Abstract:Using the object-oriented design method, a general, flexible and reliable aircraft engine performance simulation framework is designed. The simulation platform is divided into three layers clearly and the corresponding kind of model is established under each layer, thus the data exchanges among layers are flexible and effective. The fundament component class library is established and can be used to build different aero-engine simulation models. The performance simulation framework is applied to several calculating missions including steady, transient and real-time simulations. Based on the simulation framework, a two-spool mixed flow turbofan simulation model is build and its steady and transient progress are calculated. The calculation results are of high precision and verify the effectiveness of the framework.

Abstract:The sand thickness degree namely fineness modulus Mx of fine aggregate has some effect on various performance of concrete. The initial fine aggregate is sieved into four different kinds of sand as 2.11、2.64、3.15、3.6. By keeping the basic mix proportion unchanged, four kinds of pavement concrete are made up with these four kinds of sand，and through a lot of experiments, the workability, compressive strength, flexural strength, frost resistance，impermeability and wearing resistance of these four kinds of pavement concrete are systematically studied, the influence rules of sand fineness modules on the performance of pavement concrete are found, the fineness modules range of the sand suitable for airport pavement concrete is defined. The results show that the optimal range of fineness modules of fine aggregate is synthetically considered and determined as 2.64 or so. If the fineness modulus is over this basic range, the strength, frost resistance and impermeability will decrease rapidly, if less than that range, the wearing resistance will decrease rapidly.

Abstract:In order to improve the accuracy of fault feature extraction, the stochastic resonance (SR) method is proposed in the pretreatment of vibration signals, then the fault feature is extracted based on the method. First, the de-noising principle of SR is presented, and the mutable scale SR, which is suitable for large parameter signal， is analyzed. Then a fast optimization method of frequency compression ratio R is put forward. The vibration fault feature sets based on time domain, frequency domain, time-frequency domain are extracted respectively to test the proposed feature extraction method. Finally, the discrete degree index based on between-class and within-class is applied to analyze the classification performance of feature set. The analysis result shows that the classification indexes of the feature sets extracted from SR output signal are obviously superior to those from the original signal, the feature extraction accuracy is improved notably.

Abstract:Exact prediction of unsteady aerodynamics is of great importance to the design and study of advanced combat aircraft. In response to the problem of complex calculating and lack of considerable factors in handling normal state-space model, a new flow separation model and a new state-space aerodynamics model are put forward in this paper. Compared with normal state-space model, complex calculation of differential equations is avoided and simultaneously a new influence factor -pitching angular velocity is introduced in the new state-space model which makes the physical meaning of the new state-space model proposed in the paper become clearer and more definite. At the same time, the static and dynamic proceedings are combined into one equation by the flow separation model proposed in the paper. At last, the large amplitude oscillation wind tunnel data are used for testing, the result suggests that the unsteady aerodynamic model proposed in this paper can describe the time-delay characteristics of the aerodynamic force and fit well with the wind tunnel test data.

Abstract:According to RTA operating map, a highly loaded single stage fan on low corrected speed and at various stator setting angles are simulated using threedimensional (3D) numerical simulation software NUMECA. The results show that under the condition of low conversion rotating speed in the highaltitude and at a highspeed, a partial fan passage is chocked up with flow and the increasing of the mass flow of fan is restricted due to the increasing negative angle of attack of blade loads. The negative angle of attack of blade is sensitive to stator setting angle. The adjustment of stator setting angle can partly restrict the negative angle of attack of blade and nearly remove the chock of fan passage, which loads the increasing of the mass flow and adapts the demand of the fan during wind milling.

Abstract:A method to design planar and low insertion loss phase shifter with broadband characteristic of 90o difference is presented by utilizing the nonlinear phase characteristic of the simplified composite right-/left-handed transmission line. The measured results show that the proposed phase shifter achieves 2.9~8.4 GHz (97.3%) bandwidth with return loss ≤-10 dB, insertion loss ≤0.7 dB and phase instability ≤±5°. Whereas, the relative bandwidth of the conventional difference phase shifter is only 11% when it simultaneously satisfying the above indexes. The proposed structure is simple in design and is easy to be fabricated.

Abstract:A mission assignment model of multi-anti-missile combat based on the effectiveness optimization is proposed. First, the relation between mission assignment and target allocation is clarified, based on which the mission generation principle is put forward and the mission assignment model considering the uniformity and coherence performance is established. Then, in order to describe the cooperation of schemes, the basic effectiveness, the self-cooperative efficiency and the inter-cooperative efficiency are defined. At last, the particle swarm optimization (PSO) is used to solve this optimization problem and the simulation shows that the method and the model proposed in this paper are effective in mission assignment problem for cooperative anti-missile combat, and also shows the advantage of mission cooperation in the cooperative anti-missile mission of multi-anti-missile weapon systems.

