A Simplified Identification Method of Dynamic Stiffness for the Heavy-Load and Low-Speed Journal Bearings

Journal bearing is an essential part of the propulsion shafting system, whose performance directly affects the safety and performance of the shaft and even the entire ship. It is an important, but also a difficult task to obtain the accurate dynamic stiffness values. In order to determine the dynamic characteristics of the journal bearing with specific structural characteristics under specific working conditions, an inverted test platform with multiple sensors for the dynamic stiffness of the heavy-load, low-speed journal bearings (HLLSJBs) was developed, and a novel dynamic test system calibration method was proposed to obtain accurate baseline data, and then the effective characteristic frequency response was gotten based on a refined fast Fourier transform method (RFFT). The present study proposed a simplified identification method to analyze the constitutive relationships between the oil film dynamic parameters and the dynamic stiffness under different rotation and loading conditions in the journal bearing, and then the accurate values of the oil film dynamic stiffness of HLLSJBs were obtained. Furthermore, the values of the structural dynamic stiffness of HLLSJBs were also obtained using a hammer impact method. A comparison with the classic theoretical analysis results reveals that the method proposed is more accurate and effective

BPF Algorithms for Multiple Source-Translation Computed Tomography Reconstruction

Micro-computed tomography (micro-CT) is a widely used state-of-the-art instrument employed to study the morphological structures of objects in various fields. Object-rotation is a classical scanning mode in micro-CT allowing data acquisition from different angles; however, its field-of-view (FOV) is primarily constrained by the size of the detector when aiming for high spatial resolution imaging. Recently, we introduced a novel scanning mode called multiple source translation CT (mSTCT), which effectively enlarges the FOV of the micro-CT system. Furthermore, we developed a virtual projection-based filtered backprojection (V-FBP) algorithm to address truncated projection, albeit with a trade-off in acquisition efficiency (high resolution reconstruction typically requires thousands of source samplings). In this paper, we present a new algorithm for mSTCT reconstruction, backprojection-filtration (BPF), which enables reconstructions of high-resolution images with a low source sampling ratio. Additionally, we found that implementing derivatives in BPF along different directions (source and detector) yields two distinct BPF algorithms (S-BPF and D-BPF), each with its own reconstruction performance characteristics. Through simulated and real experiments conducted in this paper, we demonstrate that achieving same high-resolution reconstructions, D-BPF can reduce source sampling by 75% compared with V-FBP. S-BPF shares similar characteristics with V-FBP, where the spatial resolution is primarily influenced by the source sampling.Comment: 22 pages, 12 figure

Effect of pyrolysis condition on the adsorption mechanism of heavy metals on tobacco stem biochar in competitive mode

Abstract(#br)To clarify the adsorption mechanism of multi-ions on biochars in competitive environment is very important for the decontamination of co-existed heavy metals. Herein, tobacco stem was pyrolyzed in different temperatures with selected residences to obtain biochars with various surface chemistry. Then the adsorption of co-existed typical heavy-metal ions like lead, cadmium, and copper was studied, followed with systematic analysis of surface properties of the post-adsorption biochars. After carefully examining the adsorption performance and surface property alteration of the demineralized biochars, the adsorption mechanism of multi-ions in competitive environment was discovered. Lead showed the most competitive nature with co-existence of cadmium and copper, but the adsorption..