Abstract:The assessment of cementing quality in well casings is crucial for reservoir protection, ensuring safety and environmental protection in oil and gas exploration and development. Acoustic logging technology, a prominent modern well logging technique, is widely utilized for its sensitivity to the acoustic impedance of the medium, the loss of cement annulus, and the state of bonding interfaces. The foundation of acoustic logging technology lies in the theory of the acoustic wave propagation in a borehole. This article provides an examination of the current research status of the acoustic field theory for both single and double casing wells. Additionally, it introduces various traditional acoustic logging techniques employed both domestically and internationally, summarizing the principles and characteristics inherent in these technologies. Furthermore, the article explores the application of artificial intelligence methods in cementing quality evaluation, highlighting the advantages of various machine learning methods in processing logging data to create a broader function space, and helping logging professionals explore knowledge from high-dimensional spaces in a nonlinear way. In conclusion, the article anticipates potential future directions and trends in acoustic logging technology across five dimensions, offering further development recommendations for the evaluation of cementing quality.

Abstract:Ultrasound neuromodulation offers a non-invasive method for precisely regulating deep brain nuclei, providing a novel method for fundamental neuroscience research and brain disorders treatment. Ultrasound neuromodulation has received widespread attention, becoming a cutting-edge of neuromodulation. This article reviews the research progress in ultrasound neuromodulation, with a focus on the principles and the development of three types of ultrasound neuromodulation devices, including bulk acoustic wave transducers, surface acoustic wave devices, and optoacoustic devices. Additionally, the mechanisms research of advancements in ultrasound neuromodulation are analyzed. Furthermore, biomedical applications of ultrasound neuromodulation are discussed. Finally, this article provides an outlook on ultrasound neuromodulation, and explores the future development of sonogenetics.

Abstract:Complex-shaped structures are commonly seen in industry, and they are high-risk regions of internal defect and even failure during manufacturing and service stages. Ultrasonic non-destructive testing is an effective method to evaluate the manufacturing quality and in-service safety of complex-shaped structures. However, complex surface profile brings challenges to ultrasonic testing, such as difficulties in ultrasonic coupling, surface-conformal scan control, ultrasound incidence and reception, and complex wave propagation behavior. This paper summarizes main research progresses in this field from several aspects, including ultrasonic coupling strategies, transducers, surface conformal scan strategies, surface profile reconstruction, imaging algorithms, and the coupling effects between complex-shaped surface profile and ultrasonic properties of materials. Finally, an outlook on future research trends in ultrasonic imaging of complex-shaped structures is provided, including the testing of three-dimensional structures with ultra-complex irregular surfaces, twodimensional array transducers of high flexibility, and the improvement of ultrasonic imaging algorithms that consider both macro / micro structures and the ultrasonic properties of materials.

Abstract:Coherent perfect absorption can only be realized at specific resonant frequencies or in narrow bands, which greatly limits its usefulness in practical applications. In recent years, the introduction of non-Hermitian modulation and acoustic metamaterials has provided new research ideas for complex acoustic wave manipulation, and resulted in many novel wave-matter interactions that are difficult to realize in natural structures. In this paper, we propose a non-Hermitian acoustic subwavelength cavity-tube coupling model to theoretically derive and demonstrate the evolution of coherent perfect absorption. Coalescence of two coherent perfect absorptions with a bandwidth averaging factor of 12. 825 is realized by tuning the non-Hermitian parameters of the system, and the corresponding broadband perfect absorbing characteristics are observed on the output spectra. This work provides a new way to realize broadband coherent perfect absorption based on non-Hermitian acoustic metamaterials, and also lays a theoretical foundation for the development of new functional devices for broadband acoustic absorption, acoustic detection and other engineering applications.

