The reciprocating cutting system is one of the key parts of a tea harvester; and its cutting performance directly determines the cutting power consumption and harvesting quality of the machine. Because the structural parameters of reciprocating cutting systems do not match the tea cut; resulting in larger cutting resistance, it is necessary to optimize the structural parameters. The cricket mouth part has outstanding performance in tea tree fiber cutting; and the curved structural characteristics of the upper jaw of the cricket have been useful to improve the cutting efficiency of cutting system. Quantitative analysis of the structure of the upper jaw revealed that the arc-shaped structure of the incisor lobe would inspire new bionic blades and bionic cutters to solve the above problems. The cutting performance experiment of the cutting blade was designed for investigating the effects of inter-node number; tea variety and blade type (ordinary blade; bionic blade e and bionic blade f) on the cutting force and cutting power consumption. Experimental results of cutting performance have shown that the bionic blade could reduce cutting resistance and cutting power consumption. Tea varieties had little effect on cutting force and cutting power consumption. In addition, the orthogonal test was carried out to study the influence of cutter type with the cutting speed ratio and cutting angle on the integrity rate and missing rate of tea shoot. The field cutting experiment showed that the cutting angle was the most important for the integrity rate and missing rate of tea shoot; followed by the cutter speed ratio; and finally, the cutter type. The optimum combination of parameters was a cutting speed of 0.8 m/s; a forward speed of 1.0 m/s; a cutting angle of −3°, and using the bionic cutter e. With the optimal parameter combination, the integrity rate and missing rate of the tea shoot were 92.7% and 3.9%, which were increased by 13.2% and decreased by 6.4% compared to those under the condition of the 0° cutting angle and an ordinary cutter. As a result, the bionic cutter could obviously reduce cutting resistance; reduce cutting power consumption and improve the harvesting quality. These results would provide guidance for the design of the reciprocating cutting system of tea harvesters and other stalk cutting machinery.
Harvesting is an important procedure for hydroponic lettuces in plant factories. At present, hydroponic lettuces are mainly harvested manually, and the key difficulty in mechanical harvesting is reducing the occurrence of leaf injury. Measuring the size of hydroponic lettuces using the image processing method and intelligently adjusting the operating parameters of the harvesting device are the foundation of high-quality harvesting for lettuces. The overlapped leaves of adjacent hydroponic lettuces cause difficulties in measuring lettuce size, especially the leaves expansion size. Therefore, we proposed an image processing method for measuring lettuce height and leaves expansion size according to the upper contour feature of lettuces and an image included three lettuces. Firstly, the upper contours of the lettuces were extracted and segmented via image preprocessing. Secondly, lettuce height was measured according to the maximum ordinate of the contour. Lastly, the lettuce’s upper contour was fitted to a function to measure the leaves expansion size. The measurement results showed that the maximal relative error of the lettuce height measurements was 5.58%, and the average was 2.14%. The effect of the quadratic function in fitting the upper contour was the best compared with the cubic function and sine function. The maximal relative error of the leaves expansion size measurements was 8.59%, and the average was 4.03%. According to the results of the lettuce height and leaves expansion size measurements, the grabbing parameters of each lettuce were intelligently adjusted to verify the harvesting effect. The harvesting success rates of lettuces was above 90%, and the injured leaves areas of the left, middle, and right lettuces in each image were 192.6 mm2, 228.1 mm2, and 205.6 mm2, respectively. This paper provides a reference for the design and improvement of intelligent harvesters for hydroponic lettuces.
