The paper mainly presents the design of beam-wave interaction of a C-band high-peak-power high-efficiency broadband klystron. The beam-wave interaction section is designed based on considerations of efficiency and bandwidth synthetically. As a part of beam-wave interaction section, buncher section is simulated by Particle-In-Cell (PIC) code to observe the bunching process of electron beam to achieve high conversion efficiency of electron beam and RF field. When it comes to the other part, output circuit is designed as a three-section filter by an output cavity loaded with Chebyshev filter, and the cold test results are given. The beam-wave interaction is simulated by EGUN code and Arsenal-MSU code respectively. The simulated results indicated that, the existence of power dips in the operating bandwidth is verified by Arsenal-MSU code, comparing proper results by EGUN code. Then, the method that design parameters are not adjusted except parameters of buncher cavities to remove potential power dips is described. What is more, the simulated results of electron optics system are given by EGUN code and Arsenal-MSU code respectively. The further hot test results of klystron prove that the whole design of beam-wave interaction is effective.
Based on the observation that both subthreshold and gate leakage depend on transistors width, this paper introduces a feasible method to fast estimate leakage current in buffers. In simulating of leakage current with swept transistor width, we found that gate leakage is not always a linear function of the device geometry. Subsequently, this paper presented the theoretical analysis and experimental evidence of this exceptional gate leakage behavior and developed a design methodology to devise a low-leakage and high-performance buffer with no penalty in area using this deviation.
Phased array radar has been applied broadly because of its sound performance. But signal of phased array radar is of a wide variety of types. Therefore, recognition of phased array radar is the most puzzling aspect of the whole emitter identification domain. To solve the problem, the article proposes the method that identifies phased array radar by pulse amplitude information, and studies the phased array radar, models transmit signal of them, and receiving signal by radar countermeasure reconnaissance receiver. From constructing template of pulse train’s amplitude vector of mechanical scanning radar, computing distance of samples and standard template, finding threshold of the template matching arithmetic, the article puts forward the template matching algorithm of radar beam scan type recognition to identify phased array radar automatically.
It is a hot issue in communication research field to select the best network for Heterogeneous Wireless Networks (HWNs), and it is also a difficult problem to reduce the handoff number of vertical handoff. In order to solve this problem, the paper proposes a multiple attribute network selection algorithm based on Analytic Hierarchy Process (AHP) and synergetic theory. The algorithm applies synergetics to network selection, considering the candidate network as a compound system composed of multiple attribute subsystems, and combines the subsystem order degree with AHP weight to obtain entropy of the compound system, which is opposite the synergy degree of a network system. The greater the synergy degree, the better the network performance. The algorithm takes not only the coordination of objective attributes but also Quality of Service (QoS) requirements into consideration, ensuring that users select the network with overall good performance. The simulation results show that the proposed algorithm can effectively reduce the handoff number and provide uses with satisfactory QoS according to different services.
This paper concentrates on the data processing of Frequency Modulation Continuous Wave (FMCW), Synthetic Aperture Radar (SAR) in the case of wide swath and squint mode. In the mode, the Doppler centroid dramatically varies along slant range compared to conventional pulsed-SAR. This poses a challenge for system design and signal processing since a very large azimuth bandwidth would be introduced. In the paper, we accommodate the Doppler centroid variations with range by an improved spectral-length extension method, where a bulk range shift and updated Doppler centroid variations are introduced to greatly reduce the azimuth aliasing with respective to the existing methods. Moreover, an image formation approach that integrates wave number domain algorithm is presented to focus the raw data of FMCW SAR in the case of wide swath and squint mode. Point target simulation experiment demonstrates the advantages of the presented method.
The paper proposes a new method of multi-band signal reconstruction based on Orthogonal Matching Pursuit (OMP), which aims to develop a robust Ecological Sounds Recognition (ESR) system. Firstly, the OMP is employed to sparsely decompose the original signal, thus the high correlation components are retained to reconstruct in the first stage. Then, according to the frequency distribution of both foreground sound and background noise, the signal can be compensated by the residual components in the second stage. Via the two-stage reconstruction, high non-stationary noises are effectively reduced, and the reconstruction precision of foreground sound is improved. At recognition stage, we employ deep belief networks to model the composite feature sets extracted from reconstructed signal. The experimental results show that the proposed approach achieved superior recognition performance on 60 classes of ecological sounds in different environments under different Signal-to-Noise Ratio (SNR), compared with the existing method.
