Qinghua Yang

Design and experiment of the negative pressure adsorption Cartesian robot system for apple harvesting

Reduction is a crucial stage in the surgical treatment of bone fractures.The detailed fracture information of the patient can be obtained from computed tomography (CT) scans before surgery and enable physicians to plan preoperative reduction, to reduce the operation time and thus increase the probability of getting satisfactory results. The primary purpose of this paper is to design a computer-aided automatic registration method of fracture point cloud data, so as to simplify the fracture reduction process. In this paper, we propose an integrated fracture reduction system was introduced. The system enables direct semi-automatic processing from CT images to fracture reduction. First, a 3D fracture models is reconstructed from CT images by using the modified Marching Cube (MC) algorithm and is discretized to generate a point cloud. Second, the K-dimensional (KD) tree algorithm is used to cluster and segment the point clouds to identify different fracture fragments. Last, through the combination algorithm of Normal Distributions Transform(NDT) and modified Iterative Closest Point(ICP), the coarse alignment and fine registration of point clouds are achieved step by step. This method has been successfully applied to the reduction of tibial fracture. In the tests performed, the processing time of each step, the point cloud and the 3D model after registration are displayed. The semi-automatic integrated system based on preoperative CT scanning is used to realize fracture reduction，which provides a feasible foundation for minimally invasive and accurate fracture reduction surgery.

Working state classification, which is a critical part of an asynchronous control system based on a brain-computer interface (BCI). The traditional algorithms for the working state classification are based on the threshold of power spectral density (PSD) or the canonical correlation analysis (CCA) parameters, which usually suffer insufficient robustness in case of using one threshold. To improve the robustness of working state classification, a multi-parameter asynchronous working state classification method combined with a genetic algorithm (GA-PSD-CCA) is proposed based on SSVEP. GA-PSD-CCA obtains the CCA parameter and the PSD parameter from the processed electroencephalogram (EEG) signals. Then GA-PSD-CCA iteratively searches the optimization of the PSD and CCA parameters and finds the threshold value by the genetic algorithm for the working state classification to recognize the working state. An experiment is designed to compare the application effect of GA-PSD-CCA with the traditional algorithm based on the EEG signals of ten subjects. The results show that the average accuracy with GA-PSD-CCA achieved 89.35% ± 8.39% and has an improvement of more than 7% compared with the traditional algorithm which has the highest accuracy. GA-PSD-CCA has a large improvement in asynchronous working state classification accuracy and achieves high target recognition accuracy. The BCI systems with the GA-PSD-CCA will have lower false recognition of commands and higher reliability and smoothness of state recognition processes.

Objective: Dynamization of the external fixator, defined as gradually decreasing construct‐stability of the fixator, is widely accepted as a method for treatment during the late phase of the bone healing process. However, the dynamization is mostly based on the subjective experience of orthopaedists at present, without unified standards and a clear theoretical basis. The objective of the study is to investigate the influence of the dynamization operations on the tibial mechanical properties with a hexapod circular external fixator and standardize the dynamization process.Methods: A 3D‐printed tibial defects model with Young's modulus of 10.5 GPa and Poisson's ratio of 0.32 simulated the clinically fractured bone. A 10 × ∅ 45 mm silicone sample with Young's modulus of 2.7 MPa and Poisson's ratio of 0.32 simulated the callus in the fracture site. Furthermore, a hexapod circular external fixator whose struts were coded from #1 to #6 was fixed on the model with six half‐pins (5 mm diameter). Corresponding to the action of removing and loosening the struts, 17 dynamization operations are designed. For each construct after different dynamization operations, the mechanical environment changes in the fracture site were recorded by a triaxle forces sensor under gradually increasing external load from 0 to 500 N.Results: The results show that the bone axial load‐sharing ratio of each construct in the removal group was generally higher than that in the loosening group. The ratio increased from 92.51 ± 0.74% to 102.68 ± 0.27% with the number of operated struts rising from 2 to 6. Besides, the constructions with the same number of operated struts but with different strut codes such as constructions 3–5, had similar bone axial load‐sharing ratios. In addition, the proposed dynamization method of the hexapod circular external fixator can gradually increase the bone axial load‐sharing ratio from 90.73 ± 0.19% to 102.68 ± 0.27% and maintain the bone radial load‐sharing ratio below 8%.Conclusion: The laboratory study verified the effects of the type of operations and the number of operated struts on the bone axial load‐sharing ratio, as well as the slight influence of the choice of the strut code. Besides, a dynamization method of the hexapod circular external fixator was proposed to increase the bone axial load‐sharing ratio gradually.

A patient with chief complaint of bilateral progressive visual impairment was diagnosed with Fuchs corneal dystrophy (FECD) in both eyes, macular hole in the left eye, and intraocular lens eye in the right eye. After communication with the patient and his family, they agreed to receive Descemet's stripping without endothelial keratoplasty (DWEK) in the left eye. One year after the operation, the cornea of the left eye was transparent, and the central posterior elastic layer was missing about 4.0 mm diameter. The naked vision of left eye was 0.1, and the correction was not improved. It can be seen that DWEK surgery has a good therapeutic effect on patients with mild FECD.

Understanding multiphase flow and gas transport occurring in electrodes is crucial for improving the performance of proton exchange membrane fuel cells. In the present study, a pore-scale model using the lattice Boltzmann method (LBM) was proposed to study the coupled processes of air–water two-phase flow and oxygen reactive transport processes in porous structures of the gas diffusion layer (GDL) and in fractures of the microscopic porous layer (MPL). Three-dimensional pore-scale numerical results show that the liquid water generation rate is gradually reduced as the oxygen consumption reaction proceeds, and the liquid water saturation in the GDL increases, thus the constant velocity inlet or pressure inlet condition cannot be maintained while the results showed that at t = 1,200,000 iterations after 2900 h running time, the local saturation at the GDL/MPL was about 0.7, and the maximum value was about 0.83, while the total saturation was 0.35. The current density reduced from 2.39 to 0.46 A cm⁻². Effects of fracture number were also investigated, and the results showed that for the fracture numbers of 8, 12, 16, and 24, the breakthrough point number was 4, 3, 3, and 2, respectively. As the fracture number increased, the number of the water breakthrough points at the GDL/GC interface decreased, the liquid water saturation inside the GDL increased, the GDL/MPL interface was more seriously covered, and the current density decreased. The pore-scale model for the coupled multiphase reactive transport processes is helpful for understanding the mechanisms inside the porous electrodes of PEMFC.