Abstract:Aimed at the problem existed for extending service life of aircraft structure at present, a method of fatigue /durability safe life extension of aircraft structure is put forward, i.e. the equivalent service life extension method. The basic principle of equivalent service life extension method can be illuminated as: the test data and service data of the same type of fleet aircraft are transferred into the equivalent using data under the same loading spectrum, the equivalent using data are fused and comprehensively analyzed based on reliability theory, then the fatigue /durability safe life of fleet aircraft are assessed and extended (namely the service restriction of fatigue safe life is relaxed). The basic process of equivalent service life extension method is described further on the basis. According to the basic principle and process of equivalent service life extension method, the fatigue /durability safe life of fleet aircraft structures can be determined and extended, the service restriction of the same type of serve fleet aircraft is relaxed gradually. The equivalent service life extension method can be used to provide the theoretical basis for the service life extension of the same type of service fleet aircraft.

Abstract:In order to overcome the defect that the impact velocity is assumed between blades and foreign object in present method, and to deeply search the law for an aeroengine blade impacted by the foreign object from the runway, the impact velocity of foreign object against the aeroengine blade is estimated in the paper. Firstly, taking the tested results as a basis，velocity induced by the air vortex from the runway surface to the inlet port is studied. Then, velocity equation from the inlet port to the blade is deduced by using the momentum theorem. Taking a blade as a reference，expressions of both the impact velocity and the impact direction relative to the blade are found. At last, a certain type of the airplane and its aeroengine are taken as example, the change rule of the motion velocity in inlet channel is studied. The results show that the foreign object motion velocity relates not only with the foreign object shape, dimension and material，but also with the aeroengine working state, the height and the length of the inlet port. The impact direction is out of vertical to the blade surface.

Abstract:Aimed at the problems that the unknown statistical feature of measurement noise affects the filtering precision of integrated navigation, an interacting multiple model algorithm based on improved innovation adaptive filter is proposed. In the process of estimating the innovation covariance, a set of estimation windows with different lengths is used to optimize the selection of the estimation window. Then the measurement noise covariance is estimated, taking this estimated value as a centre, the models of interacting multiple model algorithm are built symmetrically, and the subfilters in the algorithm is fed. The contradiction between the number of model and the computing speed is solved by using this algorithm. The simulation results show that this method is high in accuracy and strong in antiinterference ability, compared with the standard Kalman filter algorithm and the traditional innovationbased adaptive multiple model method.

Abstract:Aimed at the problem that high access roundtrip delay and low throughput exist in traditional physicallayer network coding collision retransmission scheme in satellite slotted ALOHA system, an improved random network coding based collision retransmission scheme in satellite slottedALOHA systems is presented. This strategy brings in random network coding based on the physical layer network coding, through the source node data packet random coding, the receiving node utilizes Gaussian elimination method to obtain the original packet. A mathematical model of the proposed strategy is established, and the date packet format for the strategy is designed, and then the throughput and transmit delay are derived in theory. The results indicate that the strategy is effectual in resolving the collision, greatly reduces the transmission slots, and the strategy has a high throughput when the number of users is a few.  [WTHZ]Key words:[WT]satellite communications; slotted ALOHA; physical layer network coding;random network coding;throughput

Abstract:The turbine blade is one of the crucial components in advanced aeroengines. It is of importance to apply the thermal barrier coating (TBC) to the turbine blade in a bid to enhance its high temperature resistance and corrosion resistance performance. However, defects involving wallthinning and delamination considerably decrease the protective effect of inservice TBC, which significantly influence the safety of turbine blades and aeroengines. This paper intensively investigates the technique for quantitative NDE of TBC which is subject to wallthinning defects in micrometers. It has been found that highfrequency eddy current technique in conjunction with the inverse model is applicable and effective for NDE of TBC. The establishment of eddy current impedance signal  the thickness of TC and the thickness of BC the analytical equations and combining with the inverse algorithm and the pickup coil impedance signal, the simultaneous solving the thickness of TC and BC. And then add them up, getting the thickness of TBC. To validate the computational results, by scanning electron microscope (SEM) to measure the true thickness of sample thermal barrier coatings. The results show that this method can achieve efficient quantitative assessment of thermal barrier coating of turbine blades with accuracy over 90%.

Abstract:In order to cope with the problem of low efficiency of GPS spoofingsignal injection, a GPS spoofing pattern based on denial environment which covers for signal injection is proposed. With an analysis on exchange of signal carrier noise ratio, the acquisition and tracking of spoofing signal in this pattern is discussed. Given representative parameters of GPS signal and receiver, the preferential signal ratio of spoofing signal to authentic signal and power of bandlimited white noise are calculated for the requirement of constructing denial environment. This jamming pattern is proved from the perspective of acquisition and tracking of spoofing signal, at last the general limit of signal ratio of spoofing signal to authentic signal and power of bandlimited white noise are deduced.

