The spherical harmonic series expression of electromagnetic fields excited by ELF/SLF vertical electric dipole in the spherical earth-ionosphere cavity is derived when the earth and ionosphere are regarded as non-ideal conductors. A method of speeding numerical convergence has been presented. The electromagnetic fields in the cavity are calculated by this algorithm, and the results show that the electromagnetic fields between the earth and the ionosphere are the sum of two traveling waves in the SLF band. Moreover, the results are in complete agreement with that of the well-known spherical second-order approximation in the SLF band. The electromagnetic fields in the cavity are a type of standing wave in the ELF band and the variation of the amplitude versus frequency coincides with Schumann’s resonance.

This paper proposes a semi-supervised inductive algorithm adopting a Gaussian random field (GRF) and Gaussian process. We introduce the prior based on graph regularization. This regularization term measures the p-smoothness over the graph. A new conditional probability called the extended Bernoulli model (EBM) is also proposed. EBM generalizes the logistic regression to the semi-supervised case, and especially, it can naturally represent the margin. In the training phase, a novel solution is given to the discrete regularization framework defined on the graphs. For the new test data, we present the prediction formulation, and explain how the margin model affects the classification boundary. A hyper-parameter estimation method is also developed. Experimental results show that our method is competitive with the existing semi-supervised inductive and transductive methods.

Ring signature allows specifying a set of possible signers without revealing which member actually produces the signature. This concept was first formalized in 2001 by Rivest, Shamir and Tauman. In this paper, we review the state-of-the-art of ring signature, summarize the study of ring signature schemes in the literature and investigate their relationships with other existing cryptographic schemes. We also describe a large number of extensions, modifications and applications of ring signatures after the original version of this work. Some problems in the study of this field were presented as well. Finally, we discuss a number of interesting open problems and point out the possible future work.

Rotation, scaling and translation (RST) attacks can desynchronize watermark detection, which causes failure in many watermarking systems. In this paper, an image adaptive RST invariant watermark (AWPZM) is proposed by using the rotation invariant property of pseudo-Zernike moments (PZM) and odd-even quantization. PZM of the original image is computed first, and then those suitable for watermark generation are selected. Then, magnitudes of them are odd-even quantized to generate the watermark. In detection, a normalized hamming function is employed to determine the similarity of the watermark. Experimental results show its robustness to rotation and scaling. For traditional attacks, such as JPEG compression, added noise and filtering, the similarities are all above 0.95.

Aimed at three basic services (event-driven, data query and stream query), the paper presents a QoS routing model for multimedia sensor networks. Moreover, based on the traditional ant-based algorithm, we propose an ant-based service-aware routing (ASAR) algorithm. The ASAR chooses suitable paths to meet diverse QoS requirements from different kinds of services, thus maximizing network utilization and improving network performance. Finally, extensive simulation is conducted to verify the effectiveness of our solution and we give a detailed discussion on the effects of different system parameters. Compared to the typical routing algorithm in sensor networks and the traditional ant-based algorithm, our ASAR algorithm has better convergence and significantly provides better QoS for multiple types of services in the multimedia sensor networks.

Considering the impact of aggregation cost on the performance of aggregation routes in wireless sensor networks, an aggregation-decision-based distributed routing algorithm for data aggregation is proposed. When source nodes arrive or leave, the algorithm can calculate the aggregation benefit according to data correlation, aggregation cost and transmission cost. Then the algorithm will adaptively make aggregation and routing decisions based on aggregation benefit. Therefore, it can jointly optimize the aggregation and transmission costs and reduce the energy consumption for data gathering. This distributed algorithm makes all the decisions only relying on the local information. Hence, the routing maintenance cost is limited. Simulation results show that the energy consumption difference between this distributed online algorithm and the previous offline one is within 17% under any network conditions.

Time difference of arrival (TDOA) is the positioning technique with the most potential in cellular mobile telecommunication systems. The Taylor series expansion method has been widely used in solving nonlinear equations for its high accuracy and good robustness. However, the performance of the Taylor’s method depends highly on the initial estimation. Therefore, one new algorithm, hybrid optimizing algorithm (HOA) was proposed, which combines the Taylor series expansion method with the steepest decent method. The steepest decent method features fast convergence at the initial iteration and small computation complexity. HOA takes great advantage of both methods. Simulation results show that HOA achieves better performance on positioning accuracy and efficiency.

Many recently proposed subspace clustering methods suffer from two severe problems. First, the algorithms typically scale exponentially with the data dimensionality or the subspace dimensionality of clusters. Second, the clustering results are often sensitive to input parameters. In this paper, a fast algorithm of subspace clustering using attribute clustering is proposed to overcome these limitations. This algorithm first filters out redundant attributes by computing the Gini coefficient. To evaluate the correlation of every two non-redundant attributes, the relation matrix of non-redundant attributes is constructed based on the relation function of two dimensional united Gini coefficients. After applying an overlapping clustering algorithm on the relation matrix, the candidate of all interesting subspaces is achieved. Finally, all subspace clusters can be derived by clustering on interesting subspaces. Experiments on both synthesis and real datasets show that the new algorithm not only achieves a significant gain of runtime and quality to find subspace clusters, but also is insensitive to input parameters.

