A Uniform Method of Mechanical Disturbance Torque Measurement and Reduction for the Seeker Gimbal in the Assembly Process

In the manufacturing process of seekers, the reduction of disturbance torques (DTs) is a critical but time-consuming work. The innovation of the paper is to present a uniform method to measure and reduce mechanical DTs during gimbal’s assembly process. Firstly, the relationships between assembly parameters and DTs are established and analyzed by theoretical model. And then, a measuring system is established to measure the driven torque of the gimbal’s torque motor. With the goal of stabilizing and minimizing the driven torque, all assembly parameters relating to DTs could be adjusted. Through the proof of a lot of experiments, this proposed method could reduce the bias and fluctuation of these mechanical DTs. This method could also be used for the mechanical DTs reduction of most similar productions and improve the quality and efficiency during their system assembly process

Effects of shrink range and preload on dynamics characteristics of anti-backlash geared rotor-bearing system with composite mesh stiffness

Anti-backlash gear can improve the static transmission precision of system. Besides, the dynamic characteristics of anti-backlash gear system have a significant effect on the performance of overall mechanism, and assembly parameter is an important factor to affect the dynamic characteristic. In order to study the effect of assembly parameter, a single-stage anti-backlash transmission box was taken as an example. Then, the influence of assembly shrink range and preload force on bearing contact stiffness was considered, and the calculation formula of bearing radial stiffness was derived. The calculation method of anti-backlash gear composite mesh stiffness was introduced. Based on this, the transverse-torsion geared rotor-bearing dynamics model and differential equations of anti-backlash gear system with bearing contact stiffness and composite mesh stiffness were proposed. Numerical calculation and the result analysis of frequency sweep show that increasing the shrink range can increase the bearing radial stiffness and further improve the low order resonant frequency (RF) of the system; the effect of inner and outer ring on resonant frequency is equivalent, but neither is obvious. Increasing preload can enhance the bearing radial stiffness and improve the resonant frequency of the system, and the extent of the effect is greater than that of shrink range on the resonant frequency; the effect of preload force on the resonant frequency is obvious

Comparative Analysis of Al-Li Alloy and Aluminum Honeycomb Panel for Aerospace Application by Structural Optimization

Al-Li alloy and aluminum honeycomb panel (AHP) are both excellent materials for aeronautical structures. In this paper, a plate-type aeronautical structure (PAS), which is a base mounting structure for 172 kg functional devices, is selected for comparative analysis with different materials. To compare system-level performance under multidisciplinary constraints, mathematical models for optimization are established and then structural optimization is carried out using Altair OptiStruct. For AHP, its honeycomb core is regarded as orthotropic material and its mechanical properties are calculated by Allen’s model in order to establish finite element model (FEM). The heights of facing sheet and honeycomb core are selected as design variables for size optimization. For Al-Li alloy plate, topology optimization is carried out to obtain its most efficient load path; and then a reconstruction process is executed for practical manufacturing consideration; to obtain its final configuration, accurate size optimization is also used for reconstructed model of Al-Li alloy plate. Finally, the optimized mass and performance of two PASs are compared. Results show that AHP is slightly superior to Al-Li alloy

Immune cell early activation, apoptotic kinetic, and T-cell functional impairment in domestic pigs after ASFV CADC_HN09 strain infection

African swine fever (ASF) caused by the African swine fever virus (ASFV) is a fatal and highly contagious disease of domestic pigs characterized by rapid disease progression and death within 2 weeks. How the immune cells respond to acute ASFV infection and contribute to the immunopathogenesis of ASFV has not been completely understood. In this study, we examined the activation, apoptosis, and functional changes of distinct immune cells in domestic pigs following acute infection with the ASFV CADC_HN09 strain using multicolor flow cytometry. We found that ASFV infection induced broad apoptosis of DCs, monocytes, neutrophils, and lymphocytes in the peripheral blood of pigs over time. The expression of MHC class II molecule (SLA-DR/DQ) on monocytes and conventional DCs as well as CD21 expression on B cells were downregulated after ASFV infection, implying a potential impairment of antigen presentation and humoral response. Further examination of CD69 and ex vivo expression of IFN-γ on immune cells showed that T cells were transiently activated and expressed IFN-γ as early as 5 days post-infection. However, the capability of T cells to produce cytokines was significantly impaired in the infected pigs when stimulated with mitogen. These results suggest that the adaptive cellular immunity to ASFV might be initiated but later overridden by ASFV-induced immunosuppression. Our study clarified the cell types that were affected by ASFV infection and contributed to lymphopenia, improving our understanding of the immunopathogenesis of ASFV