Abstract:Flow velocity is an important basis for realizing online monitoring and precise control of industrial production processes. In order to accurately measure the distribution of the flow field, a reconstruction method based on the combination of radial basis function and equilibrium optimizer (RBF-EO) algorithm is proposed. The radial basis function is used to approximate and establish the model for reconstructing the acoustic velocity field, and the equilibrium optimizer algorithm is used to solve the ill-posed equations in the reconstruction problem. Numerical simulation and noise resistance test of the algorithm were conducted on a typical four-corner tangential velocity field model, and the algorithm was compared with traditional reconstruction methods such as Tikhonov algorithm, SVD decomposition method, and gray wolf optimization algorithm. The simulation results showed that the algorithm can well reconstruct the flow field distribution with higher reconstruction performance and better noise resistance. Finally, the acoustic measurement experiment of the flow field in the measurement area of 1. 05 m×1. 05 m was carried out in the laboratory. The results were compared with the strip display and anemometer, and the average relative error is 9. 77% between RBF-EO algorithm and anemometer measurement results at 8 measurement points, which verifies the reliability of the acoustic flow field measurement method in this paper.

Abstract:The current ultrasonic wind measurement method based on the time difference method is intermittent measurement. Its accuracy is poor in the background of pulse noise. To address this issue, an array ultrasonic continuous wind measurement method based on fractional low-order covariance is proposed in this article. The method adopts an ultrasonic wind measurement array structure consisting of one transmitting ultrasonic transducer and four receiving transducers. Leveraging this array structure, continuous sampling is implemented and fractional low-order covariance operations are applied to suppress the influence of impulse impact noise. Subsequently, the combination with the multiple signal classification algorithm enables high-precision continuous measurement of wind speed and direction. The effectiveness and superiority of the proposed method are evaluated through simulation comparative experiments and actual measurement experiments. Compared with other ultrasonic wind measurement methods, the proposed method shows stronger noise suppression capabilities and higher wind measurement accuracy. In practical experiments, the measurement errors for wind speed and wind direction are 1. 2% and 2°, respectively, which could meet the fundamental technical requirements of ultrasonic anemometers.

Abstract:The transducer that can accurately excite and respond to zero group velocity (ZGV) Lamb waves is crucial for the application of ZGV Lamb waves detection. The traditional transducers used for ZGV Lamb waves detection suffer from issues such as weak signals and low signal-to-noise ratio. In this paper, a polyvinylidene fluoride (PVDF) comb transducer with good flexibility and high sensitivity is designed, and the excitation response performance of the transducer to ZGV Lamb waves is studied. Firstly, the operating characteristics of the comb transducer are analyzed, and the PVDF comb transducer is designed and manufactured according to the ZGV mode of a thin aluminum plate. Subsequently, the ZGV Lamb waves were excited by the PVDF comb transducer under the pulse signals with different center frequencies, and performance comparison experiments were conducted with PVDF square electrode transducers Finally, the relationship between the voltage response characteristics of the PVDF comb transducer and the thickness of the attachment layer was analyzed. Experimental results demonstrate that the PVDF comb transducer designed and manufactured can accurately excite and respond to the ZGV Lamb waves. Moreover, the relative amplitude of the ZGV frequency domain of the response signals decreases significantly with the increase of the thickness of the attachment layer.

Abstract:Structural health monitoring is widely utilized in outdoor environments, especially under harsh conditions, which can introduce noise into the monitoring system. Therefore, designing an effective denoising strategy to enhance the performance of guided wave damage detection in noisy environments is crucial. This paper introduces a local temporal principal component analysis (PCA) reconstruction approach for denoising guided waves prior to implementing unsupervised damage detection, achieved through novel autoencoder-based reconstruction. Experimental results demonstrate that the proposed denoising method significantly enhances damage detection performance when guided waves are contaminated by noise, with SNR values ranging from 10 to -5 dB. Following the implementation of the proposed denoising approach, the AUC score can elevate from 0. 65 to 0. 96 when dealing with guided waves corrputed by noise at a level of -5 dB. Additionally, the paper provides guidance on selecting the appropriate number of components used in the denoising PCA reconstruction, aiding in the optimization of the damage detection in noisy conditions.