Asymmetric and symmetric cylinder drives are the major actuators for hydraulic linear motion control applications. The asymmetric type is the most popular one and can be found in various areas, industrial, civil and even aerospace. Its compact design in structure and high power to weight ratio are highlighted, but nonlinear behaviours are found in these applications. An asymmetric cylinder is usually controlled by a symmetric ported control valve, which introduces difficulty in the motion control of the cylinder. To avoid such issue, symmetric cylinder drives are typically chosen for high-performance dynamic response applications. This thesis focusses at improving the modelling and driving of the asymmetric cylinder drive system.The major nonlinearities in asymmetric cylinder systems occur when the control valve crosses its null position, causing pressure jumps, and system parameters switching to new values. In this scenario, the system is usually operating at low speed, in which the friction influence is an important factor. In addition, energy efficiency is always a concern in hydraulic applications, a valve-controlled asymmetric cylinder drive can have better controllability than a pump-controlled system, but its energy efficiency is worse than the latter. The aims of this research are to:• Improve modelling of asymmetric cylinder drive systems.• Improve the driving of asymmetric cylinder systems at low speed and velocity reversal with friction consideration.• Combine the advantages of a valve-controlled and a pump-controlled asymmetric cylinder drive system for energy efficiency purpose.A detailed analysis of a valve-controlled asymmetric cylinder system is carried out, and the nonlinearities behaviours are investigated in structure and theory aspects. The simulation modelling in this thesis reveals the system performances when the control valve travels across its null position, and this process is simulated with a numerical solution. An analytical solution is developed, showing that the new analytical solution runs 200 times faster than the original numerical method in simulation. Friction is inevitable in any device and it plays an important role in hydraulic nonlinearities, especially when the system runs at low speed and velocity reversal. Existing friction models are investigated and reviewed, but limited friction models considered the pressure influence in hydraulics. A new friction model for hydraulic system is developed on current LuGre model. This new friction model includes pressure term, acceleration term and velocity term. The new friction model is validated by experimental results and improvements are demonstrated.Under the consideration of energy efficiency, functionality, cost and feasibilities, a hybrid pump-controlled asymmetric cylinder system that combines the merits of a valve-controlled system and a pump-controlled system is implemented. Its pros and cons are investigated and analysed. Its simulation model is built to aid further analysis of the existing nonlinearities.Comparing the simulation results of the hybrid pump-controlled asymmetric cylinder system with the valve-controlled asymmetric cylinder system, the energy efficiency of the hybrid pump-controlled system is 20% better and can be further optimised. The various experimental results validate the simulation model of the hybrid system. Therefore, the functionality and feasibility of the energy efficient design of the hybrid pump-controlled system are validated.The design circuit of the hybrid pump-controlled asymmetric cylinder system is not fully optimised, and improvements can be achieved in future works including replacing the pilot shifted four-way valve with a solenoid valve, adding accumulators to stabilise the pressure in the service line and adding a controller to optimise the system performance.
There are various dependencies in the component-based software systems. ANP can describe the complex structure of system using network representation for system structure. Therefore, it can assign reliability target to each component by comparing the relative importance to the users and considering constraints cost. However, ANP method can only estimate software system reliability statically and indirectly in the design stage. During the service process of software, how to assess the software system reliability, and further to validate the rationality of software reliability allocation in the design stage are dynamic problems, which require a dynamic method. In this paper, firstly, the dynamics model for state changes of software system reliability over time is developed using Petri network, then the software system reliability can be assessed dynamically combined with the dependency graph of components. Finally, the allocation and assessment for component-based software system reliability by ANP combining Petri network is presented and discussed by one example.
Synovial sarcoma (SS), a malignant and uncommon soft tissue sarcoma, typically manifests in the extremities and trunk. However, its occurrence in the infratemporal fossa (ITF) of the head and neck is exceedingly rare. Patients afflicted with SS in this anatomical region pose considerable challenges, as radical surgery is often difficult to undertake, leading to a high rate of postoperative recurrence. Moreover, it is often difficult to effectively control the tumor when the cancer relapses. Much of our understanding regarding SS of ITF stems from limited case reports, with a lack of established clinical guidelines for its management. There exists a significant clinical need for effective therapeutic approaches.
OBJECTIVE: To investigate radiosensitizing effect and mechanism of topotecan (TPT) in human lung adenocarcinoma cell line.METHODS:Radiosensitizing effect was studied by clone forming assays. Cell cycle was analyzed by flow cytometry in the radiation group and the radiation combined TPT group.RESULTS:Cells radiation survival curves were plotted according to single-hit-multi-target model for the radiation group and the radiation combined TPT group. D_0, D_q, and N value were 1.605, 1.734, 2.946 and 1.340, 0.587,1.550, respectively. SERD_0 was 1.2. The number of S-phase cells in the radiation group were higher than that in the control, and elimination of S-phase accumulation appeared in the group with drug application.CONCLUSIONS: TPT has obvious radiosensitizing effect on human lung adenocarcinoma cell line. TPT inhibits repair of radiation damage. TPT is effective in killing cells in S-phase that are highly resistant to ionizing radiation.
