Abstract:In order to explore the mechanism of dielectric barrier discharge at high angle of attack on the highlift wing, the simulation of the aerodynamic characteristics of the highlift wing with the coupling of the body force model and the Eddy Viscosity Transport Equation turbulence model is carried out. The simulation model is validated by comparing the experimental data with the simulation model at the flow velocity of 45 m/s. The model is used to analyze the streamlines of the chordwise and spanwise sections of the wing. The results show that the DBD at the leading edge of the wing can obviously improve the aerodynamic characteristics of highlift wing at high angle of attack, improve the vortex structure of the upper airfoil and control the separated flow. The maximum lift coefficient of the wing increases by 111％ and the stall angle of attack is delayed 2°. And also, with the angle of attack increasing, the effect of flow control is gradually weakened until disappearing.

Abstract:This paper presents a Backstepping-L1 adaptive control method aimed at the problems that there are outside interferences such as crosswind, etc., and nonmodeling dynamic uncertainties exist in aircraft itself in the process of flight for attitude control of multirotors. Firstly, according to the kinematics and dynamics equations of multirotors, the paper designs a Backstepping control law by a Lyapunov function under no consideration of uncertainties to realize a fast, accurate and stable control target. Then, under consideration of the influence of uncertainties, the paper introduces adaptive law and state predictor into the system on the basis of Backstepping controller. With the augmentations of adaptive law and state predictor, the real time estimation of uncertainties and online state prediction are realized. A L1 adaptive controller is designed to compensate the influence of uncertainties and make the system robustness and fault tolerant. And its stability analysis is realized by introducing a stable reference system. The analysis result shows that the state predictor, adaptive law and control law can ensure the system stable. MATLAB simulator is provided to demonstrate the performance of the presented control scheme.

Abstract:Typical mission profiles of aeroengine not only represent flight mission characteristics, but also weigh up life damage resulting from flight missions. Low cycle fatigue damage, steady creep damage and thermal shock damage are regarded as the dominate elements of mission profile induction. In view of a certain type of aeroengine 77 statistical parameters of 13 flight parameters are composed of original load matrix, and then 71 flight profiles are clustered and induced on the system clustering method, principal component clustering method and fuzzy clustering method. The results show that the original load matrix reflects aeroengine usage employ and that parameters of profile induction have strong independence from each other. In comparison with other methods, the mission profile collections on the system clustering method enable to reflect corporate characteristics and attributes.

Abstract:Crossing waypoints location problem (CWLP) is a core of air route network planning. Based on the situation, a model of multi-objective optimization for CWLP is built, judged by the two factors of total airline cost and total flight conflict coefficient and proceed from the economic and safe aspects of air route network. During the solution, multi-objective bat algorithm based on dynamic gradient weight coefficient is adopted to make sure that the cost and flight conflict coefficient can obtain optimal solutions at the same time. In the end, this paper takes Beijing flight information area as a simulation and gains four kinds of non-dominated solution by comparing BA with other algorithms. The result indicates that the BA in solving the problem can get a more optimal solution. Meanwhile, in consideration of two groups of weight according to the preference of economy or the safety, the data show that the proportional reductions of the network operation cost and conflict coefficient in these two situations respectively are 9.99%, 15.64% and -3.97%, and 65.81%, compared with the initial network. The conclusion of the simulation is that the method can provide various solutions for the decision makers in the design for crossing waypoints location.

Abstract:It is one of the hot issues for international air traffic control research to utilize advantages of crosswind conditions for reducing the wake separation and enhancing airspace capacity appropriately In this paper, the wake vortex flow field of A320 airfoil is established. Based on the RANS method, the RKE equation is used to close the Reynolds stress term by two equations UDF (User defined function) programming technique is applied in establishing aircraft wake vortex flow field under the crosswind field of static wind, 1 m/s, 4 m/s, 7 m/s respectively. Through the TH1A supercomputer numerical simulation of wake vortex is therefore implemented. Hence, the evolution trend of the parameters such as the vortex core vertical sinking, the vorticity attenuation, the horizontal motion of the vortex core and the vortex core velocity are analyzed The results show that under the condition of static wind, with the slow sinking of the vortex, vortex vorticity decreases gradually. Under the disturbance of crosswind, the vorticity of vortex and the rolling moment increases rapidly in a short time Meanwhile, wake vortex spacing decreases rapidly after separation and rebound quickly. In the vertical direction, the vortex repeatedly jumps up and down. What’s more, the formation of strong crosswind induced turbulence shear gradient will lead to the vortex shedding, vortex bursting and rapid dissipation In the horizontal direction, the vortex will be blown away from the main flight path quickly under the impact of strong crosswind which is of great benefit to reduce the required wake separation and improve the efficiency of airport operation

Abstract:The accurate geomagnetic field value is a prerequisite and foundation for the geomagnetic navigation. To solve this problem caused by magnetometer in actual magnetic field measurement influenced by environmental magnetic field, the influence of hard iron and soft iron errors on magnetic measurement is analyzed and the parameterized geomagnetic measurement compensation model is constructed firstly. The geomagnetic field is simulated by using three pairs of Helmholtz coils to generate uniform magnetic field with the software of ANSYS. By setting the different parameters of interference source and rotating the magnetometers in 360 degrees in the simulation model, the three dimensional magnetic field values with and without interference are got. Those parameters of the model are estimated using least squares based algorithm and geomagnetic measurement errors are calibrated. The simulation results show that this compensation method is simple, and easy to use, and has higher error compensation ability, and geomagnetic measurement errors can be reduced from 20000nT to several nanoteslas.