Abstract:Corrosion and cracks are common defects in structural plates. The mode conversion of Lamb waves at these non-perforating damages is a primary factor limiting the quality of Lamb wave imaging. Meanwhile, acoustic diffraction adheres to the Rayleigh criterion, leading to resolution limits in ultrasonic imaging. This paper designed a fully convolutional network to segment and reconstruct the received signals, enabling the automatic extraction of target modes and eliminating interference from clutter and mode conversions. Additionally, a sign coherence factor-total focusing method ( SCF-TFM) is proposed, where the symbolic coherence factor is applied during the total focus method imaging process, suppressing the interference from scattered waves in non-target regions. By considering both amplitude and phase information of the signals, it can partially overcome the limitations of the Rayleigh criterion, achieving super-resolution imaging. Experimental results demonstrate that for a single blind-hole defect, the lateral resolution of the imaging result using this method is 62. 41% higher than that of total focus method, and the signal-to-noise ratio ( SNR) is increased by 58. 23% . For multiple asymmetric blind-hole defects, when the spacing between defects exceeds the Rayleigh resolution limit, the signal-to-noise ratio improves by 92. 89% using this method. When the spacing is below the Rayleigh resolution limit, this method can achieve super-resolution imaging. Keywords:Lamb waves; asymmetric blind hole defects; ful

Abstract:Due to its excellent specific strength, multilayer heterogeneous metal bonded structures are widely used as core components in key areas such as pressurized equipment, ships, and nuclear equipment, etc. Their long-term service in complex and harsh environments inevitably produces a variety of defects and damages, which in turn affects the safety of equipment in service. Ultrasonic guided wave inspection is a potential non-destructive testing method. However, the impedance difference between metal and non-metal bonding layers in multi-layer metal bonding structures complicates the propagation characteristics of Lamb waves, making defect detection and localization using time-based guided wave methods challenging. Therefore, this paper proposes a probabilistic imaging method of damage existence applicable to multilayer structures and combines it with the virtual time reversal technique to detect and localize the defects on the inner surfaces of multilayer heterogeneous metal-bonded structures without benchmarks. The results show that in a plate with a geometry of 300 mm, the difference between the coordinates of the localized defects and the center coordinates of the actual defect location is only 2. 74 mm, which realizes the accurate localization of the damage on the inner surface of the multilayered heterogeneous metal bonded structure K .

Abstract:In this paper, in order to solve the problem of damage localization of anisotropic carbon fiber composite plates, an improved dense array total focusing imaging method was proposed. Firstly, considering the anisotropy of the carbon fiber composite plate, the propagation characteristics of the ultrasonic guided waves in the plate were analyzed by experimental methods, and the group velocity values along different propagation directions were obtained. Secondly the parameters of the dense sensor array were analyzed and optimized,and the directional functions of different array parameters, include the spacing of array elements and the number of array elements, were numerically analyzed, and the parameters of the array were optimized to ensure that the main lobe of the array was narrow, the side lobes were low, and there was no grating lobe. Then, an improved structural defect location algorithm for dense sensor array plates considering the anisotropy of carbon fiber composite plates was proposed. The total focusing algorithm was modified by using the ultrasonic guided waves group velocity values along different propagation directions in the carbon fiber composite plate, and the total focusing imaging of the plate structure was carried out by using the virtual focusing principle. Finally, the positioning accuracy of the dense array total focus imaging method was analyzed by arranging the hole damage experiment of carbon fiber composites. The experimental results showed that the positioning accuracy of improved dense array total focusing imaging algorithm method is 1. 00 mm, compared to using a single group velocity value had high accuracy in locating hole damage defects.

Abstract:Steel epoxy sleeves have found extensive applications in the repair of damage in oil and gas pipelines, and the bonding quality of the resin layer is crucial for the reinforcing effect after repair. In this paper, a method for inspecting the bonding defects in steel epoxy sleeves utilizing Circumferential Shear Horizontal (CSH) guided waves generated by Electromagnetic Acoustic Transducers (EMATs) was proposed. Firstly, the propagation characteristics of CSH0 mode guided wave in the steel epoxy sleeve were studied by establishing a finite element model. Secondly, the feasibility of using CSH0 mode guided wave to detect step-type through-cavity defects pre-made in the bonding layer of the steel epoxy sleeve was explored through a combination of finite element simulation and experimental research. Both simulation and experimental results consistently indicate that the amplitude of the direct wave of the CSH0 mode is basically linearly correlated with the cavity width. This suggests that the method can effectively detect through-type cavity defects in the bonding layer and distinguish their sizes. This verifies the feasibility of the proposed method for detecting bonding defects in steel epoxy sleeves.

