Discrete Element Simulation Based on Elastic–Plastic Damping Model of Corn Kernel–Cob Bonding Force for Rotation Speed Optimization of Threshing Component

Current corn kernel-cob bonding mechanics models (LSD models) uniformly consider the bonding force changes during the maize threshing operation as an elastic change, resulting in computational errors of up to 10% or more in discrete element simulations. Due to the inability to perform high-precision discrete element simulation of the mechanics characteristics during the corn threshing operation, the core operating parameters of the corn thresher (rotation speed of the threshing component) rely mainly on empirical settings, resulting in a consistent difficulty in exceeding 85% of the corn ear threshing rate. In this paper, by testing the mechanics characteristics of corn kernels, the bonding force is found to have both elastic and plastic changes during the threshing process. An elastic–plastic (EP) damping model of the corn kernel–cob bonding force was established by introducing a bonding restitution coefficient e to achieve an integrated consideration of the two changes. By testing the relationship between the properties of the corn ear itself and the model parameters, the pattern of the effect of the corn ear moisture content and the loading direction of the ear by force on the EP model parameters was found. By establishing a model of the relationship between the corn cob’s own properties and the model parameters, the EP model parameter values can be determined by simply determining the moisture content of the ear. In this paper, the EP model was established and the high-precision simulation and analysis of the process of bonding force variation between corn kernel and cob is realized on the self-developed AgriDEM software. At the meantime, the optimal values of the threshing component rotation speed under different conditions of moisture content of corn ear were obtained by establishing an optimization model of threshing component rotation speed. The test results showed that the corn ear threshing rate could reach more than 92.40% after adopting the optimized speed value of the threshing component in this paper. Meanwhile, the test results showed that the discrete element simulation results based on the EP model did not significantly differ from the measured results of the thresher. Compared with the most widely used LSD model, the EP model can reduce the computational error by 3.35% to 6.05%.

A comparison of femoral component rotation after total knee arthroplasty in Kanekasu radiographs, axial CT slices and 3D reconstructed images

Objective To compare the posterior condylar angle measured with Kanekasu radiograph and 2D-CT with the gold standard 3D-CT following primary total knee arthroplasty (TKA). Methods Eighty-two knees with pain following TKA were included in this retrospective study. Two independent raters measured the anatomical and surgical posterior condylar angles twice on each Kanekasu radiograph and 2D-CT. These measurements were compared against the 3D-CT measurement. The intra- and interrater reliability of the Kanekasu radiograph and 2D-CT and the correlation with 3D-CT were calculated. Results The intra- and interrater reliability for measurements of the anatomical posterior condyle angle for the Kanekasu radiograph and the 2D-CT were excellent for both raters (0.85–0.92). For the less experienced rater 1, the intrarater reliability was significantly better for 2D-CT than Kanekasu radiograph for measuring both the surgical (p < 0.01) and anatomical posterior condyle angles (p < 0.05). For the experienced rater 2, the intrarater reliability was significantly better for Kanekasu radiograph than 2D-CT for measurement of the surgical posterior condyle angle (p < 0.05). The correlation with 3D-CT is higher in 2D-CT than in Kanekasu radiograph (p < 0.01). While the Kanekasu radiograph predicts the 3D-CT angle with 65.9%, 2D-CT can measure the true angle with 82.9% certainty. Conclusion Measurements using the anatomical transepicondylar axis are easier to replicate compared to the surgical transepicondylar axis. In comparison with the gold standard 3D-CT, 2D-CT showed a significantly higher correlation with 3D-CT than the Kanekasu measurements. If 3D-CT is available, it should be preferred over 2D-CT and Kanekasu view radiograph for femoral component rotation measurements.

The Effect of Coronal and Axial Femoral Component Rotation on Midflexion Laxity and Patient Reported Outcomes in Total Knee Arthroplasty

Joint balance in total knee arthroplasty (TKA) has traditionally focused on achieving a tight symmetric extension gap and rectangular or trapezoidal gaps in flexion. This study sought to investigate the effect of femoral and tibial coronal rotation and femoral axial rotation on midflexion coronal joint balance and patient outcomes.A prospective multi-center study was performed with a mixture of tibia-first gap-balancing and femur-first approaches were performed using the Corin OMNIBotics robot-assisted TKA platform with APEX implant components. Coronal and axial femoral and tibial resections were recorded by the platform. Medial and lateral joint gaps were recorded while applying a computer-controlled load to the joint throughout flexion during trialing using the Corin BalanceBot device. In addition, 1-year Knee Injury and Osteoarthritis Outcome Score (KOOS) and PROMIS-10 global health scores were collected.231 surgeries were identified: 66.9±8.1 years, 31.4±4.8 kg/m2 and 57% female (121) with a mean pre-operative HKA angle of 4.5±5.2° varus. A significant correlation was found between the medio-lateral (ML) joint gap difference in midflexion and both extension and flexion joint line (p=0.003, r2=-0.20, p=0.001, r2=-0.22, respectively). A significant correlation was found between midflexion ML imbalance and KOOS stiffness questions at 3 M and 6 M post-op (r2=-0.15, p=0.036, r2=-0.18, p=0.013), in which a more balanced knee correlated with improved outcomes.Treating flexion and extension joint balance in isolation may not capture the effect on midflexion laxity. Component placement should take in to account the effect on joint gaps throughout flexion to target optimal joint balance.