Abstract:This paper analyzes the pseudorange relationship between different frequency signals, and proposes a multifrequency receiver autonomous integrity monitoring (RAIM) algorithm. Aimed at the problems that measurement error covariance matrix is not diagonal, the paper proposes a new prewhitening method which can easily be implemented in a receiver. In addition, the paper analyzes the RAIM algorithms from different frequency points. The simulation results show that the multiplefrequency algorithm can eliminate the ionosphere error so that the positioning error can be reduced to less than 10 m. In addition, when the pseudorange deviation is less than 50 m, multifrequency RAIM algorithm can still be applied in detecting and identifying fault satellite. And the triplefrequency RAIM algorithm is in an advantageous position compared to dual algorithm, which would have a tempting theoretical and practical value for the future research of multifrequency receiver autonomous integrity algorithm research.

Abstract:In this paper, a polarizationreconfigurable antenna with metalsurface is proposed. The antenna consists of a metalsurface placed atop of a microstrip slot antenna and in direct contact with a microstrip slot antenna. By rotating operation to change the relative position of the metalsurface and slot antenna, the antenna can be reconfigured to realize linear polarization, right hand circular polarization (RHCP) and left hand circular polarization (LHCP). The results show that the impedance bandwidth can reach 32% and 10% in circular polarizations and linear polarization respectively；in right hand circular polarization and left hand circular polarization 3dB axial ratio bandwidth can both reach 14%. For verification of simulation results, the antenna is fabricated and measured and the measured results agree with the simulated well. Polarization reconfiguration for the antenna is demonstrated well.

Abstract:In this paper, a design method of thinned concentric ring arrays base on SimulatedAnnealingbased Particle Swarm Optimization (SAPSO) is proposed. Taking the position of elements as variables, first null beamwidth (FNBW) and peak side lobe level as fitness function, the convergence velocity of the method is improved and the local optimum can be effectively escaped combined with the advantages of the simulated annealing algorithm and the particle swarm optimization algorithm. The simulation results demonstrate that compared with the existing four popular methods of thinning concentric ring array, the first null beamwidth of the obtained thinned array is retainable equal to that of the full array and the peak side lobe level is reduced considerably.

Abstract:Based on the importance sampling (IS), this paper proposes a new algorithm to estimate the time delay and amplitude in multipath channels. This algorithm decouples the time delay and amplitude estimation and utilizes Monte Carlo method for sampling unknown parameters. By so doing the parameters are approximated by the average of samples, and the estimator proposed in this paper avoids the complex multidimensional grid search and iterative methods which depend seriously on the initial guess. The results show that the algorithm performs well under condition of respective multipaths 5, 15. Compared with some other known algorithms under the same condition, the algorithm can achieve not only the time delay estimation, but also a precision amplitude estimation simultaneously.

Abstract:In order to obtain the relaxation time of the resistor array infrared decoy transformation, and to settle an idea for improving transformation speed of patterns through testing and analyzing the temperature variety characteristics of different resistors, a conclusion is as follows: Among familiar resistors, metalfilm resistor has the shortest relaxation time in increasing and decreasing temperature which is approximately 30 s. Two kinds of constantan resistance wire's relaxation time are longer than Metal film resistor's, the time of increasing temperature extends about 22.4%, and the time of decreasing temperature extends about 43.9%, the relaxation time of increasing and decreasing temperature of glazed wire wound resistor and Ceramic wire wound resistor are relative longer, which more than 100 s.One resistor has about the same relaxation time under different voltages. The relaxation time of cooling is longer than that of temperature rise to the same resistor. To shorten the relaxation time of temperature variety and improve patterns' transformation speed, the resistor and the dielectric material must have small mass and heat capacity.

Abstract:Aimed at the problems that the edge is fuzzy and the visual effect is poor during the fusion of the infrared and visible images, a fusion algorithm based on NSCT is proposed. NSCT has shiftinvariance and a good direction selection, only thus can the algorithm fully capture the contour and more details of the image. Firstly, the NSCT is used to take multiscale, multidirection decomposition for the infrared and visible image, and then the edges of the low frequency image is extracted by using the isotropic Soble gradient operator ,and fused the low frequency coefficients by edge information to attain the low frequency fusion image. Meanwhile, the high frequency coefficients are fused by region energy to attain the high frequency fusion image. Finally, the fusion image is reconstructed by performing the inverse NSCT on the low frequency fusion image and the high frequency fusion image. The simulation experiments according to both the subjective and objective criteria ,including the information entropy ,space frequency and average gradient, show that the algorithm can get a good fusion image with more clearly details such as edges. Besides ,the fusion image is more conform to the requirements of human vision.

