Abstract:Soft intelligent materials can produce different deformation under some external stimuli (such as temperature, electricity, light, magnetic field, and so on) to demonstrate the activities. As the representative of the new intelligent soft active polymer materials, shape memory polymer and electro active polymer are showing significant potential. In the review, the actuation methods, applications of SMP in the aerospace field and its composites are introduced; in addition, the recent progress of theoretical studies and aerospace applications of dielectric elastomer are summarized.

Abstract:For curve skeleton extraction algorithm, in order to improve the efficiency of potential field computation and save the time of extraction process, we presented a parallel potential field skeleton extraction method to reduce the time complexity, which was suitable for implementation on GPU, and then improved it by using constant memory and shared memory which was unique in CUDA. In order to achieve the highest GPU occupancy and the best speedups, we discussed how to assign threads according to the property of program and graphics device. The implementation was tested on several complex 3D models in CUDA framework. The results showed that our method had excellent performance especially on large data scale. When processing the volume data with the scale of 256×256×487, this improved method achieved speedups of 18x.

Abstract:To overcome the problem of high computational cost of active contour model, a new local region-based active contour model in a variational level set formulation for image segmentation is proposed. An energy function based on the region-scalable fitting (RSF) term and the Kullback-Leibler divergence term is formulated. The existing methods construct the energy function for segmentation through computing the distances among the intraregion points and the ″ center″ fitting this region, representing similarity of object region. An energy term including the disparity measured by Kullback-Leibler divergence between regions to be segmented is added to the energy function of the RSF model in the proposed model. The model can handle blurry boundaries and noise problems. The proposed method is applied to segment synthetic and real images, and the experimental results show that KL-RSF can improve the effectiveness of segmentation while ensuring the accuracy through accelerating the minimization of the energy function.

Abstract:In order to meet the requirement of high-speed and high-order shaping filter design, an improved DA (Distributed Architecture) algorithm is proposed on the basis of the traditional DA method. Considering zero insertion using in up-sampling process, Look-Up-Table is employed instead of ROM (Read-Only Memory) for reducing the number of effective address and increasing addressing speed. The proposed algorithm takes advantage of tables segmentation and symmetry of filter coefficients to save storage resource and improve processing speed. Meanwhile, pipeline contracture is further exploited to achieve better performance. Compared with commercial finite impulse response filter IP core, the proposed algorithm not only realizes higher rate as well as reduces the utilization of logic resources effectively, but also can design high-order filter without limit of ROM in hardware.

Abstract:Complex clutters of High Frequency Surface Wave Radar cause difficulties on target detection. Based on polarization characteristics of HFSWR, a new method by combining polarization information with the traditional dynamic programming algorithm is proposed. Moving target direction information and polarization information are used to improve the performance of the algorithm, and pre-detection technique is adopted to reduce the amount of calculation. The simulation and test results in a Gaussian background and HFSWR measured data show that the new algorithm based on polarization information has significant performance benefits compared to the traditional method based on dynamic programming algorithm in the ionosphere clutter.

Abstract:The probability estimate method of SLWE can adapt to the non-stationary data. In order to expand its application in entropy coding and code non-stationary data more effectively, an application scheme of SLWE in the range coding is designed. Firstly, to tackle the problem how to map the estimated probability by SLWE to the coding interval, instead of calculating the update probability, we propose to update the range of every character directly based on the idea of SLWE and then adjust the total range according to the computing method of the upper and lower range bounds for range encoding. It not noly combines the advantage of SLWE to cope with the non-stationary data, but also avoids the probability calculation. In addition, the coding range after the update for every character may be less than 1, which causes the loss of the character. To solve this problem, we present a control method to set the minimum range of each character. Experimental results for non-stationary data coding show that the SLWE-based range coder achieves 1%~5% higher than that using traditional probability estimation (e. g. windowing method) in terms of compression ratio.