In this paper, a new pill-box window with arc groove disk is studied for S-band high power klystron. Its main characteristics are long pill-box and periodic grooved window disk. The long pill-box window can decrease the normal field and relieve the radio frequency loss in high power transmission, and periodic grooved window disk can suppress tangential field multipactor. The Monte Carlo (MC) method is used to build up the simulation model and analyze the increasing tendency of electrons. The simulation results indicate that long-box window with periodic arc grooved window disk can restrain multipactor effectively. Homocentric circular half-camber arc slot is put forward to overcome the disadvantages of periodic straight triangle and strait rectangular. The long pill-box with groove disk window prototype is tested in high power Travelling Wave Resonant Ring (TWRR) and the experimental results show an excellent character of this window.
The depth information of the scene indicates the distance between the object and the camera, and depth extraction is a key technology in 3D video system. The emergence of Kinect makes the high resolution depth map capturing possible. However, the depth map captured by Kinect can not be directly used due to the existing holes and noises, which needs to be repaired. We propose a texture combined inpainting algorithm in this paper. Firstly, the foreground is segmented combined with the color characteristics of the texture image to repair the foreground of the depth map. Secondly, region growing is used to determine the match region of the hole in the depth map, and to accurately position the match region according to the texture information. Then the match region is weighted to fill the hole. Finally, a Gaussian filter is used to remove the noise in the depth map. Experimental results show that the proposed method can effectively repair the holes existing in the original depth map and get an accurate and smooth depth map, which can be used to render a virtual image with good quality.
An accurate and efficient Synthetic Aperture Radar (SAR) raw data generator is of considerable value for testing system parameters and verifying imaging algorithms. Nevertheless, the existing simulator cannot exactly handle the case of the fast moving targets in high squint geometry. As for the issue, the analytical expression for the two Dimensional (2-D) signal spectrum of moving targets is derived and a fast raw echo simulation method is proposed in this study. The proposed simulator can accommodate the moving targets in the high squint geometry, whose processing steps of the simulation are given in detail and its computational complexity is analyzed. The simulation data for static and moving targets are processed and analyzed, and the results are given to validate the effectiveness of the proposed approach.
The scalability and mobility issues in current Internet architecture have drawn a lot of attentions from researchers. However, there are still many problems in current solutions. In this paper, we argue that three spaces, i.e., endpoint IDentifier(ID), Endpoint Locator(ELoc) and Routing Locator(RLoc), are necessary to realize two separations, i.e., separating identifier from locator and separating edge networks from the transit core. Following this argument, we design ID-ELoc-RLoc based architecture, i.e., IER, a separation approach to solve both mobility and scalability issues. After separating identifier from locator, mobile endpoints can ensure continuity of communications across IP address changes since their IDs do not change during moving. After separating edge networks from the transit core, the size and dynamics of global routing table would not be affected by traffic engineering, multi-homing, etc. in edge networks. In this paper, we introduce the definitions, framework, and implementation considerations of our IER architecture in details.
This paper addresses the issue of designing the detailed architectures of Field-Programmable Gate Arrays (FPGAs), which has a great impact on the overall performances of an FPGA in practice. Firstly, a novel FPGA architecture description model is proposed based on an easy-to-use file format known as YAML. This format permits the description of any detailed architecture of hard blocks and channels. Then a general algorithm of building FPGA resource graph is presented. The proposed model is scalable and capable of dealing with detailed architecture design and can be used in FPGA architecture evaluation system which is developed to enable detailed architecture design. Experimental results show that a maximum of 16.36% reduction in total wirelength and a maximum of 9.34% reduction in router effort can be obtained by making very little changes to detailed architectures, which verifies the necessity and effectiveness of the proposed model.
Topic models such as Latent Dirichlet Allocation(LDA) have been successfully applied to many text mining tasks for extracting topics embedded in corpora. However, existing topic models generally cannot discover bursty topics that experience a sudden increase during a period of time. In this paper, we propose a new topic model named Burst-LDA, which simultaneously discovers topics and reveals their burstiness through explicitly modeling each topic’s burst states with a first order Markov chain and using the chain to generate the topic proportion of documents in a Logistic Normal fashion. A Gibbs sampling algorithm is developed for the posterior inference of the proposed model. Experimental results on a news data set show our model can efficiently discover bursty topics, outperforming the state-of-the-art method.
The basic theory and principle of the artificial Controlled Source Radio MagnetoTelluric (CSRMT) method is studied and a novel CSRMT transmitter in kHz frequency band is designed. The specific circuit and measured results of some key modules in transmitter are presented, and some outdoor experimental tests have been carried out, which shows that the completed prototype of transmitter can generate a continuous sine current with frequency up to 35.33 kHz, peak-to-peak amplitude up to 40 A, and realize a reliable transmitting mode with multi-frequency and high-current. The transmitter has a wide operating band, large magnetic moment and high waveform fidelity, and can meet the requirements of shallow geological exploration with high-resolution.
