Abstract:A bearings-only system is considered to be observable if, and only if, the target motion parameters can be uniquely determined by bearings-only observations. The problem of observability for bearings-only target location is discussed in this paper based on the target traveling in the three-dimensional space at a uniform velocity. The vector-graph between target and observer is drawn and vector equations are founded, by utilizing Gramme rule and rank of matrix, the observability of the observer with a uniform velocity and a uniform acceleration is obtained. It is shown that the target is unobservable toward observer with a uniform velocity as the observability index is a constant; the target is observable if the observability index is not a constant toward observer with a uniform acceleration. The study done in this paper is valuable to solving the bearings-only target observability analysis and it is of constructive sense to producing optimal trajectory of the observer.

Abstract:Air attack formation is a tactical group formed by the airplanes in different combat missions, the distribution of it is an important basis for the air defense commander to analyze the purpose of the enemy air attack and make the campaign decision. The air attack formation possesses the following characteristics: large in airplane quantity, great in distribution range and needs a rapid analysis of enemy's situation. According to the air target's data characteristic, a method and steps for classifying the air target group based on dynamic clustering technique are established. This algorithm has a better astringency and can meet rapid analysis demand for command and control system. Based on this, an algorithm for calculating the campaign parameters inside the target group and among the groups are put forward and an analysis model of the enemies' primary air attack direction and attack purpose is presented according to the attack formation quantity distribution and fairway shortcut. Finally, a material example is put forward, and the result is identical with the commander's judgment on the whole. In engineering practical application the air target can be fast clustered by using this model, which can provide a quantitative foundation to the region air defense commander in control of the air situation accurately and making decision quickly.

Abstract:Engine rig tests are performed and compressor passage flow pressure signal at surge boundary is obtained. Spectral analysis is adopted to investigate passage flow characteristics at surge boundary. Among all the frequency contents of the pressure signal of the first compressor stator passage, compared with higher rotor speeds at which the flow matches well, the magnitudes of BPF1 and BPF2 the blades are passing frequency contents for the first two compressor rotors respectively and the magnitudes of harmonic frequency contents near 550 Hz increases obviously at surge boundary, and a few spectral lines with very high magnitudes appear near 550 Hz. In the process of reducing rotor speeds from high speed, the magnitudes of BPF1 and BPF2 rapidly increase at first, and then gradually decrease; while the intensity of the frequency contents near 550 Hz gradually increases with the decrease of rotor speed. As for the test engine, the passage flow characteristics at surge boundary might be helpful to the monitoring and early-warning of compressor operation stability.

Abstract:With the methods of real warhead explosion experiment and numeric simulation etc, the mechanism of trough damage in the airplane by discrete rod is discussed. The effect of the rod's size, velocity on airplane structure damage is discussed. The correlative computing formula is established to forecast airplane structure battle damage. The reason that causes the error between numeric simulation and real experiment is analyzed. The research result is useful to airplane battle damage forecast, evaluation, establishing ABDR prefab plan and survivability design. The results show that as long as the rod has enough speed and the yaw is bigger than 0??, the long penetration damage (trough damage) will be formed on the flat. Because of the damage expanding in the rod penetrating process, the damage width is bigger than the diameter of the rod. When the flat isn't put on the ground vertically, the rod's velocity is vertical to the ground and the yaw is 90?, the trough damage size is longer than the length of the rod. In this condition, an appropriate decrease of flat's yaw can cause the increase of the trough damage.

Abstract:The compaction quality of filling is very crucial to high-fill airport construction. In recent years the vibration compaction and impacting compaction are two common compaction methods for treating the stone filling of high-fill airport, and they have different working capability. For treating the stone filling of high-fill airport in southwest mountainous areas, the methods of vibration compaction and impacting compaction are adopted to perform compaction test, furthermore, the economic effect and the compaction results of settlement observation、compacting degree test are compared and analyzed synthetically in order to determine an appropriate treating method and working parameters. The experiment results indicate that the economic unit price of the impacting compaction is a bit higher than that of the vibration compaction, but the treating effect of it is better than that of the vibration compaction for this project: the valid effect depth of the vibration compaction is 60cm, and the biggest compaction degree is only 90.3%; the valid effect depth of the impacting compaction is 120cm, and the compaction degree of 93% can be obtained when treating 20 to 30 times, what's more, the treating speed is faster. Thus, the impacting compaction method is taken in use and the reasonable working parameters are defined, which bring both a good compaction effect and an obvious economic benefit in the project practice.