The leaves of spinach are delicate and easily injured during harvesting. To reduce the spinach damage rate and increase the conveyance success rate, an orderly harvester was designed and manufactured, and the key conveying parameters of the harvester were optimized by simulation and experiments. The compression damage stress of spinach was determined by compression tests. Then, a finite element simulation model for spinach clamping was established, and the influence of different clamping heights on the spinach deformation and equivalent stress were simulated and analyzed. Finally, response surface Box–Behnken experiments were conducted to optimize the combinations of the twisting angle, clamping distance, and height difference. The results of the compression tests showed that the compression damage stresses of spinach leaves, stems, and their connection points were 8.04 × 10−2 MPa, 7.85 × 10−2 MPa, and 11.63 × 10−2 MPa, respectively. The optimal clamping height of spinach for orderly conveyance was obtained to be 20 mm according to the finite element simulation. The response surface experimental results indicated that the significance order of factors affecting the extrusion force was the clamping distance, the height difference, and the twisting angle. The significance order of factors affecting the conveyance success rate was the clamping distance, the twisting angle, and the height difference. The optimal parameter combination was ae twisting angle of 60°, clamping distance of 24 mm, and a height difference of 20 cm. The experimental validation of the optimization results from the finite element simulation and response surface tests demonstrated that the extrusion force and conveyance success rate were 2.37 N and 94%, respectively, with a conveying damage rate of 3% for spinach, meeting the requirements for the low-damage and orderly harvesting of spinach.
Vulvar carcinoma exhibits a robust correlation alongside HPV infection; however, the impact of HPV rank on the prognostic outcomes of radiation therapy within vulvar malignancies stays ambiguous. In the present study, we performed a comprehensive examination as well as meta-analysis to assess the influence of infection with HPV upon the long-term outlook as well as sensitivity of individuals with vulvar cancer undergoing radiation therapy.
Hybrid pump-controlled asymmetric cylinder drive systems are implemented for energy saving purposes in applications that do not require fast responses. Under low-velocity and low-pressure conditions, the friction influence in the hybrid pump-controlled system is evident. Researchers have developed various models to describe friction. These friction models are implemented based on the relative motion of the contact surfaces, and they can be categorized into static friction and dynamic friction models. For example, dynamic friction models are suitable for simulating the friction in hydraulic cylinder seals under lubrication conditions. Among the dynamic models, the LuGre model can capture almost all static and dynamic friction behaviors at the macroscopic level; for example, stiction, the Stribeck effect, and hysteresis. Thus, the LuGre model is suitable for describing the friction in hydraulic cylinders. Because the friction force in the hydraulic cylinder is mainly from the cylinder seal and seal deformation occurs under pressure due to its flexibility, the friction in a hybrid pump-controlled hydraulic system is affected by the relative motion of the contact surfaces. Therefore, to investigate factors that affect the friction other than the relative motion of the contact surfaces, the friction behaviors of a hybrid pump-controlled hydraulic system are studied. Pressure difference and acceleration terms are introduced in the LuGre friction model, and the simulated friction results of the updated LuGre model are compared with the measured experimental results to validate the new friction model.
A conventional valve-controlled cylinder drive system is not energy efficient, and a pump-controlled cylinder system can be unstable in some particular conditions.For drive systems not requiring fast response, a hybrid pump-controlled system, that combines the advantages of both valve and pump-controlled systems, is proposed.As nonlinear behaviours are inevitable in most asymmetric cylinder drive systems, the hybrid pump-controlled system also suffers from such problems, and extra nonlinear behaviours are identified, for example, stall when the cylinder change its direction of motion.A simulation model of the hybrid pump-controlled asymmetric cylinder drive system is developed and used to investigate the system's simulation behaviours which are analysed and compared with the experimental test results.The energy efficiency of the hybrid pump-controlled system is compared with a comparable valve-controlled hydraulic system with the same hydraulic cylinder sizing.The outcome is to demonstrate the advantage of the hybrid pump-controlled system in energy-saving aspect, and the efficiency of the hybrid system is up to five times more than a conventional hydraulic system.Suggestions are given to improve the performance and stability of the hybrid pump-controlled system.
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