Abstract:Radar radio frequency (RF) stealth of fighter plane is the important side of stealth fight at fight plane tracking model. First, the RF stealth concept is introduced. Secondly, an optimization control model restricted by tracking precision and accumulation intercept probability is constructed for single target tracking problem. Thirdly, the control strategy of the radar adaptive emission interval and emission power is put forward through solving the model. Finally, by comparison with two other control models FRIAF，FRIFE by computer simulating, the RF stealth ability of the fighter plane is improved .

Abstract:According to the condition that the operating performance of the traditional GNSS receiver is not ideal in the weak signal environment，firstly the article analyzes the working principle of traditional receiver and vector receiver, summarizes the traditional receiver's performance deficiency in the weak signal environment，secondly the tracking performance of the traditional scalar receiver and that of the vector receiver are compared in the weak signal environment, and simultaneously the method of setting up the delay interval of double-code is put forward to optimize the vector tracking performance. The technology of vector tracking is used to make up for the defect of traditional receiver in the weak signal. The experimental results show that the double-code delay interval vector receiver which uses EKF algorithm is superior to the traditional scalar receiver in tracking performance in the condition that the carrier-to-noise ratio is 15-22 dB/Hz, and its' tracking error is about 20 ns smaller than the tracking error of the one-code delay interval vector receiver.

Abstract:Using current statistical model for maneuvering target tracking has a good effect. However, maneuvering frequency and ultimate acceleration are defaulted by human's experience. When the given parameters are not accordant with actual situation, the capacity of tracking maneuvering target will decline. In view of the problem that the tracking performance of model is dependent on the prior parameters, this paper puts forward an adaptive tracking algorithm based on truncation gauss probability model for target tracking. In this model, the maneuvering situation of targets is characterized by the distance function, the status yawp and filtering gain of model is adaptively adjusted by using the exponential adjustment function to modulate maneuvering frequency and ultimate acceleration, which can improve the matching degree between maneuvering target model and the actual movement of the target. According to the simulation results, the capacity of tracking maneuvering target is improved, comparing TGPNMKF with ACS and TGPMKF.

Abstract:The model of radar sea clutter using fractal theory has a wide application in many research fields. This paper proposes inserting a time-varying random sequence in Fractional Brownian Motion ( FBM ) model for obtaining an approximate multi-fractal stochastic process to simulate the sea-clutter sequence based on the analysis of multi-fractal characteristic and FBM model. Through Matlab simulation and the comparison with the measured data，the result shows that the sequence produced by the model proposed in this paper is multi-fractal，which can effectively simulate the sea clutter.

Abstract:This paper introduces a new kind of equivalent circuit of single-feed circular polarization micro-strip patch antenna (CPMA) based on Cavity Model Theory and gives the calculating formula of axis ratio. Meanwhile, a novel circular polarization micro-strip antenna is designed. The axis ratio calculated based on equivalent circuit agrees with the simulated and measured results. The above provides a new method for debugging the axis ratio of circular polarization micro-strip patch antenna.

Abstract:The packet sampling algorithm based on mask matching is a practical distributed traffic sampling algorithm. But the algorithm is ineffective in measuring an important network traffic characteristic, which is the distribution of packet arrival time interval. First of all, the reason leading to the problem is analyzed according to the error theory. Then, an improved program of double sampling is introduced in the initial algorithm in order to reduce the system error of measurement. As the improved algorithm will bring extra burden to the measurement system, a solution which is to increase the sampling mask bits is put forward and its feasibility is demonstrated. Finally, the improved algorithm is tested with the actual network traffic data. The experiment results show that the measurement of the distribution of packet arrival time interval is in line with the real situation. And it has little effect on the measurement accuracy of other network performances.

Abstract:To solve the problem of the sparse-aperture ISAR imaging for the target with rotating parts is poorer, a method based on sub-aperture Chirplet transform and Compressed Sensing(CS) is proposed in this paper. Firstly, the sparse ISAR imaging model of the target with rotating parts is established, then the effect of micro-Doppler of the target with rotating parts in broadband radar is deduced, and then the influence of the sparse of aperture and the micro-Doppler together is analyzed. Secondly, the radar echoes are decomposed into a series of Chirplet basis, getting rid of the micro-Doppler signal in sub-aperture based on the difference of the Chirplet parameters of the echo signals of main parts and rotating parts. Finally, to recover the imaging from the subaperture based on the CS method of Orthogonal Matching Pursuit (OMP) algorithm, getting the high quality imaging results of the target with rotating parts. Simulations show the method could eliminate the micro-doppler effect and achieve high quality imaging.

Abstract:Micro-motion is one of the most significant characteristics that can distinguish warhead from decoys. A simulation software is built based on VC++6.0 in the paper, which can be used to analyze the warhead's micro-Doppler feature and display three-dimensional, visual view of warhead with micro-motion. The software can acquire micro-motion information from warhead echoes by means of STFT,in the meanwhile, the 3D visual view is obtained by DirectX technique. The software can provide both theoretical and practical micro-Doppler feature curves of warhead which vary from different radar carrier frequencies, spinning frequencies, conning frequencies, precession angle, et al. The software works smoothly and responds quickly. The theoretical micro-Doppler curves are consistent with micro-Doppler curves of the echoes by time-frequency analysis method, and the 3D view scenes coincide with the micro-motion greatly in display.