Abstract:For the purpose of conformal array resolution performance, the signal model of conformal arrays(conical conformal array, cylindrical conformal array, spherical conformal array) are built in this paper, and polarization-DOA estimation is realized based on MUSIC, through the definition of MUSIC null spectrum and expectation of noise subspace projection matrix. The expectation of MUSIC spectrum and the resolution threshold of MUSIC for conformal array are derived in detail. The resolution threshold relationship between theory and simulation, conformal array and uniform circle array are studied by computer simulation. Simulation results show that resolution threshold of conformal array is reduced gradually with the increment of SNR, and the correctness of theoretical analysis is certificated by the simulation.

Abstract:To overcome the difficulty of reaching a balance of throughput, fairness and packet loss of current LTE scheduling algorithms, an enhanced algorithm is proposed. We take the Resource Block (RB) utilization into consideration on the premise of considering user delay, and hence can describe the resource utilization efficiency of users more precisely, which causes the resource is allocated more properly. Simulation results demonstrate that the algorithm has a great improvement on packet loss rate, and at the same time, it performs better in terms of throughput and fairness. It shows an excellent comprehensive performance and can better satisfy the requirements of users' Quality of Service (QoS).

Abstract:To solve the problem that vector reconstruction method with uniform linear arrays cannot be used directly in uniform circular arrays, an efficient vector reconstruction algorithm based on space mode for DOA estimation is proposed. The eigenvector corresponding to the largest generalized eigenvalue of the covariance matrix is corrected to acquire signal eigenvectors after mode excitation. The receiving data matrix is constructed by the forward-backward vector reconstruction to estimate DOA of coherent signals. Optimization algorithm is presented to acquire the largest signal subspace eigenvector by performing eigen-decomposition before mode excitation, which eliminates the noise fully and avoids the generalized eigen-decomposition on the virtual linear arrays, and the computation complexity is reduced obviously. The theoretical analysis and numerical examples are provided to demonstrate effectiveness of the proposed approach.

Abstract:For precise estimation of borrowers' personal credit and reasonable risk management of commercial bank, main models as well as problems are pointed out first. Next, to solve these problems, a modified algorithm is designed to compute a series of weights for indexes to satisfy different needs in different banks with various data and finally improve the accuracy of the model.

Abstract:In order to study the Ti₂AlNb alloy superplastic forming and its performance, the materials with temperature range in 920~960℃ and rate of strain 10^-3~10^-5 s^-1 within the scope of superplasticity are studied. The results show that the material at 960℃, 1×10^-4 s^-1 when the strain rate has a good superplasticity with maximum elongation rate reaching 230% and strain rate sensitivity index 0.31. Marc software was used to simulate the three layers structure of Ti₂AlNb alloy superplasticy forming process, and the formation of defects was analysed. The analysis results show that the 1/3 of the core sheet thickness of the face sheet thickness, can effectively improve the three layers structure of surface defects; Combined with superplastic forming/diffusion bonding process, it realizes Ti₂AlNb alloy the preparation of three layers structure, and improves three layers structure surface defects by changing the core sheet and the thickness of the face sheets. The results show that using reasonable technology and process parameters can achieve the preparation of hollow sandwich structure of the alloy.

Abstract:Security and protection for process is a hot point in the field of information security, which can be applied to computer security system, anti-virus software, the protection of digital property rights, etc. In the context of information security, this paper summarizes the threats of the process including software threat and hardware threat, and combines the actual case. It classifies the security protection technology for process from hardware and software aspects, as well as analyzes the characteristics of each technology and its shortcomings. Finally the paper concludes the problems in the current research, and looks forward to the future research direction and focus on security protection technology for process.

Abstract:To resolve the problems of high computational complexity, low anti-noise ability and the drifting of pixel position, a scale invariant feature algorithm based on causality is proposed in this paper. Firstly the Gauss smoothing image is built up by Gaussian convolution with the original image. Then, the Harris corners are extracted as candidate features both in the original and the Gauss image. Finally, the stable scale invariant features are acquired by projection from the original image to the Gauss image. The experimental results indicate that this algorithm is concise, fast, efficient with strong anti-noise ability, and provides a basis for subsequent visual processing.