Abstract:Rail transportation plays a significant role in contemporary societal production activities. A large number of rails in service are built by using fishplate and bolt connections, leading to frequent impact loading on rail joints, which easily induces crack damage around bolt holes. The early detection and quantitative measurement of bolt hole cracks are crucial for ensuring railway transportation safety and preventing serious accidents. Phased array ultrasonic imaging technology, characterized by high precision, strong environmental adaptability, and convenient implementation, have been widely applied in non-destructive testing of rails. However, reconstructed images on cracks through traditional phased array sector scanning methods is influenced by the tilt angle of cracks, relying on operators′ subjective judgment in industrial practice, making it difficult to achieve quantitative and standardized detection. Therefore, in this paper, a quantitative detection method towards rail bolt hole crack based on ultrasonic plane wave imaging is proposed. Compounded plane wave imaging method is utilized to achieve high-precision reconstruction of the region of interest. Reconstructed images from multiple positions are fused to generate final inspection image, ensuring cracks with different tilt angles are covered. Principle components analysis is deployed to quantitatively evaluate the tilt angle of the cracks. After that, directional maximum intensity projection is utilized to measure the length of the cracks. Experiments on a railway test block shows that the proposed method makes a 100% detection rate for cracks in the range of [-45°,45°]. The maximal measurement error of the proposed method on the location of cracks is 1. 47 mm, which is close to a wavelength. The maximal measurement error of the length is 1. 17 mm which is less than a wavelength. The maximal error of tilt angle of cracks is 5. 01°. The required equipment is simple and can be conveniently mounted on mobile rail inspection vehicles to achieve automatic inspection.

Abstract:Curved-surface components are commonly utilized in the aerospace industry due to their unique structural and mechanical properties. However, the irregular shapes of these components pose challenges in accurately calculating ultrasonic propagation delays during array ultrasonic testing, which can impact defect detection precision. This article proposes a novel frequency-domain reverse time migration imaging technique for array ultrasonic testing of curved surface components that eliminates the need for relying on ultrasonic propagation delays. The method involves utilizing the total focusing method to create an image of the curved surface component, followed by threshold segmentation and curve fitting to reconstruct the surface shape and create a two-dimensional acoustic property distribution model. Subsequently, frequency-domain reverse time migration is used to correlate the forward and backward propagation wavefields, resulting in an internal image of the curved surface component. Experimental results on curved samples show that this method successfully enables internal defect imaging of curved-surface components. Compared with the traditional ultrasonic full-focus method, the imaging quality is improved by more than 66% , and the average quantitative error of defects are reduced by more than 37. 04% .

Abstract:Ultrasound guided waves are sensitive to the biomechanical properties of long bones, and have been widely used in the health evaluation of long bones. Due to the high attenuation characteristics of bones, accurate estimation of the dispersion pattern of broadband coherent guided wave signals in long bones, and then accurate inversion of the material characteristic parameters of long bones, is a research hotspot and difficulty in the field of bone ultrasound. In this paper, a guided wave number estimation method based on the subspace of broadband coherent signal is proposed to extract the guided wave dispersion pattern with high accuracy; on this basis, an ant colony algorithm with global optimization is applied to estimate the material parameters of the long bone from the guided wave pattern, and the quantitative evaluation of the condition of the long bone is successfully realized. Simulation and ex vivo experiments (2 simulated samples and 2 ex vivo bovine bones) jointly verified the validity of the method, and the relative errors between the experimental dispersion and the reference dispersion were 3. 52% , 3. 83% , 3. 35% , and 4. 51% , respectively; for the ex vivo bovine bones, the average relative errors between the estimated values of the cortical bone thickness, longitudinal wave velocity, and transverse wave velocity and the reference values were 3. 10% , 0. 11% , and 0. 03% . In conclusion, the method proposed in this paper provides a new reference for quantitative ultrasonic long bone evaluation, and can also be applied to other solid waveguide dispersion extraction and structural health characterization with high accuracy.

