A Review on Rolling Bearing Fault Signal Detection Methods Based on Different Sensors.

As a precision mechanical component to reduce friction between components, the rolling bearing is widely used in many fields because of its slight friction loss, strong bearing capacity, high precision, low power consumption, and high mechanical efficiency. This paper reviews several excellent kinds of study and their relevance to the fault detection of rolling bearings. We summarize the fault location, sensor types, bearing fault types, and fault signal analysis of rolling bearings. The fault signal types are divided into one-dimensional and two-dimensional images, which account for 40.14% and 31.69%, respectively, and their classification is clarified and discussed. We counted the proportions of various methods in the references cited in this paper. Among them, the method of one-dimensional signal detection with external sensors accounted for 3.52%, the method of one-dimensional signal detection with internal sensors accounted for 36.62%, and the method of two-dimensional signal detection with external sensors accounted for 19.72%. The method of two-dimensional signal detection with internal sensors accounted for 11.97%. Among these methods, the highest detection rate is 100%, and the lowest detection rate is more than 70%. The similarities between the different methods are compared. The research results summarized in this paper show that with the progress of the times, a variety of new and better research methods have emerged, which have sped up the detection and diagnosis of rolling bearing faults. For example, the technology using artificial intelligence is still developing rapidly, such as artificial neural networks, convolutional neural networks, and machine learning. Although there are still defects, such methods can quickly discover a fault and its cause, enrich the database, and accumulate experience. More and more advanced techniques are applied in this field, and the detection method has better robustness and superiority.

Semi-rational mutagenesis of an industrial Streptomyces fungicidicus strain for improved enduracidin productivity.

The biosynthesis of the valuable antibiotic enduracidin by Streptomyces fungicidicus TXX3120 is a complex multistep process. To identify the rate-limiting step of the entire biosynthetic process, we carried out a deep RNA sequencing towards the mycelia of TXX3120 at different fermentation stages. Comparative RNA-seq analysis indicated that the expression level of the endC gene during the enduracidin production phase was evidently lower than that of the other relevant genes to enduracidin biosynthesis. This result was further confirmed by quantitative RT-PCR, and the giant non-ribosomal peptide synthase (NRPS) encoded by endC was predicated to be the rate-limiting enzyme in enduracidin biosynthesis. To increase the expression of endC during the enduracidin production phase, a reporter-based selection system was developed by genetically replacing the initial part of the endC gene with a thiostrepton resistance gene (tsr), which will then act as a selectable marker to report the expression level of the rate-limiting gene endC, thereby facilitating the selection of enduracidin-overproducing mutants following random mutagenesis. After one round of mutagenesis, thiostrepton resistance selection, and restoration of the endC gene, three mutant strains with improved endC expression levels were obtained. Their highest enduracidin titers reached 9780.54, 9272.46, and 8849.06 U/mL, respectively representing 2.31-, 2.19-, and 2.09-fold of the initial industrial strain TXX3120. Our research provides a useful strategy for the rational breeding of industrial strains that synthesize complex natural products.

Ficellomycin: an aziridine alkaloid antibiotic with potential therapeutic capacity.

Ficellomycin is an aziridine antibiotic produced by Streptomyces ficellus, which displays high in vitro activity against Gram-positive bacteria including multidrug resistant strains of Staphylococcus aureus. Compared to currently available antibiotics, ficellomycin exhibits a unique mechanism of action-it impairs the semiconservative DNA replication by inducing the formation of deficient 34S DNA fragments, which lack the ability to integrate into larger DNA pieces and eventually the complete bacterial chromosome. Until recently, some important progress has been made in research on ficellomycin synthesis and biosynthesis, opening the perspective to develop a new generation of antibiotics with better clinical performance than the currently used ones. In this review, we will cover the discovery and biological activity of ficellomycin, its biosynthesis, mode of action, and related synthetic analogs. The role of ficellomycin and its analogs as an important source of drug prototypes will be discussed together with future research prospects.

Analysis of straight conjugate internal gear pump through numerical modeling and experimental validation.

As a medium and low pressure gear machine without automatic compensation structure for axial and radial clearances, the friction pairs in the straight conjugate internal gear pumps (SCIGPs) depend on the fixed small clearances to seal, lubricate and transfer the force. The oil film design of the friction pairs has become an important part of gear pump design. However, there has never been a publicly published research on the oil film design of the SCIGP in past literature. This paper applies orthogonal test to the oil film design of the SCIGP for the first time to determine the best working clearances. With this goal, the paper first provides the mathematical models for analyzing the internal leakage flow and the viscous friction loss, which elucidate the relationships between the leakage and the friction loss with working conditions. After that, the orthogonal test scheme for numerical simulation was designed on the basis of determining the range of oil film thickness. The paper also propounds the viewpoints of using the range-method to estimate the primary and secondary relationship of factors and determining the optimal combination according to the test target. Based on this concept, the main factors affecting the target are procured and the optimal working clearances of the friction pairs are determined. For the purpose of verifying the model, the redesigned prototype was tested and compared with the simulation results. The results validate the applicability of the simulation model and the correctness of the simulation method. Finally, the paper summarizes the ways to improve the total efficiency and the working conditions at the highest efficiency.