Abstract:A 3D image calibration method is proposed to provide a better performance on particular display device. Firstly, the knowledge of stereo image fusion area is adopted to calculate the comfortable horizontal disparity range for different display device. Secondly, the Scale-Invariant Features (SIFT) algorithm is applied to estimate the disparity range in a 3D image, and then a linear mapping between the original disparity and the comfortable disparity for the 3D image are obtained. Finally, the transformational matrix for the linear mapping and disparity correction for the 3D image are got. The experimental results indicate that the proposed algorithm has a good performance, which is adaptive for various disparity problems.

Abstract:To improve the TAC resistance to ciphertext and selective plaintext attacks, a novel security arithmetic coding scheme based on M-ary symbol is proposed.It combines data encryption with compression.The modified arithmetic coding methodology changes the encoding interval and codeword of TAC by using an encryption key to alter the symbols orders in the encoding interval.Simulations both on static and adaptive model show that M-SAC can obtain higher SER than BRAC when decoding with a wrong key.The proposed encryption algorithm satisfies highly security without loss of compression efficiency, which has strong resistant to ciphertext and selective plaintext attacks.

Abstract:To improve the robustness of the communication system in complex underwater acoustic environment, the hybrid carrier system based on WFRFT was put forward. To obtain the optimal transformation order, the hybrid carrier system is designed with the lowest bit error rate as optimization goal. Simulation results show that BER performance of hybrid carrier system is between the traditional single/multi carrier systems in multipath channels. However, system performances with the optimal order are superior to single/multi carrier systems under the doubly selective fading channels. It has the excellent characteristics of the single/multi carrier systems and it is thus prospective in improving the robustness of the communication system.

Abstract:In order to improve the performance of PPM demodulation system, we proposed an improved digital phase-locked loop to extract slot synchronization clock and a fast frame synchronization extraction scheme. On the basis of traditional digital phase-locked loop, the digital filter and FIFO buffer unit are added. The results show that the slot synchronization clock can be precisely adjusted. The adjustment accuracy is 0.25π. The jitter of slot synchronization clock is only 1.5 ns in 10 Mbps. Finally the system achieves atmospheric laser communication in 10 Mbps.

Abstract:We propose a service evaluation method based on risk preferences (SEM-RP) for the risk caused by quality volatility. First, complete description rating information according to the interval number theory is made. Then we use risk preference to identify user's perceived risk in order to express different user's risk propensity. After that, service revenue is obtained by calculate service attributes and users' preferences according to the principle of revenue maximization, and finally we get service evaluation rating by calculate service revenue and user's perceived risk. Simulation experiments and results demonstrate that the proposed method can clearly express the characteristics of user's risk preference while expressing user preferences attributes and which have the performance of higher user satisfaction.

Abstract:In order to improve the throughput of multichannel CR, a joint allocation of spectrum sensing time and subchannel sensing threshold based on the alternating direction optimization is proposed. Based on the SU's listen-before-transmit frame structure, an optimized allocation model is built to maximize the aggregate throughput of the SU over all the subchannels, providing that the communication demand of the PU and the performance of the subchannel spectrum sensing are guaranteed. The joint optimization algorithm is proposed to obtain the optimal solutions to the model through alternately optimizing sensing time and threshold. The simulation results show that there exist the optimal sensing time and threshold that maximize the SU's throughput, and compared to the previous schemes, the joint allocation can improve the SU's throughput.

Abstract:For this purpose of the rapid and effective scene interpretation for remote sensing big data, a novel method for feature representation is presented. First of all, the corresponding filter banks of local training samples in image are obtained by unsupervised learning. The feature map of scene units is then quantized based on binary hashing coding. Finally, the global feature of scene is obtained from statistical results. The experimental results demonstrate that, combining with both the advantages of filter bank and binary feature descriptor, the proposed feature can greatly enhance the computational efficiency on the assumption of ensuring high accuracy, which has shown its robustness.