Abstract:Early diagnosis and treatment of osteoporosis can significantly reduce the risk of fractures. The imaging examinations of bone tissue′s physical structure and biochemical composition play an important role in the diagnosis of osteoporosis. In order to overcome the limitations of X-ray-based bone health examination techniques, such as ionizing radiation and inability to characterize the biochemical composition of bone tissue, this article designs an ultrasonic-photoacoustic multimodal imaging instrument. This instrument integrates a real-time wavelength-tunable laser, a multi-mode timing controller, an ultrasound data acquisition and controller, and a high-speed data exchange and transmission module. It utilizes time-division multiplexing and asynchronous imaging strategies to process ultrasound and photoacoustic signals in situ. By combining high-resolution imaging algorithms, it obtains ultrasonic-photoacoustic images of bone tissue. In vitro experiments of cancellous bone phantoms and bovine trabecular bone, as well as in vivo experiments of finger joints, demonstrate that the proposed ultrasonic-photoacoustic dual-mode imaging technology has potential application in the diagnosis of osteoporosis, laying a solid foundation for comprehensive clinical research on bone health evaluation.

Abstract:The development of high-resolution and highly sensitive small blood vessels visualization methods has great clinical significance for the early diagnosis and treatment monitoring of related tissue lesions. Different from traditional focused ultrasound, ultrafast ultrasound Doppler (μDoppler) imaging can detect instantaneous changes of small flows due to the framerate of several thousands. Effective tissue clutter filtering and noise suppression methods are crucial to the quality of μDoppler imaging. The commonly used clutter filtering method is the singular value decomposition ( SVD) method. SVD can separate tissue clutter and blood flow signal quickly by utilizing the difference in spatiotemporal coherence of components. However, it cannot effectively suppress noise. Here we propose a novel clutter filtering method based on generalised scalable robust principal component analysis (GSRPCA), using Schatten p norm and l q norm to strengthen the low-rank constraint and sparse constraint of the RPCA model, and enhance the extraction of blood flow signal. Rat cerebral blood flow imaging results demonstrate that GSRPCA can improve the imaging quality of blood vessels in power Doppler imaging, improving SNR by about 20 dB and improving CNR by about 10 dB compared with SVD. The results of brain functional ultrasound imaging shows that GSRPCA can improve the sensitivity of blood volume changes in small vessels. Relevant methods facilitate the study on clutter filtering methods in ultrafast ultrasound imagin Ke g.

Abstract:In order to address the limitations of traditional handheld ultrasound scanning systems, such as narrow field of view, and nonstandardization, this article presents the design and implementation of comprehensive ultrasound imaging system based on a ring array. This system encompasses a 512-element ultrasonic annular array, a high-performance 256 / 1 024-channel acquisition circuit, an efficient PCIe-based data transmission module, and comprehensive software for acquisition control and rapid imaging. The multi-channel acquisition circuit comprising eight 32 / 128 ultrasonic transceiver control modules enables full-matrix data acquisition and high-speed transmission of 512 annular array elements within 12 seconds, achieving a remarkable data transmission efficiency of 1. 2 Gb / s. The system boasts a broadband frequency range of 0. 16~ 15 MHz and adjustable A/ D sampling rates ranging from 12. 5 ~ 100 MHz, which meets the diverse requirements of clinical and experimental applications. The acquisition control software facilitates multi-mode ultrasound data acquisition, enabling the rapid imaging monitoring and secure storage of full-matrix data for subsequent precise image reconstruction. Phantom and in-vivo experiments show that the system can obtain an imaging range exceeding 10 cm×10 cm, resolve 1 mm abnormalities accurately, and provide detailed visualization of interfaces within biological tissues such as fat, muscle, and bone. These results demonstrate the system′s capability of performing circumferential scanning, producing comprehensive and standardized medical ultrasound images with a wide field of view.

