The robotic drilling is receiving considerable attention and eliciting widespread interest in aircraft assembly. However, the drilling end-effector with serial mechanism has better kinematics performance but worse dynamic performance. A robotic drilling end-effector based on 3-SPR parallel mechanism is proposed and afterward its normal adjustment is dynamically modeled. A sliding mode variable structure controller based on component reaching law is proposed for its normal adjustment control, simulation experiment is carried out on this designed end-effector and the simulation results show that the presented control scheme has strong robustness and adaptiveness to the non-linear factors such as non-determinacy of model and system parameter variations.
Neurosurgery is widely used in clinical application.As the key neurosurgery assistive technology for neurosurgery,neural monitoring is used to real-time accurately monitor neural state and effectively prevent nerve injury.In this paper,an SOPC-based neural monitoring system is presented.This system integrates analog circuits with digital circuits and cooperate hardware circuits with NIOS II embedded software.To optimize the system,ping-pong operation,serial to parallel conversion and pipeline are employed.The function of system is tested by embedded logic analyzer.It is showed that the system sequence,data conversion and transmission are normal.The whole design is completed on a Cyclone III-based development board,DE 0.The resource consumption is 7 516 logic elements and the maximum hardware-work-frequency could achieve 125.74 MHz while the software-work-frequency is 119.76 MHz.
The extreme microorganisms Ferroplasma spp., play an important role in bioleaching of sulphide ores at low pH value and temperatures around 50 degrees C. Without cell wall, Ferroplasma spp. is sensitive to pulp density, shearing force and heavy metal ions. Thus it is difficult to obtain their high cell density cultures, which limits the large-scale industrial application. In this paper, the optimum culture conditions of Ferroplasma thermophilum were studied by shaking culture. The results showed that the optimum culture conditions are as follows: 50 degrees C, initial pH 0.5, 50 mL working volume in 250 mL shaking-flask, inorganic nitrogen source (NH4)2SO4. The optimum combination of FeSO4.7H2O, yeast extract and peptone was determined by orthogonal experiments, including FeSO4.7H2O 40 g/L, yeast extract 0.3 g/L, peptone 0.2 g/L. Under the optimum culture conditions, the cell density was up to 6.3 x 10(7) cell/mL, and the oxidation of 40 g/L ferrous sulfate heptahydrate was finished in less than 72 hours. The results might provide information for scale-up of archaeon culture as well as its industrial application.
The aim of this study is to develop and assess the peg transfer training module face, content and construct validation use of the box, virtual reality (VR), cognitive virtual reality (CVR), augmented reality (AR), and mixed reality (MR) trainer, thereby to compare advantages and disadvantages of these simulators. Training system (VatsSim-XR) design includes customized haptic-enabled thoracoscopic instruments, virtual reality helmet set, endoscope kit with navigation, and the patient-specific corresponding training environment. A cohort of 32 trainees comprising 24 novices and 8 experts underwent the real and virtual simulators that were conducted in the department of thoracic surgery of Yunnan First People’s Hospital. Both subjective and objective evaluations have been developed to explore the visual and haptic potential promotions in peg transfer education. Experiments and evaluation results conducted by both professional and novice thoracic surgeons show that the surgery skills from experts are better than novices overall, AR trainer is able to provide a more balanced training environments on visuohaptic fidelity and accuracy, box trainer and MR trainer demonstrated the best realism 3D perception and surgical immersive performance, respectively, and CVR trainer shows a better clinic effect that the traditional VR trainer. Combining these in a systematic approach, tuned with specific fidelity requirements, medical simulation systems would be able to provide a more immersive and effective training environment.
The author analyzed the working characteristics of special turbine for cooling tower basing on the difference between the special turbine and the conventional hydraulic turbine. This paper points out that the special turbine works in a pressure water system and has typical ultra-low specific speed characteristic. These characteristics determine the type and parameters selection of the special turbine. Based on the theory the author has designed some special turbines in many projects in China. The practical operation shows that the turbines have high energy conversion efficiency and are steady in operation, with fairly good matching of the fans.
It has been proved that arbitrarily high-energy collision between two particles can occur near the horizon of an extremal Kerr black hole as long as the energy $E$ and angular momentum $L$ of one particle satisfies a critical relation, which is called the BSW mechanism. Previous researchers mainly concentrate on geodesic motion of particles. In this paper, we will take spinning particle which won't move along a timelike geodesic into our consideration, hence, another parameter $s$ describing the particle's spin angular momentum was introduced. By employing the Mathisson-Papapetrou-Dixon equation describing the movement of spinning particle, we will explore whether a Kerr-Sen black hole which is slightly different from Kerr black hole can be used to accelerate a spinning particle to arbitrarily high energy. We found that when one of the two colliding particles satisfies a critical relation between the energy $E$ and the total angular momentum $J$, or has a critical spinning angular momentum $s_c$, a divergence of the center-of-mass energy $E_{cm}$ will be obtained.
The design of output feedback controllers that eliminate uncertainties caused by critical races in asynchronous sequential machines is considered. The objective is to build controllers that drive a race-afflicted machine so as to match a prescribed deterministic model. Necessary and sufficient conditions for the existence of such controllers are presented in terms of a numerical matrix derived from the given machine. When controllers exist, an algorithm for their construction is also provided. The discussion depends on the novel notion of ‘generalised state’, which helps represent the uncertainty created by critical races and facilitates the construction of controllers.
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