To directly use a virtual surface model for action editing and movement control, a general method for creating virtual actor skeleton models and controlling movement is presented. The method includes judging borderlines of the block virtual surface model, calculating the joints, confirming the above block, and using the block hierarchical layout to create the skeleton model. Then, according to the virtual actor model and movement restriction, the study focuses on the generation of movement animation using the key frame technique and smoothing movement technique by automatically adding animation and adjusting the actor’s pose by different weights on movement amplitude. Finally, movement control of the actor in the virtual environment is implemented by real-time control and path point control, which achieve a good result.

The magnetic field distribution of an emission antenna is studied in this paper. When the slenderness ratio of the emission antenna is high, the emission antenna can be simplified as a magnetic dipole for practical application. The numerical results of the magnetic dipole magnetic field show that the magnetic magnitude distribution has a hump-shape, whose direction is perpendicular with the antenna axis direction. A localization method based on the hump-shape signal detection is presented. The experimental result shows that the precision can reach a value of ±5 cm. The method can be used to localize a pipeline robot working in a metal pipe.

The spherical harmonic series expression of electromagnetic fields excited by ELF/SLF vertical electric dipole in the spherical earth-ionosphere cavity is derived when the earth and ionosphere are regarded as non-ideal conductors. A method of speeding numerical convergence has been presented. The electromagnetic fields in the cavity are calculated by this algorithm, and the results show that the electromagnetic fields between the earth and the ionosphere are the sum of two traveling waves in the SLF band. Moreover, the results are in complete agreement with that of the well-known spherical second-order approximation in the SLF band. The electromagnetic fields in the cavity are a type of standing wave in the ELF band and the variation of the amplitude versus frequency coincides with Schumann’s resonance.

By using Mie’s theory, the boundary conditions, and some advanced mathematical knowledge, the scattering problem of a plane-wave by bi-sphere groups and of cores-traversed coherent Gauss-beams by one sphere was addressed. In each, the coefficients of the scattering-field expressions were deduced. Finally, the result was predigested and transfigured so that the available form for programming was achieved. On deducing, the former adopted the undetermined coefficient method and the latter used the plane geometry method. Moreover, the complexity of the calculation was decreased here.

Based on the brief account of the performance analysis result of the direct sequence spread spectrum (DSSS) system against a single tone continuous wave (CW) interference obtained from the traditional standard Gaussian approximation (SGA) hypothesis, the mathematical expression of the interference component of the symbol decision variable in the periodic sequence DSSS system under CW interference was deduced and the actual performance of the periodic sequence DSSS system against CW interference was researched through theoretical analysis and numerical simulations. The results indicate that the interference component of the symbol decision variable in the periodic sequence DSSS system under CW interference operates at a constant level or fluctuate monochromatically, which does not approach the standard Gaussian distribution, and the actual performance of the periodic sequence DSSS system against CW interference is completely different from the analytic result resorted to the standard Gaussian approximation (SGA). The bit error performance is correlative not only with the interference-signal ratio (ISR), the frequency offset and the phase of the CW interference sensitively, but also with the individual spread spectrum code sequence.

This article proposes a new kind of microstrip reflectarray antenna, of which the polarization could be reconfigured among all the polarization states instead of some fixed states in a dual- or multi-polarized antenna. The mechanism for polarized variability is so simple that only mechanical rotation is needed. Theoretical analysis shows that the reflected polarization covers all states and that the dual- or multi-layered unit structure sandwiched with air-gaps can broaden the bandwidth efficiently. Moreover, it is demonstrated that adopting more elements can enhance antenna gain. With these advantageous features, this kind of antenna has the potential significance for engineering applications in radar, communication, etc. In this article, a complete theoretical analysis as well as a specific design sample is given to verify this method.

One of the most critical hardware components of a ground-penetrating radar (GPR) is the antenna system. Important parameters of antennas, such as antenna bandwidth, radiation waveform and cross coupling determine the GPR system performance. The modified TEM horn antenna with distributed resistor load is presented in this paper, and the radiation properties of the antenna with the shields and absorbers are studied through the three-dimensional finite-difference time-domain (FDTD) scheme. Simulations show that the direct signal coupled from the transmitter is decreased by means of the shields and absorbers. Therefore, using the antenna in the GPR system can improve the signal-to-clutter ratio and the dynamic range of the system.

A new frequency-selective surface (FSS) with loadings is introduced in this paper and analyzed by way of period moment methods (PMMs). The simulated results show that FSS may operate in different bands and especially generate a large reduction in the resonant frequency for a fixed unit cell size through different loadings. This provides a new orientation in the development for FSS. Practical circuits are fabricated, and the measured results agree well with the simulated results.