Abstract:Ultrasound tomography technology is rapidly emerging as a focus of medical imaging due to its advantages of non-invasiveness, cost-effectiveness, lack of radiation harm, and portability. However, when ultrasound waves propagate in media with high acoustic impedance contrast such as the musculoskeletal system, complex scattering often occurs, leading to waveform distortion and amplitude attenuation of the received signals, thus limiting the resolution and accuracy of reconstruction. Therefore, we exploit a circular to collect full matrix data for musculoskeletal tissues ( including numerical and in vivo examples), enabling collection of ultrasound signals in various modes including reflection, transmission, and multiple scatterings under full-aperture conditions. Subsequently, multiple algorithms are employed to reconstruct the qualitative and quantitative images of the target. Delay-and-sum technique is utilized to achieve structural imaging of strong reflection interfaces, while time-of-flight tomography imaging aids in reconstructing macro sound speed distribution images. Furthermore, full waveform inversion generates higher-resolution images of sound speed distribution by iteratively optimizing on top of time-of-flight tomography imaging results. Through numerical and experimental tests, the method combining time-of-flight tomography and multi-scale frequency-domain full waveform inversion is validated to precisely reconstruct different tissue components, such as skin, fat, muscle, and bones, achieving 0. 4 mm resolution. The research expands the application scope of ultrasound in medical imaging holding significant clinical value for accurate diagnosis of musculoskeletal disorders.

Abstract:The viscosity of micro liquid can be quickly measured based on the construction of the fundamental relationship between the capillary guided wave attenuation rate and the liquid viscosity within the waveguide. It is significant for industrial and medical testing scenarios in which the sample is scarce. However, it is necessary to reduce the pipe size to the capillary level ( the outer diameter is 2 mm or less) to achieve micro-upgrade sample measurement. Traditional guided wave excitation methods face challenges in achieving non-contact transducer assembly and pure guided wave excitation in capillaries. In this paper, a capillary longitudinal guided wave detection sensor suitable for the viscosity detection of trace liquid is developed based on the principle of magnetostriction. Pure L(0,1) modal waveguide are successfully excited on a capillary with an outer diameter of 1. 4 mm and a wall thickness of 0. 1 mm. The sample volume is only 113 μL is required for a single measurement, with good repeatability. The feasibility and practicality of the design are proved on the basis of simulation and experimental exploration of the relevant influencing factors including the distance between the permanent magnet and capillary, capillary wall thickness and excitation frequencies. The results show that the optimal distances between the permanent magnets and capillaries differ at the transmitting and receiving ends, which are 10 mm and 7 mm respectively for the maximum signal amplitude. In the frequency range with low dispersion (below 500 kHz), the detection sensitivity always increases with the frequency. In addition, reducing the wall thickness thinning of capillaries can also improve the viscosity detection sensitivity. Finally, a comparison of the capillary guided wave method with the cone-plate method for measuring standard viscosity liquids showed an error range of no more than 3. 04% , which verifies that the microfine tube guided wave method can achieve high-precision measurement of the viscosity of micro-volume liquid.

Abstract:A signal filtering algorithm ( SVMD-EWT) based on successive variational mode decomposition and empirical wavelet transform is proposed to solve the harmonic separation problem of wideband RF echo signal in ultrasonic tissue harmonic imaging. The signal is decomposed by successive variational modes to acquire the center frequencies of narrow-band modes. The modes are classified according to the local minimum found by Scale-space in empirical wavelet transform. The energy of the modes aliasing in fundamental and harmonic components is chosen as the parameter to optimize the mode boundary of the empirical wavelet transform. Then the empirical wavelet filter is designed to filter the ultrasonic RF echo signals. Simulation and experiments show that the proposed method has better filtering performance than the traditional high-pass filter method with artificially given cutoff frequency and the pulse inversion method dealing with paired echo signals generated by transmitting the inverse phase signal. The contrast of the harmonic breast ultrasound images generated after bandpass filtering and the method proposed in this study are 15. 77 dB and 20. 78 dB, respectively.

Abstract:Gear artefacts are the standard material carriers for gear parameter values, used to transfer the reproduced values from the national gear measurement standard to various gear measuring instruments. This ensures the accuracy and consistency of gear measurements and the quality of gear products. This paper provides a comprehensive overview of the origin and development of gear artefacts, discussing in detail their types, structures, characteristics, measurement techniques and devices, international comparisons, and future development prospects. Over a development history of more than ninety years, gear artefacts have evolved to include diverse types, extended scales, and simplified complexities. As “ tangible” material measures, they remain irreplaceable. However, with the advancement of “intangible” virtual simulation measurement technology, the reliance on “ tangible” material artefacts is expected to decrease, and “intangible” technology may become a new mode of quantity value transmission in the future.

