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Introducing bond wire diagnosis for multichip IGBT modules is key to the health monitoring of modular multilevel converters (MMCs), which allows for improved field robustness, reliability, and reduced maintenance cost. This paper leverages the crosstalk phenomenon during switching transitions to detect the chip open-circuit faults caused by the bond wire lift-off using typical half-bridge IGBT modules in a multichip-parallel configuration. The cycle-controlled, non-intrusive measurement is conducted under normal operation, when the device under test is at off-state and its complementary switch is during switching transitions. Two specialized health sensitive parameters arising from the dynamic gate loop waveforms are identified and evaluated, including 1) the gate voltage VGE(t3) when the declining collector voltage reaches zero, and 2) the negative peak gate voltage VGE(t4). The sensitivity and stability of these two parameters are compared through theoretical analysis, circuit simulation and practical verification. The results show that VGE(t4) is more suitable for online monitoring, while VGE(t3) is more sensitive than VGE(t4). With managed complexity in gate drives, this proposed health awareness approach is feasible in the submodules of MMC applications, but it can also be used in other power converter topologies incorporating the half-bridge structure.

Background As a promising technology, photoacoustic microscopy (PAM) plays a critical role in diagnosis and assessment of dermatological conditions by providing subtle vascular networks non-invasively. However, the established PAMs are insufficient for clinical dermatology when faced with complex structures of human skin instead of animal models owing to high melanin content and superimposed vasculature for Asians, which cannot balance the spatial resolution and the imaging depth. Objectives To evaluate the ability of bifocal 532/1064-nm alternately illuminated photoacoustic microscopy (BF-PAM) to non-invasively reveal the morphological structure of human skin for improving the diagnosis and therapeutic efficacy of skin diseases. Methods A BF-PAM was developed to capture biopsy-like information of human skin from epidermis to hypodermis. The optical foci of the two excitation beams are staggered in the axial direction to form an extended depth-of-field, which can maintain the lateral resolution and the contrast of PA image. Results The imaging capability of the BF-PAM was demonstrated by depicting the vascular morphology of multilayered skin with imaging depth of ˜3 mm. Furtherly, vascular malformations in port-wine stains skin were quantitatively assessed without the need for any contrast agent, and the distribution, depth and diameter of the ectatic vessels can determine an optimal treatment protocol for port-wine stains lesions. Conclusions The quantitative vascular morphology in the dermis can be used to accurately assess vascular characteristics, in which case it enables clinicians to determine optimum treatment parameters in individual patients. As a non-invasive imaging technique, BF-PAM holds great potential to provide objective assessment to enhance the therapeutic efficacy. Ethical statement The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the Chinese Ethics Committee of Registering Clinical Trials (ChiECRCT20200184) and registered with Chinese Clinical Trial Registry (ChiCTR2000034400). Before skin imaging, written informed consent was taken from all individual participants.

Photoacoustic dermoscopy (PAD) has been proven to visualize the microvascular network within the dermis noninvasively, and has great application potential and advantages. In practice, some subjects are children or unwell and may have difficulty in controlling their breathing or trembling. The artifacts caused by the uncontrollable trembling will degrade the image quality, resulting in deviation of the pathophysiological features. This work introduces a subpixel and on-line motion correction method for clinical application of PAD. The high-accuracy motion correction was realized by the subpixel motion estimation, which was achieved by five-fold upsampling the cross-correlation matrix between A-lines or B-scan images. Since the motion correction algorithm only takes the acquired data as a priori, it can be processed immediately when a B-scan is input, so it can be embedded in the acquisition program, leading to the motion correction during the data acquisition. Moreover, the algorithm was verified by the experimental data of human skin. The results demonstrated that the images after sub-pixel motion correction are obviously improved visually, and the structural similarity index measurement (SSIM) and peak signal-to-noise ratio (PSNR) between adjacent B-scan images after correction are increased by 31.6% and 47.7% compared to the uncorrected images. To conclude, the proposed algorithm can make it robust in terms of accuracy and reliability and will help PAD fulfill its clinical promise.

Currently, most biometric methods mainly use single features, making them easily forged and cracked. In this study, a novel triple-layers biometric recognition method, based on photoacoustic microscopy, is proposed to improve the security of biometric identity recognition. Using the photoacoustic (PA) dermoscope, three-dimensional absorption-structure information of the fingers was obtained. Then, by combining U-Net, Gabor filtering, wavelet analysis and morphological transform, a lightweight algorithm called photoacoustic depth feature recognition algorithm (PADFR) was developed to automatically realize stratification (the fingerprint, blood vessel fingerprint and venous vascular), extracting feature points and identity recognition. The experimental results show that PADFR can automatically recognize the PA hierarchical features with an average accuracy equal to 92.99%. The proposed method is expected to be widely used in biometric identification system due to its high security. This article is protected by copyright. All rights reserved.

Objective: Limited by spherical focused ultrasound transducer (SUT) with a high acoustic numerical aperture, photoacoustic microscopy (PAM) suffers a rapidly degrading sensitivity and lateral resolution as increased depth. In this study, an ellipsoidal focused ultrasound transducer (EUT) was developed to address the above restriction via providing high sensitivity and lateral resolution over a large depth of field (DOF). Methods: To fabricate the EUT, the piezoelectric element was laminated onto a curved steel surface for self-focusing (the ellipsoidal continuous-focus geometry was employed instead of the spherical single-focus one). Additionally, phantoms and in vivo animal experiments were performed by an extend-focus PAM equipped with EUT to characterize its performance. Results: The EUT involved over 30 MHz center frequency and -6 dB bandwidth of 124% with a resolution-invariant focal depth of 1.39 mm, more than 3 times the DOF of the SUT. Conclusion: The in vivo imaging results demonstrated that the EUT was capable of extending the focal depth to get rid of the restriction of the visual field, while the DOF of the SUT was limited by the nature of spherical geometry. Significance: The EUT markedly enhances the image quality at different imaging depths, which has great potential for promoting the biomedical development of in vivo rapid-noninvasive PAM.

