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With large energy storage and flexible control capabilities, pulse generator is an ideal power supply for flat-top magnetic fields. However, characteristics of the pulse generator, such as nonlinearity and time variance, are a limitation on improving flat-top stability. Based on the pulse generator power supply for the flat-top magnetic field atWuhan National HighMagnetic Field Center, this paper proposes an active regulator for the flat-top magnetic field. An optimal control strategy combining selective PI control and repetitive control is proposed to restrain the circulating current between the pulse generator and the active regulator. A 50 T/140ms flat-topmagnetic field with the ripple less than 100ppm is achieved by applying an active regulator. In order to validate the effectiveness of the optimal control strategy for the high stability flat-top magnetic field with an active regulator, experimental data about the triggering angle of the rectifier are utilized in the simulation model; the result indicates that the circulating current between the pulse generator and the active regulator is suppressed to a great extent. [ABSTRACT FROM AUTHOR]

Computer-aided highly efficient electromagnetic particle-in-cell (PlC) (CHIPIC) code, developed at the University of Electronic Science and Technology of China, is a fully computer-aided code which combines modeling, calculations, and analysis with an integrated environment. CHIPIC is specifically designed for efficient modeling and simulation. CHIPIC includes a computer-aided design (CAD) system and a physical kernel. The CAD system is designed based on the common flowchart of PlC simulation to provide efficient modeling and analysis, and the physical kernel is developed to provide fast and accurate calculations. The physical kernel can run on a single processor or in parallel mode. When it runs in parallel mode, the message-pass interface and open specifications for multiprocessing are adopted. The validity of this electromagnetic PlC code is proved by simulating a magnetically insulated transmission-line-oscillator tube. [ABSTRACT FROM AUTHOR]

Current image processing and pattern recognition algorithms are not robust enough to make automated remote sensing image interpretation feasible. For this reason, we need to develop image interpretation systems that rely on human guidance. In this paper, we tackle the problem of semiautomatic road tracking in aerial photos. We propose an online learning approach that naturally integrates inputs from human experts with computational algorithms to learn road tracking. Human inputs provide the online learner with training examples to generate road predictors. An ensemble of road predictors is learned incrementally and used to automatically track roads. When novel situations are encountered, control is returned back to the human expert to initialize a new training and tracking iteration. Our approach is computationally efficient, and it can rapidly adapt to dynamic situations where the image feature distributions change. Experimental results confirm that our approach is effective and superior to existing methods. [ABSTRACT FROM AUTHOR]

A quasi-continuous high magnetic field is a special kind of pulsed magnetic field with a flat-top field longer than 100 ms. This paper proposes a hybrid power supply that consists of a capacitor power supply and a generator-rectifier power supply. A dual-coil magnet is powered to generate a 65 T/100 ms quasicontinuous high magnetic field with a ripple less than 500 ppm at the Wuhan National High Magnetic Field Center, Wuhan, China. A protection circuit consists of an R-C branch and a diode array is discussed for the worst short-circuit fault, which occurs between the first turns of inner coil and outer coil. This type of faultwill produce oscillation voltage with a high peak value and high frequency on the rectifiers. A self-adaptive PI controller with the coefficients corrected by a back propagation neural network is adopted to reduce the ripple of a flat-top. [ABSTRACT FROM AUTHOR]

High pulsedmagnetic field is becoming widely used in physics, biology, and materials. For better performance of scientific experiments, a power supply system for 100 T magnetic field is designed at Wuhan National High Magnetic Field Center. In the preliminary design, the 100 T magnet consists of three coils in a coaxial structure. Because of the multicoil system with strongcoupling structure, the current of the outer coil will drop when the middle coil is fired. And the current drop will cause adverse effects, which increase the burden of power supply and the stress ofmagnet. Based on the analysis of the mathematical model for power supply circuit, this paper proposes a modified design for power supply system, which is an auxiliary power supply connected in series with primary power supply of the outer coil for the compensation of the current drop. Corresponding parameters, circuit topology, and control strategy of capacitors are also discussed. The simulation results of the modified design of power supply system are presented in this paper. [ABSTRACT FROM AUTHOR]