Abstract:The calibration of the stiffness of microcantilever is of great significance in industrial and academic research. The traditional calibration method for microcantilever has drawbacks such as adhesive friction and contact wear. In order to effectively solve the problem of contact friction in traditional stiffness calibration, this paper proposes a non-contact microcantilever stiffness calibration method based on electrostatic force. This method applied static electricity as a standard load to the end of a microcantilever and calculated the stiffness of the microcantilever based on Hooke′s law. Numerical simulations of a parallel plate structure showed that when there is a small deviation in the relative position between the microcantilever and the reference electrode, the electrostatic force deviation is less than 5% . The results of the electrostatic force calibration experiment showed that the stiffness of the microcantilever was 0. 344 N/ m, with a relative measurement uncertainty of 1. 86% . This method is suitable for stiffness calibration of microcantilever and holds significant implications for the research field of micro-force measurements.

Abstract:The images produced by the CMOS sensor of the high-orbit satellite′s optical axis pointing measurement system are prone to degradation due to the harsh space environment. This degradation adversely affects the quality of the images and compromises the accuracy of the spot centroid results. To combat this issue, this study proposes a method for high-precision, real-time determination of spot centroid. Simulation analysis results show that this method can accurately track changes in the spot position within images, validating the feasibility of its step-by-step calculation strategy. The study employed the progressive method, OTSU centroid method, and the Gaussian fitting method for the real-time computation of spot centroids from images acquired by the measurement system. The experimental results show that the progressive method has good real-time performance, the highest success rate of spot location, and the smallest average deviation and standard deviation of centroid calculation, being 0. 026 and 0. 029 pixels, respectively. This approach provides reliable data support for optical axis pointing measurement systems.

Abstract:To address the inefficiencies of ultrasonic bulk wave thickness measurement and insufficient quantitative capability of guided wave detection, a Halbach array electromagnetic ultrasonic transducer integrating shear wave and shear horizontal (SH) guided wave is proposed for metal plate detection. It has the ability to excite both shear-wave and SH0 guided wave without increasing the dimension of the transducer, which combines the functions of high-precision fixed-point thickness measurement and regional defect detection. The transducer prototype was modeled and optimized for magnet array and coil arrangement through finite element simulation, followed by manufacturing and assembly based on the optimized results. Experimental platforms were established for SH wave detection and shear wave thickness measurement function respectively. The experimental results show that the transducer can effectively identify the echoes caused by the iron block adhering to the sample when the size of the block is larger than 35 mm× 10 mm× 20 mm, and the average thickness measurement error is less than 1. 2% . This study combines the deep penetration and high accuracy of ultrasonic bulk wave point thickness measurement with the long-range, non-dispersive scanning capability of SH waves, thereby enhancing the transducer′s detection efficiency and functionality. The transducer shows significant potential for industrial applications.

Abstract:Currently, the low self-harvesting efficiency of three-core cables has become a critical limitation for the application of online monitoring technology along cable routes. To address this issue, this paper proposes a novel magnetic field self-harvesting solution for three-core cables. Unlike traditional energy harvesting approaches based on the principle of transformers, this study innovatively proposes a magnetic field harvesting approach based on motor principles. This approach enhances the coupling between the core and the rotating magnetic field generated by the three-phase current, modifying the normal orientation of coil from tangentially parallel to the cable surface to radially parallel, and identifies the optimal energy harvesting position of device. The simulation results demonstrate that the approach proposed in this study yields higher open-circuit voltage and output power of coil compared to previous reported methods, thereby providing a significant enhancement of magnetic field self-harvesting efficiency. By combining finite element simulations with neural network algorithms, further analysis is conducted to assess the impact of parameters such as primary-current, material and dimensions of magnetic core on the open-circuit voltage of coils. Accordingly the optimization design strategies are proposed. Finally, a prototype is constructed and experiments are conducted in a laboratory setting. It′s found that the maximum output power is 2. 243 mW when the primary-side current is 50 A and three sets of coils possess 2 100 turns.