Two new design approaches for constructing Low-Density Parity-Check (LDPC) codes are proposed. One is used to design regular Quasi-Cyclic LDPC (QC-LDPC) codes with girth at least 8. The other is used to design irregular LDPC codes. Both of their parity-check matrices are composed of Circulant Permutation Matrices (CPMs). When iteratively decoded with the Sum-Product Algorithm (SPA), these proposed codes exhibit good performances over the AWGN channel.
This paper presents a concurrent dual-band branch-line coupler with an independently tunable center frequency. In the proposed architecture, the quarter-wavelength lines, which work at two separated bands concurrently and can be tuned in one of them, are key components. Based on the analysis of ABCD-matrix, a novel hybrid structure and a pair of varactors topology are utilized to achieve concurrent dual-band operation and independent tunability, respectively. Using this configuration, it is convenient to tune the center frequency of the upper band, while the responses of the lower band remain unaltered. To verify the proposed idea, a demonstration is implemented and the simulated results are presented.
As a complementary technology to Binary Decision Diagram-based（BDD-based） symbolic model checking, the verification techniques on Boolean satisfiability problem have gained an increasing wide of applications over the last few decades, which brings a dramatic improvement for automatic verification. In this paper, we firstly introduce the theory about the Boolean satisfiability verification, including the description on the problem of Boolean satisfiability verification, Davis-Putnam-Logemann-Loveland（DPLL） based complete verification algorithm, and all kinds of solvers generated and the logic languages used by those solvers. Moreover, we formulate a large number optimizations of technique revolutions based on Boolean SATisfiability（SAT） and Satisfiability Modulo Theories（SMT） solving in detail, including incomplete methods such as bounded model checking, and other methods for concurrent programs model checking. Finally, we point out the major challenge pervasively in industrial practice and prospect directions for future research in the field of formal verification.
In theory, land subsidence measurement results with high accuracy can be obtained by using the Differential Interferometry Synthetic Aperture Radar（D-InSAR） at X-band. In practice, however, the measuring accuracy of D-InSAR at X-band has been seriously affected by some factors, e.g., decorrelation and high deformation gradient. In this work, the monitoring capability of D-InSAR for coal-mining subsidence is evaluated by using SAR data acquired by TerrraSAR-X system. The SAR image registration method for low coherence image pairs, the denoising phase filter for high noise level interferogram and atmospheric effects mitigation method are the key technical aspects which directly influence the measurement results of D-InSAR at X-band. Thus, a robust image registration method, an improved phase filter method and an atmospheric effects mitigation method are proposed in this paper. The proposed image registration method successfully achieves InSAR coregistration, while the amplitude cross-correlation cannot properly coregister low coherence SAR image pairs. Moreover, the time complexity of the proposed image registration method is obviously slighter than that of the Singular Value Decomposition（SVD） method. The comparing experiment results and the unwrapping phase results show that the improved Goldstein filter is more effective than the original Goldstein filter in noise elimination. The atmospheric influence correction experiment results show that the land subsidence areas with atmospheric influence correction are more clarified than that of without atmospheric influence correction. In summary, the presented methods directly improved the measurement results of D-InSAR at X-band.
By constructing a Gray map, constacyclic codes of arbitrary lengths over ring \(R = Z_{p^m } + vZ_{p^m }\) are studied, where v 2 = v The structure of constacyclic codes over R and their dual codes are obtained. A necessary and sufficient condition for a linear code to be self-dual constacyclic is given. In particular, (1+(v+1)αp)-constacyclic codes over R are classified in terms of generator polynomial, where α is a unit of \(Z_{p^m }\).
The volume of hippocampal subfields is closely related with early diagnosis of Alzheimer’s disease. Due to the anatomical complexity of hippocampal subfields, automatic segmentation merely on the content of MR images is extremely difficult. We presented a method which combines multi-atlas image segmentation with extreme learning machine based bias detection and correction technique to achieve a fully automatic segmentation of hippocampal subfields. Symmetric diffeomorphic registration driven by symmetric mutual information energy was implemented in atlas registration, which allows multi-modal image registration and accelerates execution time. An exponential function based label fusion strategy was proposed for the normalized similarity measure case in segmentation combination, which yields better combination accuracy. The test results show that this method is effective, especially for the larger subfields with an overlap of more than 80%, which is competitive with the current methods and is of potential clinical significance.
A new beam broadening synthesis technique for Synthetic Aperture Radar (SAR) antenna array, namely Projection Matrix Algorithm (PMA) is presented. The theory of PMA is introduced firstly, and then the iterative renewed manner is improved to resolve the unbalance problem under amplitude and phase control. In order to validate the algorithm correct and effective, an actual engineering application example is investigated. The beam synthesis results of 1.0∼4.5 times broadening under the phase only control and the amplitude and phase control using improved PMA are given. The results show that the beam directivity, the beam broadening, and the side-lobe level requirements were met. It is demonstrated that the improved PMA was effective and feasible for SAR application.