Abstract:The Structure of Radar Side-Lobe Cancellation (SLC) System is determined by its capability measurement rule and the corresponding algorithm, SLC is one of the key techniques in the enhancement of radar electronic war capability. To improve the convergence speed and stable state capability of the algorithm in radar SLC, an improved un-constant-step LMS algorithm based on S-function is put forward aimed at the general problems (low convergence speed and poor stability) existing in the un-constant-step LMS algorithm. The simulation results show that this system can fast restrain the jamming, effectively improve the system Real-time and stable state capability. And the experimental verification is done based on the requirements of the real application circumstances, the result shows that: when two coherent jamming source and the inner noise of receiver are in existence, the application effect of double CSLC is better than that of single CSLC.

Abstract:Due to the good learning and generalization performance, the SVM （support vector machine） has been widely used in practice. But, how to make the SVM more effectively perform incremental learning is a problem that needs to be solved in the present application of the SVM. The distribution characteristics of Support vectors are studied and a novel improved incremental SVM learning algorithm-distance ratio algorithm is proposed. According to the removing rules of the proposed method, an appropriate parameter is set and samples that have less effect on later training are abandoned. According to the definition in distance ratio algorithm, the ratio between the center distance of each sample and the distance of each to the optimum classification surface is calculated. In this way, the training data sets can be effectively reduced. Experiment on standard data sets shows that by using this method the classification accuracy can be guaranteed and the training speed can be effectively improved.

Abstract:For improving target's location accuracy and fully utilizing redundant information in complex bistatic radar systems, a new target location algorithm based on Gauss-Newton iterative is proposed. The key features of the algorithm are as follows: All the observation data from transmitting station and receiving station are adopted to compose a nonlinear least square equation, the location estimation resolved by a measurement subset which has higher accuracy among all subsets is utilized as an initialized value, which is close to the truth value. The idiographic flow about iterative algorithm is constituted and the strategy of changing the iterative step size is introduced so that the objective function is dynamically declined. Moreover, expressions of location error covariance matrix are deduced and the target's location accuracy is analyzed. Simulation shows that by using the algorithm, the iterative convergence and veracity of target location are improved. This algorithm, as compared with the SWLS algorithm, has more accurate target location solution. In this way, the location accuracy in the whole detected area is greatly enhanced and the capability of target location is optimized.

Abstract:Based on the command relationship in unified air defense, firstly, three typical command organization structures are built. From the point of view in command information transmission, according to the selecting principle of evaluation index, and in combination with the factors influencing the command organization structure rationality in unified air defense, an index system of the command organization structure rationality is put forward, and a measure model of index is also established. Secondly, with the application of grey clustering theory, the evaluation method of unified air defense rationality is discussed, and the calculating steps are presented. Finally, an analysis of the examples of the three typical command organization structures is given, and the result shows that this method is simple and feasible.

Abstract:A new method is given in this paper in order to evaluate the air-to-air missile (AAM) infrared countermeasures (IRCM) performance, the method can be used in detecting IR missile in the assessment phase. By using this method, IRCM tests are analyzed and programmed first, then each missile IRCM test is decomposed into seeker IRCM test and guide & control (G&C) IRCM test in order to measure test data accurately. The resource categories of seeker IRCM test include digital simulation (DSM), hard-in-loop simulation (HTIL), installed systems (ITLS) test and launch test, the resource categories of G&C IRCM test include DSM, HTIL and launch test. By hierarchical Bayesian analysis method the seeker IRCM probability model and the G&C IRCM probability model are deduced, then by Second-moment-equivalent assessment of serial reliability the missile IRCM probability is got. In comparison with the traditional evaluation method, the method discussed in this paper is reliable and precise, and by using it the confidence interval of the AAM IRCM probability can be obtained.

