Abstract:This paper proposed a measurement correction based multi-rate Kalman integrated method for the problem of spacecraft relative navigation using monocular vision and IMU. This algorithm divides the entire filtering process into two separate stages: measurement updating stage and time updating one. The sampling rate of the IMU as a fast one is generally chosen as the filtering period of the integrated naviga-tion system. Moreover, in each sampling period, the filter determinates whether to update the measure-ments of the vision system with slow sampling rate, andthe measurements are also used to modify the covariance matrix of measurement noise and state estimation error. Both theoretical analysis and mathematical simulations indicate that multi-rate Kalman filtering algorithm using measurement correction can increase the data output rate and improve filter performance as well as the redundancy of the relative navigation system.

Abstract:In order to improve the robust performance to parametric perturbations and external environment disturbances for rigid spacecrafts, an attitude tracking controller based on the discrete-time sliding mode control principle is proposed. The spacecraft model is firstly modeled. Considering the time-varying and interfering moments and even disturbances, the system is then decoupled into independent discrete-time subsystems via the input-output feedback linearization. To this end, the discrete-time sliding mode attitude control law is designed from the exponential approach law. Simulation results indicate that the discrete-time control system proposed can ensure the attitude stabilization of rigid spacecrafts while realizing the decoupling control among channels. Moreover, the system is robust to the parametric perturbations and external disturbances and the attitude angle tracking errors can be reduced effectively. In addition, the tracking dynamic characteristics and the sampling period are validated for the system considered.

Abstract:Many of Current DOA estimation algorithms have to be exerted on arrays whose inter-antenna distance are less than half wavelength of the arrivals to avoid the ambiguity phenomenon. However, to acquire decent performance in accuracy and resolution, arrays of larger aperture have to be adopted, increases the number of sensors, and enhances the complexity of hardware and cost. To which solve these problems, this paper proposes an algorithm oriented from Multiple Signal Classification (MUSIC), which operates on an array combined of multiple arrays of different apertures. The subarray of smaller aperture helps to eliminate the ambiguity, smooth the spatial spectrum and reduce the calculation complexity, while the larger subarray improves the performance in accuracy and resolution. The principle and steps of the algorithms are presented, and a detailed performance analysis and simulation results are given, which verify the validity of this algorithm.

Abstract:In LTE system, in order to improve system Packet Loss Rate (PLR) performance of scheduling algorithm for real-time traffics and solve the problem that the performance of Delay Prioritized Scheduler (DPS) algorithm will degrade in terms of higher PLR and lower system throughput with the increase of user number, we propose a DPS based scheduling algorithm which considers packet delay and instantaneous downlink channel condition of each user. System throughput can be improved by the utilization of channel conditions for different users, and user fairness can be guaranteed due to the information of different user delay. Simulation results show that the proposed algorithm can be used to achieve the tradeoff between system throughput and user fairness, and reduce PLR significantly under the Quality of Service (QoS) constraints of real-time traffics.

Abstract:In order to solve the problem that the BER and spectral efficiency restrict each other in the traditional modulation methods, we design a novel signal modulation and demodulation method where the cosine signal and the chirp signal are used as carriers to transmit cooperatively. In the modulation, each signal of the traditional QPSK modulation is inserted by a chirp signal to form the mix modulation. In this case, the new modulation will permit the four signals to transmit simultaneously; In the demodulation, consisting of the carrier signals, we design eight integrators. Moreover, the signals will be estimated by the maximum value of integral results. Numerical results imply that this modulation and demodulation method improves both BER and the bit pass rate.It means that the modulation and demodulation method we design in this paper obtains the comprehensive advantages between BER and spectral efficiency, and enhances the effective capacity of the system.

Abstract:In order to meet the demand of dynamic wireless network precised link connectivity modeling, considering wireless channel propagation characteristics and mobility models, the link connectivity model based on high order Markov chain is established. Parameters of the model are statistically analyzed. The model is employed to evaluate the link life time of wireless network. The relationship of link life time error and Markov chain order is compared. Analysis shows that the accuracy of link life time improves with the increasing order of Markov chain. In addition, the accuracy of link life time generated by Markov chain whose order is higher than 4 improves inconspicuously. Compared to the multi-state one-order Markov link connectivity model, the error of four-order Markov model link life time decreases 68%.