A novel ultra low-voltage, low-power baseband-processor for UHF radio frequency identification (RFID) tag is presented here. The baseband-processor is compatible with the EPC^TM class-1 generation-2 (C1G2) UHF RFID protocol, and fits the requirements of ultra low-power of passive tags. Based on the analysis of the special power consumption of the tag, a new architecture is proposed. A novel scheme for generating pseudo-random numbers as well as a new method of partial-decoding is developed. Besides, other low-power techniques are also adopted for the special baseband-processor which implements complex functions, such as encoding/coding, anti-collision and authorization scheme, and reading/writing operation to EEPROM. The chip was fabricated in 0.35 ?m 1P3M standard CMOS process. Experimental results show that it achieves low power operation of 3.15 ?W @ 1.5 V with the core area of 1.1 mm × 0.8 mm.

The synchrotron radiation spectra of the spherical grating monochromator (SGM) working in the soft X-ray and VUV region are often contaminated by significant amounts of higher order harmonics. They cannot be suppressed completely by suitable filters. Higher order contributions in the spectral radiation standard and metrology beamline were researched using transmission grating (made in-house) and IRD AXUV100G (USA) photodiode detector. The exit beam was dispersed with the transmission grating behind the exit slit of the monochromator, and the contributions of the different orders were analyzed. The higher order distributions were quantitatively determined for three gratings with line densities of 1800, 600 and 200 l/mm. Experiment results show that in wavelengths between 5 nm and 15 nm the contributions of the higher orders to the detector signal are restricted to less than 7% even without the use of filters. In wavelength regions between 5 nm and 34 nm, the contributions of the higher orders to the detector signal are less than 14% with proper Al, Si₃N₄ and Zr filters, and after being modified by quantum efficiency of the detector, the higher order contributions are restricted to less than 6.5%. The study also shows that higher orders are almost totally suppressed by MgF₂ filter when the wavelength ranges between 115–140 nm.

In this paper, the effect of the substrate structure on the performance of the spiral inductor is investigated by the 3-D electromagnetic simulator, Ansoft high frequency structure simulator (HFSS). With variations in the substrate structure including substrate conductivity, permittivity and thickness of the dielectric layer, the performance of the inductors has been analyzed in detail. The simulation results and analyses indicate that the performance of the spiral inductor can be mostly improved by lowering the conductivity of the substrate, increasing the thickness of the dielectric layer and using the low K dielectric layer. In the mean time, some guidelines or “design rules” are summarized by the results of this study.

Ultra-shallow Si p⁺n junctions formed by plasma doping are characterized by electrochemical capacitance-voltage (ECV). By comparing ECV results with those of secondary ion mass spectroscopy (SIMS), it is found that the dopant concentration profiles in heavily-doped p⁺ layer as well as junction depths measured by ECV are in good agreement with those measured by SIMS. However, the ECV measurement of dopant concentration in the underlying lightly doped n-type substrate is significantly influenced by the upper heavily-doped layer. The ECV technique is also easy to control and reproduce. The ECV results of ultra-shallow junctions (USJ) formed by plasma doping followed by different annealing processes show that ECV is capable of reliably characterizing a Si USJ with junction depth as low as 10 nm, and dopant concentration up to 10²¹ cm^-3. Also, its depth resolution can be as fine as 1 nm. Therefore, it shows great potential in application for characterizing USJ in the sub-65 nm technology node CMOS devices.

This is our first report on the high performance 1 mm AlGaN/GaN high electron mobility transistor (HEMT) which was developed using home-made AlGaN/GaN epitaxy structures based on SiC substrate. Metal-organic chemical vapor deposition (MOCVD) was used to generate the epitaxy layers. Corresponding experiments show that the device has a gate length of 0.8 ?m exhibiting drain current density of 1.16 A/mm, transconductance of 241 ms/mm, a gate-drain breakdown voltage larger than 80 V, maximum current gain frequency of 20 GHz and maximum power gain frequency of 28 GHz. In addition, the power gain under the continues wave condition is 14.2 dB with a power density of 4.1 W/mm, while under the pulsed wave condition, power gain reaches 14.4 dB with power density at 5.2 W/mm. Furthermore, the two-port network impedance characteristics display great potential in microwave application.

Voltage distribution in windings is important for inverter-fed traction motors. The analysis on voltage distribution characteristics is significant to the study of insulation failure mechanisms and structure design. First, a distribution parameter model has been developed according to the winding structure of an inverter-fed traction motor. Based on the model, finite element differential method was employed to determine voltage distribution characteristics. Simulation results were compared with actual voltage distribution. Moreover, the influence of pulse rise time and cable was discussed. The results show that the shorter the pulse rise time is, the more uneven the voltage distribution is. In addition, cable length has little influence on voltage distribution characteristics. However, the amplitude of voltage would also increase by 40% in coils and turns.