Abstract:With the environment in aerial defending becoming increasingly complicated, it is very important to recognize the target fleetly and exactly. Multi-data fusion provides a new idea in target recognition. Information fusion can be performed at pixel level, feature level or decision level. Dempster's rule plays a potential role in auto-recognition of target, to solve the problems in the application of the evidence Theory, this paper analyzes the principle of Dempster's rule and then discusses its limitations and amendatory measures, including amending evidence source and modifying fusion rule. Finally, the paper proposes a general method for air target identification and presents the flow chart of the identification process. Through simulation and the comparison of it with other algorithms，the results show that the proposed algorithm is more efficient and feasible.

Abstract:A differential detection method is proposed for M-ary spread spectrum signal process. The serial input data is converted into parallel data before M-ary differential encoding, M-ary spread spectrum modulation and carrier modulation. The influence of combination-correlation interference and the selection difficulty of M-ary spreading codes can be decreased by employing the presented Modified Cyclic Spreading Codes (MCSC). The MCSC is composed of three parts: cyclic prefix, the prototype spreading code and its cyclic postfix. The proposed receiver can achieve M-ary de-spread spectrum with only one chip SAWTDL device, which reduces the complexity of receiver effectively. Based on the coding rule, the interval between neighboring autocorrelation peaks loads the transmitted information which can be restored by M-ary differential decoding. The BER performances and data transmission capability of the system are analyzed. The conclusion drawn from computer simulation is identical with the theoretical analysis.

Abstract:A virtual implementation method is proposed to emulate the effect of passive piezoelectric shunt damping. A controller having a set of second-order dynamic equation and measurement equation is designed and the feedback structure according to the LR series shunt circuit is developed by using the governing equations of piezoelectric shunt damping system, the set of equations does not represent any physical system, the inductor and the resistor only "exist" as numerical representations inside the controller, the closed-loop control system is stable or asymptotically stable. The virtual implementation method can both eliminate the need for large inductor and adjust circuit component parameters online to adapt to environmental changes, therefore the two disadvantages of the physical piezoelectric shunt damper are overcome, also the feedback gain can be adjusted to implement the a better vibration control effect than the physical piezoelectric shunt damper. The simulation results for a cantilever beam show the effectiveness of the virtual piezoelectric shunt damper for vibration suppression.

Abstract:In order to improve the accuracy of ground angle guiding equipment in Microwave Landing System，based on microwave linear phased array antenna theory, the main factors of causing phased array antenna beam to point error and the errors produced by floor phase feeding in different Quantization steps are analyzed. Beam pointing errors obtained from floor phase feeding and from randomizing phase feeding by using 4-bit Phase Shifter are compared. Through simulation, two randomizing phase feeding methods are particularly discussed and analyzed. The periodic error is eliminated by using these two methods and consequently the phased array antenna beam pointing accuracy is improved especially by Appropriate Random Phase Quantization. The simulation results indicate that beam pointing error is significantly decreased and the location accuracy is greatly improved.

Abstract:Aimed at the problems, of analysis on band gap of electromagnetic crystal using usual method, such as time-consuming, hard to be understood, a model of plane wave expansion （PWE） method is introduced in this paper and the plane wave expansion method is adopted to analyze the band gap structure of two-dimensional electromagnetic crystal with different shape of filling cell. By using this method, electrical field or magnetic field and dielectric constant or its reciprocal are expanded in the form of double Fourier series, which are then substituted into the scalar wave equation they must fulfill. Again, a characteristic equation for 2-D electromagnetic crystal is achieved, and by solving it the band gap structure is obtained. Moreover, two equivalent structures are introduced. The results of calculation show that the size of filling cell and the relative dielectric constant all have influence on band gap structure. Comparison between the numerical solution and literature data indicates that the method in this paper is valid. At last, two equivalent structures are obtained by using periodic prolongation. It is not required to deduce the structure coefficients, and the analysis of band gap structure using the model of plane wave expansion method is realized, so simplification of analysis is achieved.

