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Abstract Background The present study aimed to investigate the genetic polymorphisms in exon 4 of the NOD2 gene in tuberculosis patients and healthy controls, in order to clarify whether polymorphisms in the NOD2 gene is associated with tuberculosis. Methods A case-control study was performed on the Chinese Han, Uygur and Kazak populations. Exon 4 of the NOD2 gene was sequenced in 425 TB patients and 380 healthy controls to identify SNPs. Results The frequency of T/G genotypes for the Arg587Arg (CGT → CGG) single nucleotide polymorphism (SNP) in NOD2 was found to be significantly higher in the Uygur (34.9%) and Kazak (37.1%) populations than the Han population (18.6%). Also, the frequency of G/G genotypes for the Arg587Arg SNP was significantly higher in the Uyghur (8.3%) and Kazak (5.4%) populations than the Han population (0.9%). Meanwhile, no significant difference was found in the Arg587Arg polymorphism between the tuberculosis patients and healthy controls in the Uyghur and Kazak populations (P > 0.05) whereas, a significant difference was observed in the Arg587Arg polymorphism between the tuberculosis patients and healthy controls in the Han population (P < 0.01). The odd ratio of 2.16 (95% CI = 1.31-3.58; P < 0.01) indicated that the Arg587Arg SNP in NOD2 may be associated with susceptibility to tuberculosis in the Chinese Han population. Conclusions Our study is the first to demonstrate that the Arg587Arg SNP in NOD2 is a new possible risk factor for tuberculosis in the Chinese Han population, but not in the Uyghur and Kazak populations. Our results may reflect racial differences in genetic susceptibility to tuberculosis.

The complex influence of various disturbances on an inertially stabilized platform (ISP) restricts the further improvement of its servo performance. This article investigates the mapping relationship between internal and external disturbances and servo performance by establishing a high-precision dynamics model of the servo device with simulation and experiment. For internal disturbances, a nonlinear model of friction and backlash is established based on a BP neural network, and the transmission error is reconstructed based on the principle of main order invariance. For external disturbances, the road disturbance torque, changing inertia, and mass imbalance torque are modeled. The quantitative mapping relationship between internal and external disturbances and servo performance is obtained through simulation, in which friction and road disturbance are the largest internal and external factors affecting the servo performance, respectively. These conclusions are verified by load simulation experiments on a certain type of servo device, in which the servo performance is improved by 17% for every 25% reduction of friction torque, and the servo performance is reduced by 12% for every 33% increase of road disturbance torque. The research results provide a reference for servo device selection, performance indicator assignment, and performance prediction of the ISP. [ABSTRACT FROM AUTHOR]

Electro-optical detection systems face numerous challenges due to the complexity and difficulty of targeting controls for "low, slow and tiny" moving targets. In this paper, we present an optimal model of an advanced n-step adaptive Kalman filter and gyroscope short-term integration weighting fusion (nKF-Gyro) method with targeting control. A method is put forward to improve the model by adding a spherical coordinate system to design an adaptive Kalman filter to estimate target movements. The targeting error formation is analyzed in detail to reveal the relationship between tracking controller feedback and line-of-sight position correction. Based on the establishment of a targeting control coordinate system for tracking moving targets, a dual closed-loop composite optimization control model is proposed. The outer loop is used for estimating the motion parameters and predicting the future encounter point, while the inner loop is used for compensating the targeting error of various elements in the firing trajectory. Finally, the modeling method is substituted into the disturbance simulation verification, which can monitor and compensate for the targeting error of moving targets in real time. The results show that in the optimal model incorporating the nKF-Gyro method with targeting control, the error suppression was increased by up to 36.8% compared to that of traditional KF method and was 25% better than that of the traditional nKF method. [ABSTRACT FROM AUTHOR]

Friction is a complex nonlinear behavior and a significant factor that limits the performance improvement of servo systems. Drawing inspiration from the particular prestiction friction phenomenon exhibited by direct-drive systems upon sudden emergency stops, this paper introduces a dynamic and continuous friction model that includes pre-sliding and gross-sliding regimes. By analyzing the friction dynamics when the system velocity briefly reaches zero, a concave function related to the previous state of the system is used to describe the transition of friction in the pre-sliding regime. The Stribeck model is employed to represent the friction behavior in the gross-sliding regime, ensuring stationarity during friction regime switching. Based on the established friction model, a friction compensation method is developed in velocity control mode. The superior performance of this proposed friction compensation method is confirmed through sine-tracking experiments. Compared with the proportional integral controller and the Stribeck friction compensation method, the peak-to-peak value of the proposed method is reduced by up to 61.1 %, and the root-mean-square (rms) value is reduced by up to 81 %, with the smallest rms value reaching 0.13 mrad, significantly improving the dynamic tracking performance of the system. [ABSTRACT FROM AUTHOR]

In order to improve the state monitoring and adaptive control capability of inertial stabilization platforms (ISPs) with unknown loads, it is necessary to estimate the dynamic parameters comprehensively online. However, most current online estimation methods regard the system as a linear dual-inertia model which neglects the backlash and nonlinear friction torque. It reduces the accuracy of the model and leads to incomplete and low accuracy of the estimated parameters. The purpose of this research is to achieve a comprehensive and accurate online estimation of multiple parameters of ISPs and lay a foundation for state monitoring and adaptive control of ISPs. First, a dual-inertia model containing backlash and nonlinear friction torque of the motor and load is established. Then, the auto-regressive moving average (ARMA) model of the motor and load is established by the forward Euler method, which clearly expresses the online identification formula of the parameters. On this basis, the adaptive identification method based on the recursive extended least squares (RELS) algorithm is used to realize the online estimation of multiple parameters. The simulation and experimental results show that the proposed adaptive multi-parameter estimation method can realize the simultaneous online identification of the moment of inertia of the load, the damping coefficient of motor and load, the transmission stiffness, the Coulomb friction torque of motor and load, and the backlash, and the steady-state error is less than 10%. Compared with the traditional linear dual-inertia model, the similarity between the model based on the proposed adaptive parameter estimation algorithm and the actual system is increased by 65.3%. [ABSTRACT FROM AUTHOR]