Abstract:Measurement device independent quantum key distribution is immune from all the detection attacks, so the final key is unconditional secure combined with the decoy state method. This paper analyzes statistical fluctuation analysis of finite key for the yield of single photon and quantum bit error rate of measurementdeviceindependent quantum key distribution by adopting the law of large number, and simulates the yield of single photon and the key rate by changing the key (N=106~1012). The result indicates that the secure transmission distance in optical fibre transmission will decrease to 260 km and 75 km respectively with the reduction of the key length, and the secure transmission distance comes to 295 km , which is close to the limitation when the key reaches to N=1012.

Abstract:Aimed at the shortages of existing service migration strategies, a proactive service migration model based on network survivability situation awareness is proposed. First, network survivability situation awareness is evaluated by using intrusion detection and failure detection timely, and under these circumstances, a service migration trigger mechanism based on network survivability situation awareness is designed. Then, a new concept "mainlysecondary server" is proposed, and service migration model is found combining directional and random ways, and correlative algorithm is researched. The results show that this service migration model improves not only survivability, but also reduces service break off time largely. And at the same time, this model is the guarantee of continuous and trusty run of service under conditions that something unexpected happens suddenly.

Abstract:The digital pulse width modulator is one of the core modules in the digital switching power supply, its linearity is an important criterion to measure the digital pulse width modulator，and，of course，is also a major problem. In order to improve the linearity of the digital pulse width modulator, the paper proposes a calibration function of hybrid structure based on the times of capacitor charge and discharge, and discusses the working mechanism of the hybrid structure in detail. When system clock is 32 MHz, the digital pulse width modulator is realized that switching frequency is 1 MHz and resolution ratio is 10bits. The design for each module circuit is based on SMIC 180 nm technology to do postsimulation, compared to linearity of hybrid digital pulse width modulator based on counter and the delay line structure. The results show that the linearity based on capacitor charge and discharge with the digital pulse width modulator with calibration function is improved, and DNL is 0.125 LSB.

Abstract:The stochastic duel models between two forces that on one side all members have ability to attack and on the other side some members do not have the ability to attack are established. Under the condition of stochastic aiming, the differential equations of state probability of the grouped and not grouped offensive side are established. Under the different combat termination decision rules, the algorithms for the probability of wining of the grouped and not grouped offensive side, the probability of successful defense of defense side and the probability of the draw of two side based on recursive formulae are given. In the cases that offensive side grouped, the properties of the probability of winning are proved under the conditions of different combat termination decision rules. Different combat termination decision rules result in a very different property of probability of winning of offensive side. Through the concrete numerical example probabilities of winning with different parameters of the grouped and not grouped offensive side are compared. The results show that there is not a attack scenario which is the absolute dominant.

Abstract:The problems of the arch structure dynamic buckling subjected to explosive impact are studied by numerical simulation method. The influence of the arch rise span ration on the dynamic response and the dynamic buckling is analyzed mainly. The results show that when the rise span ration of the arch is more than 0.1, the maximum displacement point is the arch top in the elastic vibration stage at about 1/6 of the archspan after plastic deformation occurring. When the impact duration changes in a certain range, the counterintuitive response appears after buckling. There are two corner points in the displacement amplitude vs. load amplitude curve of the arch top. The load corresponding to the first corner point can be seen as the dynamic buckling critical load, and the other corresponding to the second corner point can be seen as the dynamic failure load. When the rise span ration of the arch is less than 0.1, the counterintuitive response doesn't appear after buckling. The dynamic critical load is namely the dynamic failure load. When the impact duration comes to a certain degree, the smaller, the rise span ratio of the arch structure, and the smaller, the dynamic buckling critical load.

Abstract:The hybrid operations of surfacetoair missile is an necessary choice of dealing with information air attack and improving groundairdefense integrated operations effectiveness. The basic mode and criterion of surfacetoair missile hybrid deployment are explained. The main factors of deployment decision model are analyzed based on System Dynamics (SD) theory, including the airattack parameters, firepower unit deployment and equipment capabilities. The judgment regulation of fire condition, variable setting and inflection relation in SD simulation model are proposed. Taking "one intermediate and two short range" hybrid deployment mode as an example, the SD model of surfacetoair missile hybrid deployment decision is built, including the model structure diagram and important variables operation relation. By setting the typical parameters and countermeasure sequence, the SD model simulation experiment is executed and the important variables' simulation results are acquired. And the meaning and application of simulation results are discussed. The case application shows that the decision SD model is feasible and effective.