Abstract:Considering most advanced LANDMARC algorithms based on passive RFID mainly aimed at enhancing the accuracy of the localization but neglecting the long time consumed in reading tags because of the by half-duplex mechanism, we leverage the distance loss formula and put forward power level model based on the radiation radius. After analyzing the influences of the maximum power grades of the RF reader and the arrangement density of the reference tags, an evaluation method of localization is proposed for the passive LANDMARC algorithm. Simulation results in a wide range of environments showed that the proposed method has the good stability and practicability. The method also makes sense of system evaluation and parameter selection for the passive RFID Localization Algorithms.

Abstract:In order to solve the problem of the high complexity of channel encoding/decoding algorithms and real equipment for the networking coding system with LDPC code or Turbo code in two way relay channel, a new combination scheme of Polar channel code and physical network coding is proposed. This scheme utilize the superposition of wireless signals and the linear property of Polar code and network coding to estimate the network codeword directly, thus reduce 50% the decoding complexity of relay node and 50% the information exchange time between source nodes than that of the direct network coding. Simultaneously, Polar code which based on the channel polarization can achieve channel capacity on BDMC with low complexity of encoding and decoding algorithms, so the proposed scheme can be applied easily with reliability, and the simulation results also verified the effectiveness of the scheme.

Abstract:To solve the problems of slow convergence speed, low search precision and poor robustness in traditional double chains quantum genetic algorithm, a new double chains quantum genetic algorithm (F _DCQGA) is proposed. The coding space is mapped to reduce the algorithm searching space and increases searching density, under the premise of guaranteeing quantum population adaptation and argument population monotonicity. The adaptive step-length factor is introduced to the quantum updating, which changes the step-length with gradient of objective function in searching points. This could solve the global optimal solution search difficulties caused by oscillatory occurrence in traditional optimization algorithm. Quantum π/6 gate is presented in chromosome mutation upadating, to overcome the shortcoming that NOT gate can not update quantum bit probability amplitude. The F_DCQGA is applied to the threshold selection of wavelet threshold denoising. Simulation results show that F_DCQGA improves the convergence speed of the wavelet threshold function and searching precision. And in image edge feature extraction, the smaller mean square error (S_ME) and larger peak signal to noise ratio (R_PSN) are gained. Simultaneously, the high frequency information is also retained.

Abstract:Focusing on the lack of efficient and practical learning algorithm for Binary Feedforward Neural Networks (BFNN), a novel learning algorithm by fusing the self-adaptations of both architecture and weight for training BFNN is proposed. Based on improving the methodology of Extreme Learning Machines (ELM), the algorithm can effectively train BFNNs with single hidden layer for solving classification problems. In order to satisfy training accuracy, the algorithm can automatically increase hidden neurons and adjust the neuron's weights with the Perceptron Learning Rule. As to improve generalization accuracy, the algorithm can automatically, by establishing binary neuron's sensitivity as a tool for measuring the relevance of each hidden neuron, prune the least relevant hidden neuron with some compensation for information losing due to the pruning. Experiment results verified the feasibility and effectiveness of the proposed algorithm.

Abstract:To resolve the problems of high computational complexity and slow training in Convolutional Deep Belief Net, Convolutional Deep Boltzmann Machine (CDBM) is proposed to extract image features. To improve the Convelution Restricted Boltzmann Machine(CRBM), a new training objective function to maximize the probability of intermediate image area is proposed, along with introducing the cross-entropy penalty factor and dropout training. After that, CDBM is designed based on modified CRBM. The mean-pool mechanism is presented to lessen computational complexity and improve the robustness of features for image scaling. The relationship between layers is simplified to extract high-level abstract features. The MNIST handwritten digits database is used to test this new model and the results prove that features extracted by CDBM are more accurate than CDBN. The classification accuracy rate increase at least 0.5%, and training time decrease more than 50%.