Abstract:With respect to the characteristics of product structure in large discrete manufacturing enterprise, a multiple level product structure which integrated self-made items, outsourcing parts, raw materials and making processes was proposed. Afterwards, aiming at the optimization and control for product design cost, a product and／or tree structure based on configuration model was established, in which the assembly feasibility satisfying the requirements of an item making process was represented by the definition of correlation between its components. Based on the single level product and／or tree structure, a design cost optimization model was then given. Simulation experiments were employed to demonstrate its effectiveness. The experiments showed that the proposed Opt-BOMP on model DFC can achieve a better cost product design than the DTC model. The Opt-BOMP has considered the quality requirements of a product, the impact of supplier on outsourcing materials, the technology requirements of a product and the combination of product design and manufacturing, it can improve the feasibility of a product design.

Abstract:In order to suppress the oscillation characteristics of relative navigation system caused by minimum measure resolution, an accurate microwave measure model is developed, and an adaptive step-size filtering algorithm is presented in the paper; Performance analysis and comparison between the adaptive step-size filtering algorithm and the low-bandwidth design algorithm widely used in the project is made. The theoretical comparison result indicates that the bias and random error increases inversely with the decreasing of filtering bandwidth, and convergence process becomes longer, but the adaptive step-size filtering algorithm largely reduces the performance loss. Simulation result shows that the relative velocity estimation error is 2E-3 m／s(3σ), which is reduced by one order of magnitude compared with the relative velocity estimation error of low bandwidth method, and can satisfy the mission requirements for high precision satellite formation.

Abstract:In order to investigate the influence of configuration of target on the ballistic performance, monolithic and three-layered targets were normally impacted by blunt-nosed projectiles in the velocity range of 190～450 m／s with the help of a gas gun, and also the photos of the impact process were obtained. Based on the tests, the residual velocity versus the initial velocity curves of the projectiles were constructed, and also ballistic limit velocities were obtained. The influence of combination configuration of target on the ballistic characteristic, including the ballistic resistance and failure models were investigated. Moreover, the penetration process of metal plates impacted by rod projectiles had been studied with numerical simulation code ABAQUS／EXPLICIT, and also the validation of models and parameters of materials had been proved by comparing the experiment results with numerical simulations. The results indicated that the ballistic limit velocity of multi-layered target was higher than that of monolithic target, and also there were differences between failure models of multi-layered targets and monolithic target. Moreover, the failure models of plates of multi-layered targets were in relation to their order.

Abstract:A stereo matching algorithm based on Census transform and improved dynamic programming is proposed to the problems of traditional dense stereo matching methods, which have high false matching rate in the textureless areas, depth discontinuities and occlusion. The initial local matching cost is calculated by sparse Census transform correlation, and the raw cost is also optimized by a dynamic programming method by involvoing bidirectional constraints of row and column simultaneously. Meanwhile, the confidence and texture of each pixel are measured for reference image. Finally, the disparities of non-confident or textureless pixels are estimated by fitting parameters of a plane model for the corresponding segment, and the dense disparity map was obtained as well. Experiment results demonstrate that the proposed algorithm achieves high matching accuracy and robustness, especially in the textureless areas, depth discontinuities, and occlusion as well.

Abstract:In view of the problem of limited usage scenarios as well as inaccuracy of state duration probability density function (SDPDF) in existing land mobile satellite (LMS) channel model, we propose a narrowband LMS channel model which is capable of describing much more operational scenarios accurately and effectively. The state sequence is achieved by using Semi-Markov chain which approximates the SDPDF as a lognormal distribution. Within each state the carrier-to-noise ratio (C／N) time series is generated and defined as a Loo distribution by combining with propagation parameters. Doppler frequency shift is applied in slow fading components to increase parameter database and extend usage scenarios. The state probabilities, the first-order statistical characterization of C／N time series, and the required margins of 90％ signal availability are investigated and compared with measurement results under different scenarios conditions. Simulation results show that the proposed model is effective for the representation of shadowing conditions on much more scenarios. In addition, it has a good applicability for different elevations and driving directions in different environments, and can be used in system performance analysis.

