Tribological Aspects of Journal Bearings Focusing on the Stribeck Curve

The dissertation focuses on the frictional characteristics of journal bearings as represented by the Stribeck curve. The behavior of lift-off speed and the factors that affect it are explored. An equation is proposed for predicting the lift-off speed. The comparison between the experimental results of oil- and grease-lubricated journal bearings with a mixed elastohydrodynamic lubrication model for line contacts is indicative of good agreement in the mixed lubrication regime. Efforts are made to modify the surface profile of bushing by putting dimples on its surface. Experimental results show that with proper dimensions of dimples, the friction performance of journal bearings can be improved, particularly for light oils. The friction hysteresis of oil and grease-lubricated journal bearings undergoing oscillatory motion are investigated under different load, with or without oil, oil type, oil inlet temperature, oscillating frequency, and bushing material. A dynamic friction model for infinitely long journal bearing is also developed that demonstrates the existence of hysteresis loop. Finally, a thermal analysis of oscillatory journal bearings is carried out by finite element method using ANSYS. Simulations are found to be in good agreement with experimental measurement of temperature at four locations along the circumference

Uniaxial and triaxial behavior of high strength concrete with and without steel fibers

This study first presents an extensive experimental research program on the true uniaxial and triaxial compression behavior for both high strength concrete (HSC) and steel fiber reinforced high strength concrete (SFHSC). The experimental study mainly focuses on the octahedral shear stress strain relationship of those two types of concrete, which is adopted as the basis to develop a new incremental constitutive model. Emphasis is also put on the investigation of the variation of tangent Poisson\u27s ratio under not only uniaxial but also triaxial stress conditions. The effect of cyclic loading on this parameter is also addressed. According to this research, under triaxial compression, there is no apparent advantage of steel fiber reinforced high strength concrete (SFHSC) over high strength concrete (HSC) in terms of triaxial strength, ductility and stress ~ strain behavior. The compressive meridians and the peak octahedral shear stress (ζoctp) versus peak octahedral shear strain (ϒoctp) relationships for the two types of concrete can be virtually expressed by a single expression respectively. Unlike most of the previous incremental constitutive models, the proposed new model utilizes the experimentally acquired octahedral shear stress (ζotcp) octahedral shear strain (ϒoct) relationship instead of the fictitious concept of equivalent uniaxial strain to locate the peak point of the triaxial stress ~ strain curve, which ensures its capability of simulating the whole load ~ deformation process for both HSC and SFHSC, including the descending branch in the stress ~ strain curve. The results from the model analysis comply with the experimental data fairly well under moderate confining pressures

Effect of propionate on the production of natamycin with Streptomyces gilvosporeus XM-172

This study described the influence of feeding short-chain fatty acids and alcohols on natamycin production in the glucose basal medium, produced by Streptomyces gilvosporeus XM-172. The highest natamycin production was obtained with feeding propionate as compared to other precursors. The optimal propionate concentration and feeding time were 6 g L(-1) and early log phase, respectively. This optimal propionate feeding strategy led to a natamycin production of 6.72 g L(-1), which was nearly 85% higher than that of the control. It was firstly revealed that propionate could greatly promote natamycin biosynthesis by S. gilvosporeus

Synthesis and Characterization of an Amphiphilic Linoleic Acid-g-Quaternary Chitosan with Low Toxicity

A novel amphiphilic derivative of chitosan, namely, a linoleic acid-g-quaternary chitosan (LA-g-QC), was designed and synthesized as low toxic material for biomedical applications in this study. The chemical structure of LA-g-QC was characterized by Fourier transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance (1H-NMR), and elemental analysis. LA-g-QC could form nanosized micelles with self-assembly, which was confirmed by the results of critical micelle concentration (CMC) via fluorescence spectroscopy. The average size of LA-g-QC was 140 nm and its zeta potential was approximately +35.50 mV. CMC value was 31.00 mg/mL. Furthermore, LA-g-QC micelles, at final concentrations between 0.94 μg/mL and 30 μg/mL, did not inhibit the proliferation of HepG2 or SMMC 7721 cell lines. Taken together, LA-g-QC has low cytotoxicity and high potential for the preparation of novel drug-delivery micelles

Serum proteomic, peptidomic and metabolomic profiles in myasthenia gravis patients during treatment with Qiangji Jianli Fang

BACKGROUND: Qiangji Jianli Fang (QJF) has been used for treatment of myasthenia gravis (MG) in China. However, our understanding of the effects of QJF against MG at the molecular level is limited. This study aims to investigate the effects of QJF treatment of MG patients on the protein, peptide and metabolite levels in serum. METHODS: High-throughput proteomic, peptidomic and metabolomic techniques were applied to investigate serum samples from 21 healthy individuals and 47 MG patients before and after QJF treatment via two-dimensional gel electrophoresis, matrix-assisted laser desorption/ionization time of flight mass spectrometry and liquid chromatography Fourier transform mass spectrometry, respectively. RESULTS: After QJF treatment, the expression levels of peptides m/z 1865.019, 2021.128 and 1211.668 of complement C3f increased (P = 0.004, P = 0.001 and P = 0.043, respectively), while that of peptide m/z 1739.931 of component C4b decreased (P = 0.043), in the serum of MG patients. The levels of γ-aminobutyric acid (P = 0.000) and coenzyme Q4 (P = 0.000) resumed their normal states. CONCLUSION: QJF could inhibit the activity of the complement system and restore the normal levels of metabolites

Time Series Adaptive Online Prediction Method Combined with Modified LS-SVR and AGO

Fault or health condition prediction of the complex systems has attracted more attention in recent years. The complex systems often show complex dynamic behavior and uncertainty, which makes it difficult to establish a precise physical model. Therefore, the time series of complex system is used to implement prediction in practice. Aiming at time series online prediction, we propose a new method to improve the prediction accuracy in this paper, which is based on the grey system theory and incremental learning algorithm. In this method, the accumulated generating operation (AGO) with the raw time series is taken to improve the data quality and regularity firstly; then the prediction is conducted by a modified LS-SVR model, which simplifies the calculation process with incremental learning; finally, the inverse accumulated generating operation (IAGO) is performed to get the prediction results. The results of the prediction experiments indicate preliminarily that the proposed scheme is an effective prediction approach for its good prediction precision and less computing time. The method will be useful in actual application

Tunable multiwavelength SOA fiber laser with ultra-narrow wavelength spacing based on nonlinear polarization rotation

A tunable multiwavelength fiber laser with ultra-narrow wavelength spacing and large wavelength number using a semiconductor optical amplifier (SOA) has been demonstrated. Intensity-dependent transmission induced by nonlinear polarization rotation in the SOA accounts for stable multiwavelength operation with wavelength spacing less than the homogenous broadening linewidth of the SOA. Stable multiwavelength lasing with wavelength spacing as small as 0.08 nm and wavelength number up to 126 is achieved at room temperature. Moreover, wavelength tuning of 20.2 nm is implemented via polarization tuning