Central pattern generator-based coupling control method for synchronously controlling the two-degrees-of-freedom robot.

Synchronous control is a fundamental and significant problem for controlling a multi-joint robot. In this article, by applying two coupled Rayleigh oscillators as the referred central pattern generator models for the two joints of a two-degrees-of-freedom robot, the central pattern generator-based coupling control method is proposed for controlling the two-degrees-of-freedom robot's joints. On these bases, the co-simulation model of the two-degrees-of-freedom robot with the proposed central pattern generator-based coupling control method is established via ADAMS and MATLAB/Simulink, and the performance of the central pattern generator-based coupling control method on synchronizing two motions of two-degrees-of-freedom robot's joints is numerically simulated. Furthermore, the experimental setup of a two-degrees-of-freedom robot is established based on the real-time simulations system via the proposed central pattern generator-based coupling control method. And experiments are carried out on the established setup. Simulations and experimental results show that the phase of the controlled two-degrees-of-freedom robot's joints is mutual locked to other, and their motion pattern can be adjusted through the coupling parameter in the central pattern generator-based coupling control method. In conclusion, the proposed central pattern generator-based coupling control method can control the two-degrees-of-freedom robot's joints to produce the coordinated motions and adjust the rhythmic pattern of the two-degrees-of-freedom robot.

Engineered variants of a lipase from Yarrowia lipolytica with improved trypsin resistance for enzyme replacement therapy.

To improve the proteolytic stability of the lipase LIP2 from Yarrowia lipolytica, the peptide bonds susceptible to trypsin in LIP2 were analyzed by tandem mass spectrometry and redesigned by site-directed mutagenesis. Different variants of the enzyme were expressed in Pichia pastoris GS115 and their biochemical properties were subsequently investigated. Although most of the variants were still cleaved by trypsin, some of them did show an evident increase of resistance against proteolytic degradation. The most stable mutant was LIP2-C5, in which five trypsin-cleavage sites were replaced by non-preferred amino acids. Upon incubation with human trypsin for 80 min at 37°C, the mutant LIP2-C5 was found to retain >70% of its initial activity, compared to only 10% for the wild-type.

A 5 g Inertial Micro-Switch with Enhanced Threshold Accuracy Using Squeeze-Film Damping.

Our previous report based on a 10 g (gravity) silicon-based inertial micro-switch showed that the contact effect between the two electrodes can be improved by squeeze-film damping. As an extended study toward its potential applications, the switch with a large proof mass suspended by four flexible serpentine springs was redesigned to achieve 5 g threshold value and enhanced threshold accuracy. The impact of the squeeze-film damping on the threshold value was theoretically studied. The theoretical results show that the threshold variation from the designed value due to fabrication errors can be reduced by optimizing the device thickness (the thickness of the proof mass and springs) and then establishing a tradeoff between the damping and elastic forces, thus improving the threshold accuracy. The design strategy was verified by FEM (finite-element-method) simulation and an experimental test. The simulation results show that the maximum threshold deviation was only 0.15 g, when the device thickness variation range was 16⁻24 µm, which is an adequately wide latitude for the current bulk silicon micromachining technology. The measured threshold values were 4.9⁻5.8 g and the device thicknesses were 18.2⁻22.5 µm, agreeing well with the simulation results. The measured contact time was 50 µs which is also in good agreement with our previous work.

Stable and Controllable Synthesis of Silver Nanowires for Transparent Conducting Film.

Silver nanowires without particles are synthesized by a solvothermal method at temperature 150 °C. Silver nanowires are prepared via a reducing agent of glycerol and a capping agent of polyvinylpyrrolidone (M w ≈ 1,300,000). Both of them can improve the purity of the as-prepared silver nanowires. With controllable shapes and sizes, silver nanowires are grown continuously up to 10-20 µm in length with 40-50 nm in diameter. To improve the yield of silver nanowires, the different concentrations of AgNO3 synthesis silver nanowires are discussed. The characterizations of the synthesized silver nanowires are analyzed by UV-visible absorption spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscope (AFM), and silver nanowires are pumped on the cellulose membrane and heated stress on the PET. Then, the cellulose membrane is dissolved by the steam of acetone to prepare flexible transparent conducting thin film, which is detected 89.9 of transmittance and 58 Ω/□. Additionally, there is a close loop connected by the thin film, a blue LED, a pair of batteries, and a number of wires, to determinate directly the film if conductive or not.