the development of automated crack detection techniques for railway lines and building skeletons. | LI Bing CHEN Xuefeng HE Zhengjia | 2011 | Chinese Journal of Mechanical Engineering2011，24，6： | 3 |
| 17 | Study of frequency-shifted and re-scaling stochastic resonance and its application to fault diagnosis显示文摘 | Jiyong Tan Xuefeng Chen Junying Wang Huaxin Chen Hongrui Cao Yanyang Zi Zhengjia He | 2008 | Mechanical Systems and Signal Processing2008，，3： | 3 |
| 18 | Mechanical and tribological properties of nanocomposites incorporated with two-dimensional materials显示文摘In recent years, attempts to improve the mechanical properties of composites have increased remarkably owing to the inadequate utilization of matrices in demanding technological systems where efficiency, durability, and environmental compatibility are the key requirements. The search for novel materials that can potentially have enhanced mechanical properties continues. Recent studies have demonstrated that two-dimensional (2D) nanomaterials can act as excellent reinforcements because they possess high modulus of elasticity, high strength, and ultralow friction. By incorporating 2D nanomaterials in a composite, 2D nanomaterial-based composites (2DNBCs) have been developed. In view of this, a critical review of recent mechanical and tribological studies based on 2DNBCs has been undertaken. Matrices such as polymers, ceramics, and metals, as well as most of the representative 2D nanomaterial reinforcements such as graphene, boron nitride (BN), molybdenum disulfide (MoS2), and transition metal carbides and nitrides (MXenes) have been included in this review. Their preparation strategies, intrinsic mechanical properties, friction and lubrication performances, strengthening mechanisms, influencing factors, and potential applications have been comprehensively discussed. A brief summary and prospects are given in the final part, which would be useful in designing and fabricating advanced 2D nanocomposites in the future. | Zhengjia JI Lin ZHANG Guoxin XIE Wenhu XU Dan Guo Jianbin LUO Braham PRAKASH | 2020 | Friction2020，8，5： | 3 |
| 19 | Three-Steps-Meshing Based Multiple Crack Identification for Structures and Its Experimental Studies显示文摘Multiple crack identification plays an important role in vibration-based crack identification of structures. Traditional crack detection method of single crack is difficult to be used in multiple crack diagnosis. A three-step-meshing method for the multiple cracks identification in structures is presented. Firstly, the changes in natural frequency of a structure with various crack locations and depth are accurately obtained by means of wavelet finite element method, and then the damage coefficient method is used to determine the number and the region of cracks. Secondly, different regions in the cracked structure are divided into meshes with different scales, and then the small unit containing cracks in the damaged area is gradually located by iterative computation. Lastly, by finding the points of intersection of three frequency contour lines in the small unit, the crack location and depth are identified. In order to verify the effectiveness of the presented method, a multiple cracks identification experiment is carried out. The diagnostic tests on a cantilever beam under two working conditions show the accuracy of the proposed method: with a maximum error of crack location identification 2.7% and of depth identification 5.2%. The method is able to detect multiple crack of beam with less subdivision and higher precision, and can be developed as a multiple crack detection approach for complicated structures. | LI Bing CHEN Xuefeng HE Zhengjia | 2013 | Chinese Journal of Mechanical Engineering2013，26，2： | 3 |
| 20 | Assessing spatio-temporal variations of precipitation-use efficiency over Tibetan grasslands using MODIS and in-situ observations显示文摘 | Zhengjia LIU Mei HUANG | 2016 | Frontiers of Earth Science2016，10，4： | 3 |
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