Abstract:To address the problem of non-consistency and overlapping influence of multi-fault impact resonance bands of rolling bearings, a synchronous diagnosis method for multi-fault bearings based on the cyclic pulse index (CPI) spectrogram is proposed. Firstly, the variation coefficient of the short-time pulse peak moment is taken as the cyclic pulse index to quantitatively characterize the cyclic periodicity and impulsiveness of bearing fault impacts. Then, by combining the frequency band tower decomposition of adaptive redundant lifting wavelet packet with the CPI calculation for the individual frequency band signals, the CPI ratio spectrogram (CPIRgram) is constructed. The optimal resonance band of bearing fault signal is adaptively selected according to the principle of the maximum CPI ratio. Finally, the cyclic pulse spectrum is employed to uniformly characterize each fault feature frequency of the bearing. The simulation and fault test results show that this method does not require prior knowledge of faults or optimization of decomposition parameters. It can accurately detect multiple fault feature frequencies even in the presence of strong noise and random transient interference. The detected fault frequencies show an error of less than 1. 6 Hz compared to their theoretical values. Additionally, the method demonstrates good robustness to variations in fault impact intensity and impact mode, indicating strong potential for practical applications.

Abstract:Accurate estimation of the lithium batteries′ state of health (SoH) and state of charge (SoC) is an important guarantee for the safe operation of new energy vehicles. Aiming at the low accuracy and poor robustness problems of joint SoH-SoC estimation, a joint SoH-SoC estimation method based on BP neural network with variable learning rate and adaptive fading extended H∞ filter is proposed. Firstly, a novel SoH feature parameter based on time interval of unit charging voltage difference is proposed. Secondly, the traditional BP neural network is improved by using a novel BP neural network with variable learning rate to improve the error convergence speed and shorten the weights optimization search time. Finally, by designing a new type of adaptive fading factor to weight the error covariance matrix of traditional extended H infinity filter, an adaptive fading extended H infinity filter algorithm is established to reduce the influence of stale measurement on the estimation results and correspondingly improve the estimation accuracy and robustness of filter. The experimental results show that the SoH and SoC estimation errors of the proposed algorithm are smaller than 0. 35% and 0. 5% , respectively, demonstrating the high estimation accuracy and robustness.

Abstract:Sleep apnea ( SA) affects the quality of sleep and increases the risk of cerebrovascular and cardiovascular diseases. It is advantageous to implement the accurate classification for the timely treatment at the early stage of SA. In this paper, one novel SA classification method utilizing heterogeneous ensemble learning and heterogeneous feature fusion is proposed. Firstly, the SE-ResNet is used as primary classifier of the extracted wavelet time-frequency spectrum from raw electrocardiogram (ECG). Then the 1D CNN-LSTM is used as primary classifier of the extracted R-peak to R-peak interval(RRI) sequence and R-peak amplitude (RAMP) sequence. And the SVM is used as primary classifier of extracted heart rate variability features. Finally, the stacking method is adopted as fusion strategy for heterogeneous ensemble learning, and then another SVM is used as the secondary classifier to implement SA classification. The proposed SA classification method is evaluated on Apnea-ECG dataset, whose accuracy is 89. 12% . Experimental results show that the proposed method utilizes the diversity of primary classifiers and complementarity of heterogeneous features efficiently, which outperforms the conventional SA classification method.

Abstract:Magnetic flux leakage detection is widely used in the defect detection of ferromagnetic materials because of its convenient operation, low requirement of detection environment and high automation. However, the pathology of irregular defect leakage reconstruction leads to low accurate reconstruction results, especially the magnetic leakage reconstruction of 3D irregular defects. Therefore, the 3D defect reconstruction problem is transformed into the 2D defect reconstruction one in this study. A forward model based on coordinate offset magnetic dipole is proposed, which can quickly and accurately calculate the magnetic leakage signal of arbitrary complex defects, and the Newton-Raphson method is used to reconstruct three-dimensional irregular defects. The simulation and experimental results show that compared with the Levenberg-Marquardt reconstruction algorithm, the proposed reconstruction algorithm provides obvious accuracy improvement by reducing the average reconstruction errors of 41% , and average maximum depth errors of 62% , which realizes the rapid reconstruction of 3D irregular defects. Keywords:magnetic leakage detection; defect reconstruction; magnet