Abstract:Currently, relay approach is a feasible scheme in solving the communication blackout problem when spacecraft reentries. This paper builds up a model of plasma sheath at leeward, analyzes influence of reentry spacecraft pitch angle on signal transmission in sheath, and contrasts the transmission of Ka-band signals with S-band signals in the leeward plasma sheath under initial pitch angle of the spacecraft reentry atmosphere. The result shows that the attenuation of signal electromagnetic wave in plasma sheath decreases with increase of pitch angle; under condition of the same pitch angle, the transmission of Ka-band signal is significantly superior to the transmission of S-band signal. Compared to S-band signal, Ka-band signal's the transmissivity on leeward increases by at least 55%, with decrease on the attenuation by at least 33.69 dB. It's suggested that Ka-band signal can be chosen as the communication frequency between reentry spacecraft and relay satellite. Relay approach is Proposed by relay optimum proposal, providing ideas to solve the reentry spacecraft communication blackout problems.

Abstract:Targets’ micromotion feature is one of the effective features used for recognition at the middle section of the ballistic curve. Aimed at the problem that a single radar is rather limited in extracting micromotion information, this paper proposes a novel algorithm based on the narrowband radar network to extract precession features. First, a coneshaped target model and a narrowband signal model are established. Then, each scattering point in different perspective is matched by frequency analysis based on transforming nonideal scattering point into ideal scattering point. Finally, by using the microDoppler of conic node to compensate the bottom microDoppler of cone, compensation coefficient is solved when the radar aspect variance is minimal. Furthermore, parameters are obtained by combining the microDoppler of two radars. The simulation results show that the algorithm can extract micromotion parameters and structured parameters accuracy.

Abstract:Aimed at the problem that the existing literature to analysis influence of structure parameters on the interior ballistic performance is based on the single variable method on no consideration of the coupling relationship between the structure parameters, an integrated simulation model from the opposite design of internal ballistic equation to the positive calculation of interior ballistic equations is established, the coupling relationship between the structure parameters is considered, the modification method of interior ballistic design equation is put forward, and the variation law of interior ballistic performance based on the two dimensions of space dimension and time is analyzed. The simulation results indicate that design equations are derived in simplification causing the truncation errors and magnifying ideal throat area, and with the increase of low pressure chamber diameter the amplification becomes obviously. In designing a particular cylinder velocity and working pressure of high pressure chamber, the smaller the initial diameter and the height of the lower pressure chamber is, and the smaller the throat area is, and the greater the impact load of the missile is, and the shorter the movement time of the missile is. Choosing a reasonable size of the lowpressure chamber can make the maximum pressure of the low pressure chamber and the maximum acceleration missile arbitrarily adjustable.

Abstract:Wideband radars have particular advantages in aspects of antijamming, object identification and tracking. In this paper, the characteristics of wideband radar sea clutter are analyzed based on the rough surface scattering model. Firstly, the twodimensional ocean rough surface is built by using PM spectral function, and the tapered incident wave is applied to eliminate the edge diffraction. Afterwards, the wideband radar clutter amplitude of scattering cell can be obtained by using the physical optics (PO) scattering model and subband synthesis. Finally, the wideband radar clutter echoes are modeled and simulated. The spectrum characteristic and high resolution range profile (HRRP) of the sea clutter are achieved. The impacts of bandwidth, grazing angle and wind speed on the characteristics of sea clutter are analyzed respectively. The simulation results show that radar band width increase and the grazing angle decrease while the echoes amptitude of sea clutter have a significant decline. Meancohile the inpact of wind speed is not obvious.

Abstract:The N-doped carbon-coated LiFePO4 composite is prepared by the sol-gel method taking C2H4N4 as the nitrogen source. Meanwhile, the effect of nitrogen contents on the structure and property of LiFePO4@C is investigated. The obtained results show that the citric acid and C2H4N4 decompose insitu forming a N-doped carbon layer covering the surface of LiFePO4 particles during the sintering process, effectively enhance the electronic contact between the LiFePO4 particles, and improve the electrochemical performance of LiFePO4 electrode material. When the nitrogen content in LiFePO4@NC is 0.35 wt％, the corresponding electrode exhibits the best electrochemical performance. The initial discharge capacity of LiFePO4@N 0.35％C reaches 157.2 mAh/g at 0.1 C between 2.5 V and 4.2 V, and this capacity almost remains unchanged after 30 cycles.