Abstract:In GPS repeater deception jamming, time-delay is a key technique, when time-delay is illogical, receiver's clock off-sets will be changed, deception jamming can be identified easily and the success rate of the deception jamming will be reduced. The theory of GPS Pseudo-range is used in this paper to derive the time-delay algorithm and analyze the effect of different calculation results on receiver's clock off-sets. The conclusion is obtained as that when the distance between transmitted satellite and jammer plus the distance between jammer and the real locus is no more than the distance between transmitted satellite and fictitious locus, jamming has no effect on receiver's clock off-sets, otherwise it has an effect on receiver's clock off-sets. From this point of view, the deployment location of jammer is analyzed: while the jammer is situated on the line formed by satellite and real locus, the selection scope of fictitious locus with no effect on receiver's clock off-sets is the largest.

Abstract:A new TDCS adaptive threshold selection algorithm based on Otsu guidelines is proposed. In this algorithm, the spectral amplitude of the channel sensing are gray mapped, the spectrum grayscale is divided into background noise and interference by using Otsu guidelines, the best classification threshold is determined as the TDCS interference-rejecting decision threshold as well. The method is of strong adaptive capacity based on the perception of the channel and can be used to search the best decision threshold dynamically. Simulation results show that, the proposed method demonstrates superior performance than the traditional methods in the changing of channel background noise, especially when the background noise is increased to a certain extent, the communication system with traditional fixed threshold method will not work properly, but the use of the proposed method still makes the system performance good.

Abstract:Aimed at the poor performance of the wideband spectrum detection under low SNR, a novel cooperative wideband spectrum detection algorithm is presented based on compressed sensing for cognitive radio. By using the algorithm，first the measurements of cyclic spectrum from the signals` cross-correlation function of compressive samples are achieved on the basis of the unique sparse property of wireless communication signals in cyclic spectra region. Then all signals' cyclic spectra are reconstructed in the entire wideband by adopting the Sparse Adaptive Simultaneous Matching Pursuit (SASMP) cooperative algorithm. Simulation results show that the algorithm proposed has a better performance under Raleigh fading channel and low SNR environment, and the SASMP cooperative algorithm is improved in reconstructing quality and algorithm complexity compared with other classical algorithms.

Abstract:In view of the present disordered situation of using physics quantity and formula for infrared contrast calculation, the paper presents that the criterion of physics quantity used to evaluate the contrast should be infrared irradiance at the detector surface by analyzing the purpose and the actualized measures of infrared detection. When the object and background are in different positions, and both of them are far away from the detector, it is improper to calculate contrast by radiance or radiant emission. In order to make the contrast of infrared target and background represent effectively the infrared feature differences of the target-background, the infrared radiation relative contrast is defined by the ratio of the absolute value of the target and background difference in infrared irradiance at the detector surface to their mean value.

Abstract:H2-MAC, which was proposed by Kan Yasuda in Information Security Conference (ISC) 2009, is a new type of MAC construction. Compared with HMAC,H2-MAC is much easier for algorithm implementation and key management, for it gets access to the key only once. This paper first presents an equivalent key recovery attack H2-MAC-SHA-1 reduced to 53 (20-72) steps, which conduces to a universal forgery attack directly. Firstly, an H2-MAC-SHA-1 distinguisher is constructed. Then, the intermediate chaining variable, i.e., the equivalent key is recovered by using the distinguisher and bit flipping technology. Consequently, the universal forgery attack is processed. The adversary unknowing the secret key can process the universal forgery attack by computing the valid MAC value of M, which can be an arbitrary message. The complexity of the attack is about 299 queries, which is much lower than the ideal complexity of the universal forgery.

Abstract:For any positive integer , the Smarandache double factorial is defined as the smallest integer such that , where m!!=1·3·5…m, 2n2·4·6…m, 2n . The paper conducts the study of the mean value of the Smarandache Double Factorial function by the elementary and analytic methods, obtains a sharper asymptotic formula for the Smarandache Double Factorial function , and thus solves the problem proposed by Felice Russo in reference \[4\] .

Abstract:In order to improve the quality of three-phase inverter voltage output waveform and decrease the harmonic component and aberration rate of the output voltage, this paper presents a control scheme combined with fuzzy control, neuron study and PID control. With DSP as the control core, voltage output waveform is transformed by Clarke and Park vector transformation. Neuron PID controller is used to adjust PID controller parameters online, and the fuzzy controller is used in Neuron PID controller to form the compound control strategy. And based on 60 degrees rotating frame, SVPWM technology is used in three-phase inverter control system. The control system is simulated in the situations of steady-state load, dynamic load and asymmetric load. The simulation results verify that the use of the scheme can obtain high quality voltage output waveform with low harmonic component and aberration rate.