Hyperspectral imagery (HSI) denoising is a challenging problem because of the difficulty in preserving both spectral and spatial structures simultaneously. In recent years, sparse coding, among many methods dedicated to the problem, has attracted much attention and showed state-of-the-art performance. Due to the low-rank property of natural images, an assumption can be made that the latent clean signal is a linear combination of a minority of basis atoms in a dictionary, while the noise component is not. Based on this assumption, denoising can be explored as a sparse signal recovery task with the support of a dictionary. In this paper, we propose to solve the HSI denoising problem by sparse nonnegative matrix factorization (SNMF), which is an integrated model that combines parts-based dictionary learning and sparse coding. The noisy image is used as the training data to learn a dictionary, and sparse coding is used to recover the image based on this dictionary. Unlike most HSI denoising approaches, which treat each band image separately, we take the joint spectral-spatial structure of HSI into account. Inspired by multitask learning, a multitask SNMF (MTSNMF) method is developed, in which bandwise denoising is linked across the spectral domain by sharing a common coefficient matrix. The intrinsic image structures are treated differently but interdependently within the spatial and spectral domains, which allows the physical properties of the image in both spatial and spectral domains to be reflected in the denoising model. The experimental results show that MTSNMF has superior performance on both synthetic and real-world data compared with several other denoising methods. [ABSTRACT FROM AUTHOR]

Object detection is an important task in very high-resolution remote sensing image analysis. Traditional detection approaches are often not sufficiently robust in dealing with the variations of targets and sometimes suffer from limited training samples. In this paper, we tackle these two problems by proposing a novel method for object detection based on structural feature description and query expansion. The feature description combines both local and global information of objects. After initial feature extraction from a query image and representative samples, these descriptors are updated through an augmentation process to better describe the object of interest. The object detection step is implemented using a ranking support vector machine (SVM), which converts the detection task to a ranking query task. The ranking SVM is first trained on a small subset of training data with samples automatically ranked based on similarities to the query image. Then, a novel query expansion method is introduced to update the initial object model by active learning with human inputs on ranking of image pairs. Once the query expansion process is completed, which is determined by measuring entropy changes, the model is then applied to the whole target data set in which objects in different classes shall be detected. We evaluate the proposed method on high-resolution satellite images and demonstrate its clear advantages over several other object detection methods. [ABSTRACT FROM PUBLISHER]

We have measured that the levitation forces relax at the different order equilibrium positions of a bulk YBaCuO su- perconductor. In a given symmetrical levitation system, high order equilibrium positions can be obtained by increasing the number of the reversal movements of the magnet; the higher order equilibrium position, the lower the relaxation of the levitation force. This method is confirmed experimentally and theoretically. For the unsymmetrical levitation system, one movement mode of the magnet and/or superconductor can reduce the relaxations of the levitation force and guidance force synchronously while the quantitiesof the levitation force and guidance force are depressed little. [ABSTRACT FROM AUTHOR]

novel method for obtaining superior intracranial focusing field in transcranial magnetic stimulation is proposed in this paper. In order to improve stimulation intensity and focalization, a semiellipse coil pair (SEP) of special coil configuration is designed and introduced. Projected onto a plane parallel to stimulating target, the two adjacent coils are in semiellipse shapes. From the front view, the SEP is bent along a symmetrical axis at specific angles. Finite-element method is adopted to analyze the relations between the geometric structure characteristics of SEP and the three-dimensional spatial distributions of the induced electromagnetic field produced by SEP. The SEP coil is compared to a conventional figure of eight coil by the positive peak value of intracranial induced electrical field and the focusing area at a target plane located 20 mm below the scalp. Results indicate that under similar power loss, the design of SEP makes it possible to enhance the positive peak value of induced electrical field and decrease the focusing area simultaneously. A real human head modeled as homogeneous and isotropic is occupied in this paper to verify our method. [ABSTRACT FROM AUTHOR]

