Current mode analog and digital circuit design

In this dissertation, two important current mode circuit design subjects have been explored. In the first part, the switched-current circuit technique has been investigated. The fundamental performance and limitations of this technique are explored. One of the major limitations, the signal distortion caused by clock feedthrough has been substantially reduced by a newly developed clock feedthrough cancellation technique. In addition, a filter synthesis technique has been developed by directly simulating the structure of digital filter. Several experimental CMOS prototypes have been designed and fabricated. The measured frequency and phase responses demonstrated the feasibility of this synthesis technique. In the second part, a new logic family called current-steering logic has been developed. The fundamental performance and characteristics of this technique have been discussed including the basic inverter and NOR gate with DC analysis, transient analysis and power-delay product. It has been shown that the current-steering logic has, a much smaller current spike than conventional CMOS logic circuits, which is especially desirable in mixed-mode applications. Several experimental prototypes have verified the functionality and performance of this new technique

Few-Shot Learning Approaches for Fault Diagnosis Using Vibration Data: A Comprehensive Review

Fault detection and diagnosis play a crucial role in ensuring the reliability and safety of modern industrial systems. For safety and cost considerations, critical equipment and systems in industrial operations are typically not allowed to operate in severe fault states. Moreover, obtaining labeled samples for fault diagnosis often requires significant human effort. This results in limited labeled data for many application scenarios. Thus, the focus of attention has shifted towards learning from a small amount of data. Few-shot learning has emerged as a solution to this challenge, aiming to develop models that can effectively solve problems with only a few samples. This approach has gained significant traction in various fields, such as computer vision, natural language processing, audio and speech, reinforcement learning, robotics, and data analysis. Surprisingly, despite its wide applicability, there have been limited investigations or reviews on applying few-shot learning to the field of mechanical fault diagnosis. In this paper, we provide a comprehensive review of the relevant work on few-shot learning in mechanical fault diagnosis from 2018 to September 2023. By examining the existing research, we aimed to shed light on the potential of few-shot learning in this domain and offer valuable insights for future research directions

A Novel Deep Model with Meta-learning for Rolling Bearing Few-shot Fault Diagnosis

Machine learning, especially deep learning, has been highly successful in data- intensive applications, however, the performance of these models will drop significantly when the amount of the training data amount does not meet the requirement. This leads to the so-called Few-Shot Learning (FSL) problem, which requires the model rapidly generalize to new tasks that containing only a few labeled samples. In this paper, we proposed a new deep model, called deep convolutional meta-learning networks (DCMLN), to address the low performance of generalization under limited data for bearing fault diagnosis. The essential of our approach is to learn a base model from the multiple learning tasks using a support dataset and finetune the learnt parameters using few-shot tasks before it can adapt to the new learning task based on limited training data. The proposed method was compared to several few-shot learning methods, including methods with and without pre-training the embedding mapping, and methods with finetuning the classifier or the whole model by utilizing the few-shot data from the target domain. The comparisons are carried out on one-shot and ten-shot tasks using the CWRU bearing dataset and a cylindrical roller bearing dataset. The experimental result illustrates that our method has good performance on the bearing fault diagnosis across various few-shot conditions. In addition, we found that the pre-training process does not always improve the prediction accuracy

An Improved Point Clouds Model for Displacement Assessment of Slope Surface by Combining TLS and UAV Photogrammetry

TLS can quickly and accurately capture object surface coordinates. However, TLS point clouds cannot cover the entire surface of the target object, due to block of view and limitation of measurement condition. Thus, using it to monitor deformation of slope reduces the detection accuracy of slope surface deformation. To overcome the drawbacks, a method to improve TLS point clouds by UAV photogrammetric point clouds is proposed. The two kinds of point clouds are registered as the new multi-view point clouds by PCA and ICP. The locations of monitoring points are extracted based on HSL color space recognition method from the new multi-view point clouds to analyze the surface displacement. At present, the proposed method has applied in a highway slope in Yunnan Province, and complete point clouds were successfully constructed. A RTK survey was used to compare and verify the proposed method. The verification result demonstrate that the difference of displacement between two measurement methods is less than 10 mm. Comprehensive experiments demonstrate that the proposed method is reliable and meets the slope displacement monitoring standard

Metformin plus L-carnitine enhances brown/beige adipose tissue activity via Nrf2/HO-1 signaling to reduce lipid accumulation and inflammation in murine obesity

This study investigated how Metformin (Met) combined with L-carnitine (L-car) modulates brown adipose tissue (BAT) to affect obesity. High-fat-induced obese rats received daily oral gavage with Met and/or L-car, followed by serum biochemical analysis, histopathological observation on adipose tissues, and immunochemistry test for the abdominal expression of BAT-specific uncoupling protein 1 (UCP1). Mouse-embryonic-fibroblast cells were induced into adipocytes, during which Met plus L-car was added with/without saturated fatty acid (SFA). The role of nuclear factor erythroid 2-related factor 2 (Nrf2) in adipocyte browning was investigated by gene silencing. Mitochondria biogenesis in adipocytes was inspected by Mitotracker staining. Nrf2/heme oxygenase-1 (HO-1)/BAT-related genes/proinflammatory marker expressions in adipose tissues and/or adipocytes were analyzed by Western blot, qRT-PCR, and/or immunofluorescence test. Met or L-car improved metabolic disorders, reduced adipocyte vacuolization and swelling, upregulated levels of BAT-related genes including UCP1 and downregulated proinflammatory marker expressions, and activated the Nrf2/HO-1 pathway in adipose tissues of obese rats. Met and L-car functioned more strongly than alone. In adipocytes, Met plus L-car upregulated BAT-related gene levels and protected against SFA-caused inflammation promotion and mitochondria degeneration, which yet was attenuated by Nrf2 silencing. Met plus L-car enhances BAT activity and white adipose tissue browning via the Nrf2/HO-1 pathway to reduce lipid accumulation and inflammation in obese rats

Potential Activity of Recycled Clay Brick in Cement Stabilized Subbase

Construction waste is one of the products in the process of urbanization. From the perspective of economy and environmental protection, this study used crushed construction waste clay brick to replace the fine aggregate of cement stabilized macadam subbase in certain proportions, and the optimum proportion was obtained according to the unconfined compressive strength of 7 days (d), 28 d, and 90 d. The “modified EDTA titration experiment" was also used to explain how the potential activity of construction waste clay brick works in cement stabilized macadam. The result obtained is that an optimal replacement ratio of 50% exists when using construction waste clay brick to replace the fine aggregate of cement stabilized macadam, and its unconfined compressive strength is higher than that of the 0% replacement ratio specimens; that is, the potential activity of the construction waste clay brick contributes the most to the unconfined compressive strength of the specimens at this proportion. According to the blending method and proportion obtained in this study, the application of construction waste clay bricks in a practical project can maximize environmental protection in road engineering and economic benefits simultaneously