Abstract:Antenna is one of the most important parts of wireless communication and detection system, whose functions, tasks, configuration and weight are highly required in the study of mobile and space communication fields. The integral performance of the system would be highly improved for that the conformal array antennas will be used widely in the future aircraft, mobile communication and sonar, etc., fields. WSF (Weighted Subspace Fitting) algorithm, a classical high resolution method（DOA）, is replanted into the cylindrical conformal array antenna through modeling its 3D steering vector in this paper. The estimation variance of WSF and CRB for cylindrical conformal array antenna are carefully derived, and finally the performance and effect of DOA of bearing estimation is analyzed via computer simulations. The estimation results are gradually reached CRB shown in the computer simulations with the increasing of SNR and elements in matrix.

Abstract:Left-handed meta-materials can be fabricated by combining electric resonators with magnetic resonators to realize simultaneously negative permeability and permittivity, so the design of magnetic resonators is of great importance in designing new types of left-handed meta-materials. Dealing with the design of magnetic resonators, the design principle of magnetic resonators is proposed. The structure of the magnetic resonator must be equivalent to a mirror-symmetrical single loop in order to eliminate the unwanted bi-anisotropy. Based on the design principle, a coupling-enhancement magnetic resonator structure is devised. The negative permeability of the structure is verified by experimental simulations. The results show that the permeability of the structure is negative in 8.9GHz~10GHz and that bi-anisotropy is eliminated effectively. Compared with the conventional magnetic resonator SRR, the proposed magnetic resonator is simple in structure and much easier in fabrication and analysis.

Abstract:In the equipment developing stage, the expense of equipment developing cost is an important part of the equipment life cycle cost, and has a significant influence on the whole life cycle cost, this paper presents a new model which can help the decision-maker accounting the expense of equipment developing cost. In light of Vague sets, the meaning and fuzzy entropy of Vague sets are described. Based on the characters of Vague sets that can deal with the fuzzy information exactly, a new annuity distributive model of equipment developing cost is advanced. In using the model, the judgment matrix is first established by the experts, and then handled quantitatively. Based on the results obtained the fuzzy entropy of Vague sets is calculated. Finally, the fuzzy entropy of Vague sets is used to determine the development cost of equipment weights and the amount of annuity. A practical example shows that the model is reasonable and effective. This model can be used as a reference when decision makers distributing capital, so it is of a certain practical value.

Abstract:There are several suppliers we can choose in purchasing equipment。The study of the theory in qualification judging and standard defining for suppliers is the key to choosing a supplier。Based on the instinct fuzzy set and the improvement on it, this paper presents a synthesis judging model of multi-attribute decision-making, which will provide a basis of quantitative analysis for the equipment purchase decision-makers and help them make a right decision，and also can offer some valuable advice on the problem of supplier choosing in the invite public bidding。The application of this theory makes the results of the synthesis judging model of multi-attribute decision-making become more reasonable and scientific. In a word, this paper discusses the problem of the supplier qualification judging based on the theory of the instinct fuzzy set, then gives an example of the supplier choosing, and the results indicate the validity and feasibility of the model.

Abstract:The piezoelectric ceramics Pb(Zr0.52Ti0.48)O3 (PZT) are prepared by traditional solid-synthesis. The Effect of PbO on Properties of Pb(Zr0.52Ti0.48)O3 Ceramics are studied. The effect of PbO in different content on phase structure and microstructure of PZT ceramics are investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The phase structure of PZT will not be affected by PbO (perovskite) in excessive content. When the content of PbO is more excessive, the phenomena of over sintering and pore will appear. PZT+0.5mol PbO is optimized crystal. The density、 dc resistivity、 piezoelectric and dielectric properties are measured. The results show that the optimum composition is PZT+0.5%molPbO which have good dielectric and piezoelectric characteristics by pre-sintering at 850℃ and sintering at 1 250℃. The maximum value of piezoelectric constant d33 is found to be 322 pC/N.