25th annual computational neuroscience meeting: CNS-2016

The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong

Effect of autologous bone marrow-derived mesenchymal stem cells on portal hemodynamics in patients with liver cirrhosis

ObjectiveTo observe the effect of autologous bone marrow-derived mesenchymal stem cells (BMMSCs) on the portal hemodynamics in patients with hepatitis B virus (HBV)-related decompensated cirrhosis. Methods Forty-six patients with HBV-related decompensated cirrhosis, who were admitted to the hospital from February 2011 to January 2012, were divided into treatment group (n=23) and control group (n=23). There were no significant differences in sex, age, diagnosis, biochemical parameters, and imaging findings between the two groups. All patients provided informed consent prior to treatment. Both groups received antiviral, liver-protecting, and diuretic treatment. In addition, in the treatment group, bone marrow (200 ml) was drawn from each patient, BMMSCs were isolated, purified, and cultured, and the cultured cells were processed into cell suspension (10 ml); the cell suspension was injected into the liver via the hepatic artery. After 8 and 12 weeks of treatment, the changes in portal hemodynamic parameters were evaluated. The obtained data were analyzed using SPSS 13.0 software; the paired t test was used for within-group comparisons. ResultsAfter 8 and 12 weeks of treatment, in the treatment group, the diameter of portal vein (DPV) was significantly decreased to 13.26±1.31 mm (t=2.290, P＜0.05) and 12.83±138 mm (t=3.421, P＜0.01), and the diameter of splenic vein (DSV) was significantly decreased to 8.39±1.38 mm (t=2.079, P＜0.05) and 8.02±1.24 mm (t=2.787, P＜0.01); compared with the control group, the treatment group had significantly lower DPV (t=2.382, P＜0.05; t=2.602, P＜0.05) and DSV (t=3.236, P＜0.01; t=4.185, P＜0.01). After 8 and 12 weeks of treatment, in the treatment group, the portal vein maximum velocity (PVX) was significantly increased to 2072±463 cm/s (t=2.833, P＜0.01) and 2058±346 cm/s (t=3.198, P＜0.01); compared with the control group, the treatment group had significantly higher PVX (t=2.530, P＜0.05; t=3.123, P＜0.01). ConclusionAutologous BMMSCs can significantly improve the portal hemodynamics in patients with HBV-related decompensated cirrhosis

Wavelet-based processing for acquisition and transmission of large image data sets using climbing robot to deploy NDT sensors

The thesis describes original work that has developed a novel climbing robot system for the Non-Destructive Testing (NDT) of aircraft fuselage and wings, and the processing and compression ofNDT image data based on the Wavelet Transform. The work establishes the functional requirements for a wall climbing robotic NDT system for aircraft inspection. A climbing robot has been designed and prototyped that can climb on all surface curvatures presented by the fuselage and wings. The novelty in the design is the use of a hierarchy of universal joints to allow flexible adaptation of the robot to varying surface curvatures while at the same time making the structure rigid when suction cups are activated. The structure of the flexible climbing robot has been analysed to establish its intrinsic stability. The hybrid electric and pneumatic control system obtains X-Y movement of the robot and is able to correct off-course errors. The control system tests cylinder rod positions and vacuum pressure before allowing movement of the robot. The climbing robot has been tested successfully on a real aircraft fuselage section. The robot can climb reliably and deploy wet or dry ultrasound transducers with a four axes Cartesian scanner mounted on the climbing robot. The development is reported of a new invention called a regional NDT image compression tool based on the Wavelet Transform. The development includes feature extraction of NDT images and Regional Set Partitioning in Hierarchical Trees (RSPIHT) coding algorithm. With this tool, the NDT image compression showed that the tested images could be compressed at ratios of up to 1000:1, and when the compressed images were reconstructed, the defects could be still observed clearly. This proves that the initial idea of using the regional Wavelet Transform based image compression technique is correct. The results of the work can be used as a general guideline for design and development of other new types of wall-climbing robotic NDT instrumentation and image data processing.EThOS - Electronic Theses Online ServiceGBUnited Kingdo