Total knee replacement is a common surgical procedure in orthopaedics. Accurate volumetric wear assessment of the polyethylene knee inserts has been an essential subject for improving the longevity. A new CMM-based methodology was presented to determine volumetric material loss based on curve surface fitting without prewear data, CAD model, or original design of drawings. Both computational and experimental simulated volume removal tests were run to validate the methodology by comparing with the gravimetric measurements. The volume and linear wear of the tibial inserts were calculated using the presented method based on the coordinates acquired by the CMM. The results indicate that the methodology is adequate for clinically retrieved tibial inserts where no prewear data are provided. This technique can also be used for biotribological study of other polyethylene components, since wear and damage can be assessed visually and volumetrically.
Ultrahigh molecular weight polyethylene (UHMWPE) bearings are used widely in orthopaedic joint replacement as a prominent material for improving the longevity, which is dramatically influenced by wear of polyethylene. Polyethylene tibial knee components from knee simulators under two different input conditions were analyzed using CMM and Micro-CT measurement techniques for volumetric loss with gravimetric measurement as reference. Based on the coordinates and image slices obtained, the surface curve fitting and image digitization methodology were used for the creation of nominal "original" surface in the case of no prewear data provided. The comparison results indicate that gravimetric remains the gold standard and the CMM measurement took less time and had better precision, accuracy, and repeatability compared to Micro-CT measurement technique.
Abstract. The data transfer rate is the traditional criterion for evaluating the overall performance of a hard disk. In this paper, the data transmission performance of hard disk was characterized based on fractal theory. The traditional mechanical hard disks and solid state disks with different capacities and specifications were tested and the corresponding signal graph of data transfer was analysed for the calculation of fractal dimension D. The results indicate that the process of hard disk data transfer has fractal characteristics; the fractal dimension D increases with the increase of the average transfer rate and the rotating speed of mechanical hard disk. However, there seems no direct correspondence between the fractal dimension D and the capacity of the hard disk; the larger the floating range of data transmission, the greater value of fractal dimension D.
As the core content of state-owned enterprises reform, Chinese state-owned enterprises have some problems in corporate governance for a long time, which restricts the process of the reform and development in these enterprises. As a breakthrough in deepening the reform of state-owned enterprises, the mixed-ownership reform has opened up a new theoretical research direction and reform practice space for state-owned enterprises to carry out and improve corporate governance. Under the framework of corporate governance and contemporary property rights theory and based on the analysis of the characteristics and existing problems of corporate governance in Chinese state-owned enterprise groups, this paper summarizes the framework and specific measures that can be taken by state-owned enterprises to improve corporate governance under mixed-ownership reform.
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