Abstract:Considering the narrowband two-state land mobile satellite channel model with variable model parameter at S-Band, an adaptive long-range prediction method is proposed based on weighting prediction. Firstly, a two-state Markov Gilbert-Elliot channel model with an ability of describing shadowing conditions of satellite communication downlink is established. And then, the future long-range channel state is predicted by weighting prediction, and the coefficients of linear auto-regression model are updated by iterative adaptive tracking method using the least mean square algorithm. Finally, the future channel fading series are predicted. Simulation results show that the proposed method not only can be used to predict the future long-range channel states and fading series accurately, but also improve prediction performance compared with the long-range prediction method. Moreover, this method has ability of real-time and low-complexity and can be used in the adaptive transmission performance analysis of narrowband LMS communication systems.

Abstract:The lattice reduction aided Tomlinson-Harashima precoding (LRA-THP) is computationally intensive. In order to reduce the computational complexity, a low-complexity group precoding algorithm is proposed for multi-beam satellite systems based on an existing group precoding algorithm. Users are split into groups according to the distance between beams in the proposed algorithm. Then, preprocessing matrix is obtained by maximizing the successive signal-to-leakage-plus-noise ratio (SSLNR) to suppress the inter-group interference. The LRA-THP is applied in each group. The characteristic of the multi-beam satellite channel is exploited to reduce the dimension of the preprocessing matrix which results in computational complexity reduction. Simulation results show that the complexity of the proposed algorithm is much less than that of the LRA-THP. Furthermore, the proposed algorithm reduces the complexity over the existing group precoding algorithm by 24％ while limiting the performance loss to 0.1 dB. In addition, the proposed algorithm can provide a flexible tradeoff between the performance and complexity.

Abstract:Aiming at the problems of the faults of NPP’s control rod drive mechanism, a fault information fusion method is proposed by using rough set neural network in making decisions based on the Internet of Things. The perception layer, network layer and supporting layer were constructed by involning the MEMS sensor, ZigBee module and Multi-Agent module, and also 6 kinds of input features were selected to represent scope of control rods displacement, reducing attributes as neural network Agent prior input module, module contracted rules as judgment criterion of hidden layers, concise rules of rough set Agent as judgment criteria of hidden layer, respectively. Simulation results verified the feasibility of IoT CRDM rod position monitoring system and the accuracy of rough set neural network fusion algorithm.

Abstract:As one of the most popular methods for direction-of-arrival (DOA) estimation, the root-MUSIC algorithm usually needs to find the roots of a polynomial by iteration with certain initiation in practical applications. In order to improve the computational efficiency and accuracy of polynomial rooting, it is of great importance to choose and to update appropriate initiations for root-MUSIC. To this end, a new technique for setting and updating the initiations of root-MUSIC is proposed in this paper, by making use of the characteristic of root-MUSIC as well as Least Average Distance to Unit Circle (LADTUC) rule. Theoretical analysis as well as simulation results demonstrates that fake roots are avoided and the speed of iteration is efficiently improved by the new approach, which hence provides new schemes for realizing root-MUSIC in practice.

Abstract:To effectively control the dispersion and avoid the aggregate of Fe₃O₄ nanoparticles in the water, the dispersion of Fe₃O₄ nanoparticles was investigated before and after ultrasonic bath in different concentration of NaCl solution. The experimental results showed that the dispersion of Fe₃O₄ nanoparticles was little of aggeregates in the 0.4 mol／L NaCl solution. Furthermore, the magnetic Fe₃O₄-10-Hydroxycamptothecin compounds were prepared by refining pH values of 10-Hydroxycamptothecin system, and then the Fe₃O₄-HCPT@SiO₂ core-shell structural nanoparticles were prepared, of which the diameter of the composite nanoparticle is about 120 nm. The drug release process proves the feasibility of this preparation method.