High-stability flat-top pulsed magnetic field can meet severe demands of field intensity and stability in modern scientific experiments. The higher stability of the flat-top magnetic field would be of more benefit to the observation of experimental phenomena (such as specific heat measurement andNMRexperiment). In order to reduce the ripple of the flat-top magnetic field, an active ripple compensator is presented in this paper for the 50-T dual-coil magnet system at the Wuhan National High Magnetic Field Center. The active ripple compensator has the advantages of modularization, flexibility, and low energy consumption. The simulation model including the generator-rectifier power supply is established on the MATLAB/Simulink platform. The ripple of a 50-T magnetic field has been reduced from 1500 to 60 ppm, which verifies the feasibility of the scheme. [ABSTRACT FROM AUTHOR]

This paper proposes a new method of risk assessment for lightning shielding flashover in transmission lines. This is used to improve the performance of lightning shielding failure which is a frequently serious problem. The method can be efficiently implemented in the optimization of a 3-D model. Three-dimensional laser scanning is used to derive the analytical 3-D model to high precision. This includes the data of the whole span line's structure and terrain parameters. In this study, the evaluation of lightning shielding flashover risk of each tower is calculated using the whole span calculation method associated with the laser scanning data and the given parameters of lightning activities. The evaluation results for the Gechen line in the zone near the Three Gorges area are presented based on the proposed method. Using a comparison of theoretical values and actual statistical data, this paper concludes that the proposed new method has better performance than the traditional method. [ABSTRACT FROM PUBLISHER]

In the merged multimedia packet-switched networks, the limited or no end-to-end Quality of Service(QoS) guarantees induce that rate control has been evolved to joint source-channel adjustment architecture based on application-oriented QoS. Based on the statistical analysis under the spatial intra and temporal inter prediction subject to a universal spatial-temporal coding framework and a general error concealment by the decoder, an end-to-end distortion estimation model is proposed. On the basis of the analytic model, this paper fulfills a picture quality parameters selection solution with rate-distortion (R-D) Lagrange optimization for a general coding engine including H.264/AVC, exploiting either the source-driven iterative prediction or feedback recursion. Further, a corresponding joint source-channel rate control strategy is proposed. For the real-time variable bit-rate (VBR) video transmission under a given time-varying network condition, the strategy could estimate an instantaneous available transmission rate on traffic smoothing and codec's butter control, adopt the proposed an end-to-end distortion regressive model and a global optimal error control parameters selection, and address the consistent bit allocation in group of picture (GOP) level, picture level, and MB level. The extensive network simulation experiments show a better and more consistent end-Wend picture quality, in contrast with the locally optimal control strategy at MB level. [ABSTRACT FROM AUTHOR]

This paper addresses the implementation architecture and protocol procedure of the dedicated broadband access network TV transmission system. According to application-oriented quality of service (QoS), two alternative rate control schemes for multiple DTV programs transmission are proposed collaborating with MPEG-2 system strategy and IP-base network multiplexing mechanism. As to the network bandwidth utilization, a flexible RTP-based synchronization resilience scheme for VBR transport stream (TS) transmission is realized to ensure the performance requirement for MPEG-2 standard As to the MPEG-2 system strategy, moreover, a parallel VBR transcoding/encoding rate control algorithm for CBR TS transmission could achieve a consistent picture quality for multiple DTV programs under a constrained fixed-rate network bandwidth. For adapting the variable access network bandwidth, the system main control module can flexibly schedule the available rate control scheme for multiple slave service multiplexers. Experimental results demonstrate that the proposed schemes not only improve the traditional TV broadcast adaptation to Internet, but also achieve a more ideal program picture quality constrained by multi-program parallel multiplexing. [ABSTRACT FROM AUTHOR]

In this paper, an end-to-end rate-distortion (R-D) estimation recursive model is proposed, on the basis of the statistical analysis of the spatial and temporal prediction as well as a general error concealment method by the video decoder. It takes the source quantization error, channel error, and the subsequent error spatial-temporal propagation into account. Then a corresponding integrated error resilience scheme, which adopts a global optimal intra-macro block (MB) refreshment ratio and visual acuity selection procedure, is introduced. Moreover, it employs a combined source-channel bit allocation strategy, which could estimate an instantaneous available source transmission rate under a given time-varying network condition. The network experiments show that this scheme is effective and applicable for a better and more consistent picture quality in the receiver end. [ABSTRACT FROM AUTHOR]