Abstract:For CO₂ arc welding with short-circuiting transfer, the droplet transfer and dynamic behavior of molten pool are complexity and have strong randomness. Considering the random factors, such as short-circuiting time between droplet and molten pool, radius, temperature and central position of droplet at short-circuiting time, the model of droplet short-circuiting transfer behavior is proposed and set up. The three-dimensional transient model of molten pool is established for arc welding with short-circuiting transfer, after the asymmetric Gauss heat source being adopted to characterize the asymmetry of arc heat flux density along welding direction, the additional source term method being used to deal with many momentum sources, the VOF model being adopted to realize the tracking of gas-liquid interface, and the liquid volume fraction method and enthalpy-porosity technique being used to compute the latent heat of molten metal solidification and the momentum loss in the liquid-solid mush zone. Based on the secondary development of FLUENT software, the dynamic behavior of molten pool is numerically simulated; the transient evolution of the temperature field and flow field in molten pool is acquainted. The simulation results of probability density distribution of short-circuiting time interval and final weld formation agree with experimental data well, the validation of the model of droplet short-circuiting transfer behavior and three-dimensional transient model of molten pool being demonstrated.

Abstract:To reduce the aviation maintenance error rate and study the properties and rules of aviation maintenance safety information radiation on the complex network, we study the aviation maintenance safety information radiation in the maintenance personnel based on the theory of complex network. By building a safety information radiation model and defining the radiation rules between nodes through the medium of safety information, dynamic inspect the transformation of the node status in network based on changing the inherent safety degree of the maintenance personnel and the network structure. We analyze the influence of personnel proportion of different inherent safety degree and different network topology structure on the scope and period of safety information radiation when simulate the interactive between nodes on a micro level. With the help of computational simulation, it results that the different inherent safety degrees of the maintenance personnel, as well as the difference of network topology structure, have a lot of impact on safety information radiation. It is beneficial for the safety information radiation to improve the inherent safety degree of the maintenance personnel.

Abstract:In order to research the thickness distribution laws of Ti₂ AlNb alloy when it is deformed with the superplastic free bulging in high temperature, the Ti₂AlNb sheet with an uniform initial thickness, has been studied by the finite element simulation and experiment in this paper. Laws of the limit bulged samples are experimented in the 910℃, 930℃, 950℃ and 970℃. And the thickness distribution of finally bulged samples are simulated numerically with the constant strain rate. It is found that, the spherical thickness distribution is uneven after bulging; and Ti₂ AlNb sheet is bulged into irregular spherical easily; and the temperature relatively effects the spherical shape and the thickness as well. The temperature can affect the thickness distribution of Ti₂ AlNb alloy sheet formed by superplastic free bulging, based on which the temperature sensitivity index n is considered to correct the E-K model which predicts the thickness of the bulged sheet. The study provides a reference basis for the superplastic deformation of complex thin-walled structures in aerospace of Ti₂AlNb alloy.

Abstract:To solve the problems of premature convergence and weak ability in global search of the genetic algorithm, a fitness sharing niche genetic algorithm based on extenics is proposed.The algorithm build the matter-element code and extension genetic operator, create niche groups by extension clustering, and preserve the stability of niche groups by combining fitness sharing mechanism and elitist retention strategy. Experiments show that the algorithm can solve the optimal performance with global search ability and fast convergence rate. It is proved to be more effective and accurate than standard geneic algorithm and normal niche genetic algorithm.

Abstract:Focused on the application of special-shaped joints, 0Cr18Ni9 stainless steel pipes were brazed using BNi82CrSiB (BNi-2) as filler alloy to form a bell and spigot joint. Influences of cooling-down velocity, brazing temperature, holding time and fit-up gap on the microstructure and mechanical property of joints were investigated. Results indicated that the fit-up gap had a great effect on the joints due to the special structure of pipe joints, when the width of gap is only 5~10 μm, it is difficult to fill the lap to form a complete joint and the strength of joints is low, but if the gap is too large up to 250~300 μm, large amounts of brittle phases formed in the brazing seam as well as micro-cracks. Cooling velocity almost made no difference on the microstructure, while the joints cooled at 15℃/min present lower strength than that furnace cooled. Increasing brazing temperature or prolonging holding time, the maximum gap increases and erosion of the matrix can be observed, but both parameters have few effects on mechanical property. When the two pipes with the fit-up gap of 20~50 μm were brazed at 1 050℃ for 10 min and furnace cooled, no eutectic phases and intermetallics appeared in the seam, and the strength of the joint reached the maximum.