Abstract:To study the factors which can influce the thermal properties of both die and specimen, calculate the Interfacial Heat Transfer Coefficient(KIHTC) during hot stamping process is very important. A round table test and Beck′s inverse estimation method were used to study the relationship between the thermal properties and the KIHTC. The dies were made of materials with different thermal conductivity and heat capacity. The thermal properties in terms of martensite transformation were obtained by using specimen made of 22MnB5 sheet. Specimen made of stainless steel AISI-304 that does not have martensite transformation during quenching were tested as well for comparison. The results show that the KIHTC between boron steel specimen and die of ＃45 Steel is larger than that of H13 Steel (approximately twice as much) and the thermal conductivity plays a significant role; the martensite transformation yields a positive gain on KIHTC (approximately by 30.2％) and the change in thermal conductivity before and after phase transformation is a major contributor.

Abstract:Ultrasonic embossing is a new replication technique for polymer microstructures, and it is difficult to control the embossing process, and the process window is very narrow. Aiming at solving this kind of problem, energy control mode for ultrasonic embossing is proposed in this paper. PMMA was selected as the substrate, and embossing experiments based on energy control mode and time control mode were carried out. The results show that, in the energy control mode, under the condition of heat-assisted temperature 65 ℃, ultrasonic pressure 400 N, ultrasonic amplitude 11.4 μm and ultrasonic energy range from 700 J to 1 000 J, the depth replication rate was better than 92％. The temperature test experiments for heat affected zone show that, using the similar embossing parameters, the peak temperature in energy control mode is low and the temperature over the glass transition point is long. And this is the main reason for energy control mode has wider processing window which makes the process more controllable.

Abstract:For improving properties of 430 ferritic stainless steel coil, effect of chemical composition, equiax crystal ratio of cast slab,hot-rolling processing, annealing of hot coil on microstrutures and properties of steel were investigated and anlyzed. By adding bit aluminium, decreasing superheat of metal in tundish and strengthen eletromagnetic stirring simultaneously, the microstructure of cast slab could be improved. The experimental results show that the optimal heat treatment system could be identified under the contrast test in different heat treatment system; simultaneously, when the annealing temperature is 950～1 000 ℃,the finished steel plate could show be the excellent mechanics and process properties.

Abstract:In order to analyze the temperature rise of the heating module for sodium-sulfur battery, the theoretical model of the heating module and fitting model of the experimental temperature data were established on the basis of 3D transient heat conduction equation and Weibull function, respectively, and also the temperature rise process and the transient temperature distribution of heating module for sodium-sulfur battery were numerically simulated, and the effects of Weibull parameters on the temperature rise curve were further investigated. The results indicate that the Weibull fitting model could accurately describe the temperature rise process of heating module with high reliability, and the temperature rise rate inside the whole heating module presents nonlinearly decreasing trend with the increase of time, as well as the length from the module center. Furthermore, shape and scale parameter dominate the efficiency of the sectional temperature rise and the overall one respectively, and the technical reference is provided for the optimal design of heating module for sodium-sulfur battery and other heating devices.

Abstract:Aiming at the characteristics of imperfection and various of stealth target acquired by radar in complex electromagnetic circumstance, a new method based on improved grey correlation and distance optimization evaluation model was presented. Firstly, the shortcoming of common subjective grey correlation algorithm was overcome by the method. According to the subjective and objective, associated attributes of indicators, the weight of grey correlation algorithm was calculated in real time. Secondly, a set of indexes to evaluate the ability of radar based on performance and operational effectiveness was established. The anti-stealth radar evaluation distance and results were given combined with the stability and effectiveness of the sample. The analysis of theory and results of simulation proved that, in contrast to the common subjective grey correlation algorithm, the composite weights grey correlation algorithm had higher ability of assessment and stronger computation reliability.

Abstract:To study the mechanical properties of improved composite L-shaped concrete-filled steel tubular columns, 18 axial compression tests of improved composite L-shaped concrete-filled steel tubular columns are carried out. The influences of all parameters included steel tube thickness, concrete strength and slenderness ratio on the mechanical properties of the specimens are analyzed, and the expression of bearing capacity is proposed. The test results indicate that the waist drum failure mode, local buckling (or cracking) failure mode and flexural failure mode are occurred in tests; the steel tube thickness, concrete strength and slenderness ratio are the key factors influencing the bearing capacity, but the increase of steel tube thickness is more beneficial to the improvement of the bearing capacity, if the steel ratio is larger, the confined effect of steel tube to core concrete is stronger. The bearing capacity calculation results are in good agreement with the experimental results.