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During the operation of the marine cam–tappet pair, affected by periodic dynamic load, transient velocity, and micromorphology, it usually operates in a mixed lubrication state. Under extreme operational conditions, contact is likely to occur at the asperity of the interface, leading to problems such as stress concentration and dry contact. Considering the transient dynamics and three-dimensional roughness of cam–tappet pair, a mixed-elastohydrodynamic lubrication model is developed in this article, while the effects of surface waviness on the lubrication state are also investigated. The results show that the film thickness can be increased by 0.098 μm, and the coefficient of friction can be reduced by 10.6% when the wavelength ratio ranges from 1/6 to 6. However, when the amplitude exceeds 0.6 μm, the coefficient of friction may reach 0.10. Under conditions of low speed and high load, the film thickness decreases and contact load ratio increases. And about 30% reduction in film thickness is achieved on cam–tappet pair, potentially leading to increased wear or scuffing failure. [ABSTRACT FROM AUTHOR]

The working conditions of cam-tappet pairs in marine diesel engines are directly influenced by the engine output power, the operational speed, the temperature, as well as the components surface micro-morphology, etc., which cause the cam-tappet pairs work in the mixed lubrication state, thus the interfacial friction, pressure and temperature rise are vital to engine performance, efficiency, and durability. An interfacial friction–temperature prediction model for the cam-tappet pairs, considering the effects of transient working conditions and the real surface roughness, is developed in the present study, based on the theories of the transient mixed EHL and the heat transfer under the condition of a fast moving heat source. The numerical results of surface temperature rise are compared with those from the Blok formula, and a good agreement is found. The obtained results show that the presence of 3D roughness may lead to a decrease in the lubricant film thickness, and the surface temperature rise of tappet may exceed 700 K, which is close to the material scuffing temperature, causing the surface failure due to scuffing and wear. If increasing the cam speed and base circle radius within certain range, it may lead to the increment of film thickness and reduction of surface temperature rise, thus the lubrication effectiveness is increased. In addition, using cast aluminum bronze may significantly reduce the surface temperature rise and improve the interfacial characteristics. [ABSTRACT FROM AUTHOR]

In this study, a coupling model is developed to include the aero ball bearing dynamic performance in the mixed thermal elastohydrodynamic lubrication analysis, and the low-speed and heavy-load conditions during start-up and shut-down are involved. Based on the bearing quasi-dynamics, the inside motion state of the main loading surface is obtained, and the mixed thermal elastohydrodynamic lubrication is conducted to get bearing lubrication state and properties. The numerical lubrication model under low-speed and heavy-load conditions is validated against published tested data, which reveal well consistency in central film thickness. The lubrication properties between a single ball and inner race during start-up have been studied, which indicate the lubrication film transforms from boundary lubrication to unsafe mixed thermal elastohydrodynamic lubrication, and then goes into safe lubrication. The lubrication properties of the balls at different azimuths have been investigated during shut-down and compared with those in start-up, which have a similar opposite changing trend, but not a simple invertible process. The time in boundary lubrication region during shut-down is shorter, and the ball number in boundary lubrication region gets less, which means the lubrication properties are relatively better. At last, the parametric study on mixed thermal elastohydrodynamic lubrication properties during shut-down has been carried out. It is found that the small bearing curve coefficient and increasing ball number can reduce the boundary lubrication time and improve the bearing lubrication. [ABSTRACT FROM AUTHOR]

The aim of the present study was to establish a prediction index (PI) model for the 5-year survival rate of patients with hepatitis B-related hepatocellular carcinoma (HCC) after radical resection, and to evaluate the effect of prophylactic transcatheter arterial chemoembolization (TACE). A total of 201 patients with hepatitis B-related HCC who had undergone radical hepatic resection at The First Affiliated Hospital of Xinjiang Medical University (Xinjiang, China) were enrolled, and the clinical, pathological and complete follow-up data were collected. Univariate and multivariate Cox regression analyses were performed to identify which clinicopathological factors were considered significant risk factors and the PI model was established based on these factors. The receiver operating characteristic curve was generated, and the area under the curve (0.841) and the cut-off value for PI were calculated. A Kaplan-Meier plot was used for survival analysis and the log-rank test was used to determine differences in survival. Cox regression analysis demonstrated that there were seven independent factors that may have affected the 5-year survival of HCC patients: Neutrophil-to-lymphocyte ratio (NLR), maximum size of tumor (MTS), tumor histological grade (HG), positive resection margin (PRM), microvascular invasion (MVI), the amount of tumor (AT), and antivirus therapy (AVT). A PI model on 5-year survival was established based on these factors, which was PI=0.32 × NLR + 0.39 × HG (high=1, medium=2, low=3) + 0.92 × PRM (yes=1, no=0) + 0.87 × MVI (yes=1, no=0) + 0.73 × AT (single=0, many=1) + 0.53 × MTS (≥5 cm=1, <5 cm=0)-0.87 × AVT (yes=1, no=0). PI was an independent predictor for survival, with a cut-off value of 2.75. For low-risk patients (PI <2.75), there was no significant difference in cumulative survival between TACE and non-TACE. For high-risk patients (PI >2.75), the cumulative survival rates showed significant differences among patients who had received ≥3 TACE procedues, patients who had received <3 TACE procedures, and patients who had not undergone TACE. The PI model predicts the 5-year survival rate of patients with hepatitis B-related HCC. For high-risk patients with a PI >2.75, if they had received ≥3 prophylactic TACE procedures, they demonstrated a more favorable outcome. For low-risk patients (PI <2.75) with 1 or 2 risk factors, TACE is recommended 1–2 times after surgery. TACE treatment is not required for low-risk patients without any risk fctors. These results may contribute to the decision-making process for whether prophylactic intervention is recommended after radical resection of HCC. [ABSTRACT FROM AUTHOR]