A micro-electromechanical system (MEMS) scanning mirror accelerates the raster scanning of optical-resolution photoacoustic microscopy (OR-PAM). However, the nonlinear tilt angular-voltage characteristic of a MEMS mirror introduces distortion into the maximum back-projection image. Moreover, the size of the airy disk, ultrasonic sensor properties, and thermal effects decrease the resolution. Thus, in this study, we proposed a spatial weight matrix (SWM) with a dimensionality reduction for image reconstruction. The three-layer SWM contains the invariable information of the system, which includes a spatial dependent distortion correction and 3D deconvolution. We employed an ordinal-valued Markov random field and the Harris Stephen algorithm, as well as a modified delay-and-sum method during a time reversal. The results from the experiments and a quantitative analysis demonstrate that images can be effectively reconstructed using an SWM; this is also true for severely distorted images. The index of the mutual information between the reference images and registered images was 70.33 times higher than the initial index, on average. Moreover, the peak signal-to-noise ratio was increased by 17.08% after 3D deconvolution. This accomplishment offers a practical approach to image reconstruction and a promising method to achieve a real-time distortion correction for MEMS-based OR-PAM.

Today, photoacoustic imaging (PAI) is widely used to study diseases in the skin, brain, cardiovascular, and other parts. However, these studies are often carried out using physiological slices or model animals, which indicate that many PAI techniques can only be used in the laboratory. In order to promote the transformation of PAI into clinical applications or, more specifically, to extend the application of photoacoustic (PA) microscopy to areas such as the oral cavity, throat, cervix, and abdominal viscera which are difficult to detect with conventional PA microscopy systems, a PAI pen was developed. The PAI pen can be handheld and can perform forward detection and lateral detection. The imaging area is a 2.4 mm diameter circular area. In addition, it can provide a high-speed imaging mode of four frames per second and a high-resolution imaging mode of 0.25 frames per second to meet the different needs of clinical users. In this Letter, the performance of the PAI pen was tested by imaging the phantom and the human oral cavity. The experimental results prove that the PAI pen can clearly image the microvessels of the oral cavity, which indicates that it has the same imaging capability for other similar areas and has a good prospect for assisting the diagnosis of related diseases.

Currently, the reported endoscopic system cannot meet the necessary conditions for real-time and optical-resolution clinical application simultaneously. In this study, by utilizing a high-repetition-rate laser and optimizing the overall structure of the probe, a real-time optical-resolution photoacoustic endoscope was developed, which could image targets in real time while maintaining a relatively constant lateral resolution. The endoscopic system has a best-resolution of 19 μm and a real-time imaging speed of 25 Hz. Experimental results demonstrate that this approach will push the promotion and commercialization of photoacoustic endoscopic imaging in a variety of preclinical and clinical applications.

Micro-electro-mechanical systems (MEMS) scanner has significant advantages of miniature size, fast response and high stability, which is particularly applicable to photoacoustic laparoscopy (PAL). However, tilt angle-voltage curve of electrothermal MEMS shows a nonlinear character, which leads to inevitable nonlinear distortion in photoacoustic imaging. To overcome this problem, a nonlinear distortion correction was developed for the high-resolution forward-scanning electrothermal-MEMS-based PAL. The adaptive resampling method (ARM) was introduced to adaptively calibrate the projection of non-uniform scanning region to match the uniform scanning region. The correction performed low time complexity and high portability owing to the adaptive capacity of distortion decomposition in the reconstruction of physical models. Compared with the sample structure, phantom experiments demonstrated that the distortion was calibrated in all directions and the corrected image provided up to 96.82% high structural similarity in local subset. Furthermore, ARM was applied to imaging the abdominal cavity of rat and the vascular morphology was corrected in real-time display within a delay less than 2 seconds. All these results demonstrated that the nonlinear distortion correction possessed timely and effective correction in PAL, which suggested that it had the potential to employ to any other electrothermal-MEMS-based photoacoustic imaging systems for accurate and quantitative functional imaging.

As the main way of road transportation, highway plays an important role in the development of national economy. The optimum design mathematical model of expressway toll station is established based on the queueing theory. And this paper analyzed the performance of toll plaza, calculated the shape of toll plaza and lane confluence mode. Finally, we use LINGO software to solve the influence of the automatic driving vehicle on the design model

Duncan-Chang model describes the soil stress-strain relationship more accurately when the soil will be loaded. However, it will be inaccurate when the soil is in the unloading process, such as the pit excavation. In order to dispose of properly the Duncan-Chang constitutive model describing accurately the stress-strain relationship of the silty clay under the unloading condition so as to achieve the purpose of engineering application. This paper developed a further modified Duncan-Chang model, which consider intermediate principal stress, lateral unloading process, the parameter λ was introduced to the model; The result by taking the true triaxial test data of a typical silty clay shows that when λ=0.45, a new modified unload Duncan-Chang model for silty clay is effective in solving the problem of descripting unload stress-strain relationship test curves of the silty clay. And for the results further showed it is not suitable for using the sum of the intermediate principal stress σ2 and third principal stress σ3 is equal to 0.5 instead of the intermediate principal stress σ2 through the finite element calculation to the silty clay pit excavation.