Abstract:Aimed at the problem that the localization accuracy of current indoor WiFi positioning method is low a new method of WiFi indoor carrier phase precise location based on Chinese remainder theorem is proposed. According to the characteristics of WiFi signal multifrequency modulation, the proposed algorithm explores the potential auxiliary efficiency of WiFi technology to improve the indoor ranging performance without changing the structure of commercial hardware. The congruence group is constructed by using the carrier phase measurement of multiple frequency points, and solving the group to measure distance based on Chinese Remainder Theorem, thus effectively eliminating the integer ambiguity in the carrier phase ranging. On the basis of analyzing the ranging accuracy and the noise sensitivity, a method is presented reduce noise sensitivity. According to the actual positioning application requirements, the carrier frequency, SNR, and measurement distance are respectively configured to build a simulation system. This method is compared with the existing RSSI and TOA for 100 simulation experiments. The simulation results show that the average ranging accuracy of the proposed method is 88 mm under the condition of 20 dB SNR and 25 m measurement distance. The method is superior to the existing universal WiFi positioning method and is of great value to application in terms of theory and practice.

Abstract:Based on the complementarity of these two features, this paper presents an infrared target tracking algorithm in combination with the deep feature and the gradient feature. The deep feature and gradient feature are used to represent the semantic information and the local structure information in this paper, enhancing the ability to characterize any target. Next, the tracking models based on different features can further improve the tracking performance. Finally, the paper builds up a model mutual mechanism based on the combination of deep feature tracking model and gradient feature tracking model, implementing positioning precisely to the target. The article selects the latest infrared tracking database and uses the database to verify the effectiveness of the algorithm. The results show that the algorithm in this paper achieves a 3.8％ improvement in accuracy and obtains a 4.3％ improvement in success rate, enabling to effectively handle the effects of the background similarly and deformation.

Abstract:Design of gate tracking is usually made based on residual estimation, but the traditional residual estimation method is comparatively poor in precision under condition of the unknown target state. For this problem, this paper analyzes the application environments of two kinds of the existing residual estimation methods, and proposes an interactive estimation algorithm based on Markov chain. Firstly, the existing two kinds of estimation methods are used to predict respectively the residual value of next time. The prediction error is defined and calculated according to the predicted values. Then, the likelihood value is used to calculate the weight of each methods based on the transition matrix of Markov chain. Finally, the residual value of next time is sought out through weight summation. The simulation experiments show that the prediction accuracy obtained by this method is higher than that by the traditional methods under condition of the unknown target state.

Abstract:In view of the performance decline caused by spectrum mismatch in transform domain communication system, a basic function generation algorithm based on joint channel status coding is proposed in this paper. The algorithm is used to conduct quarternary synthetic coding on the channel status of both transmitter and receiver, divide the joint channel into four states, choose good frequency points for data transmission according to the mismatch rate, and then implement filtering on the received signal before demodulation. Theoretical analysis implies that, in the same situation, the spectrum utilization rate of the joint channel status coding is higher than that of spectrum exchange mechanism, thus avoiding the transmitter and receiver to give up communication further close to the real situation. The simulation results show that the antiinterference performance of the algorithm is superior to that of spectrum exchange mechanism, and can effectively improve the spectrum utilization of the system, and reduce the impact of spectrum mismatch on interference performance, and expand the scope of application of TDCS.

Abstract:The great kinetic energy of penetration can cause damage to the structure. It is important to the protection engineering that predicting the penetration damage effect of the underground caverns accurately. In order to solve the problems of current method, an improved IGWOLSSVM model is put forward. This model can form a mapping relationship between inputs and outputs by training the training samples. It can get corresponding peak pressure of the vault according to the inputs, and predict damage effect of the underground caverns with different spans and different burial depths. The results of ANSYS/LSDYNA numerical simulation show that the model has good prediction effect on penetration effect of the underground caverns, which can meet the engineering requirements.

Abstract:The vehicle routing problem with simultaneous pickup-delivery and soft time windows (VRPSPDSTW) is typical of NP-hard combination problem. Aimed at the problems that convergence speed is slow and easy to fall into local optimum value at the later stage for standard cuckoo search algorithm (CS), this paper puts an improved strategy based on the mixture of saving algorithm and stochastic probability in initialization, and adopts the dynamic discovery probability and variation mechanism of pheromone orientation. The performance of the modified cuckoo search algorithm (MCS) is proved by quantitative test. And then the modified algorithm is applied to solve the vehicle routing problem with simultaneous pickupdelivery and soft time windows, compared with the existing algorithm, and the superiority of the modified cuckoo algorithm in practical engineering is verified.