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Support vector machine (SVM) is regarded as one of the most effective techniques for supervised learning, while the Gaussian kernel SVM is widely utilized due to its excellent performance capabilit...

In order to constantly improve the output characteristics of wind turbines, the HIL (Hardware In the Loop) experimental platform of wind turbines is built to optimize control. According to the product parameters of 1.5 MW direct-drive PMSG (Permanent Magnet Synchronous wind Generator) of Dongfang Electric Corporation (DEC), the simulation model of wind turbine is built in RTDS (Real Time Digital Simulator), and optimised by comparing with the wind speed–power curve of products, the simulation model of wind turbine with engineering accuracy can be obtained. Base on the engineering model and actual controller of products, the HIL experimental platform of wind turbines is built to optimise control. In the case of unbalanced or asymmetrical grid voltage, in order to make the wind turbine output be stable, the DDSOGI-PLL (direct Decoupling Double Second-Order Generalized Integral Phase-Locked Loop) is proposed to improve the performance of PLL, the active/reactive current decoupling algorithm based on positive and negative sequence voltage orientation respectively is proposed to eliminate the negative sequence current to maintain a constant output power. The effectiveness of algorithm is verified by the HIL experimental platform, the active power output of wind turbine remains constant, the grid-connected adaptability of wind turbines is improved significantly.

In order to explore the operation and maintenance characteristics of important auxiliary machines in large-scale power plant coal-fired boilers, a running state assessment model for auxiliary equipment is established. In this paper, taking the complex variability of the operating conditions of thermal power equipment into consider, auto encoder model combined with fuzzy synthetic is proposed. Based on the residual of the model results and the actual power plant operation data, combined with the fuzzy evaluation model to establish a state assessment model, and analyze the actual situation of the induced draft fan of the power plant, to make a real-time assessment of operation status. The evaluation results show the advantages of the state assessment strategy proposed in this paper, and it can reflect the deterioration of the induced draft fan status in time, providing guidance for the operation and maintenance of the equipment.

In recent years, with the increase of information processing capacity of optical networks and the continuous improvement of high-density optical communication technology, the requirements for the performance of light sources are also increased. High-quality VCSEL with beam polarization stability control plays an increasingly important role in the above fields. The combination of liquid crystal and vertical cavity surface emitting laser (VCSEL) array can realize wavelength tunability and precise polarization control. At the same time, the introduction of liquid crystal will also change the thermal characteristics of VCSEL array. In this paper, the structure of VCSEL array is designed and the experimental research on the thermal characteristics of VCSEL array is carried out. The effects of nematic liquid crystal layer on the thermal characteristics of VCSEL array are compared and analyzed. The experimental results show that the threshold current temperature change rate of 1 × 1, 2 × 2 and 3 × 3 surface liquid crystal VCSEL array can be reduced by 23.6% and the thermal resistance can be reduced by 26.75%. Moreover, the saturated optical power of VCSEL array can be improved to a different degree. Meanwhile, the liquid crystal layer can effectively increase the heat transverse conduction and reduce the optical hole. The temperature difference between the light outlet and the table makes the heat conduction time very short at a small distance between the light outlet and the table, which is more conducive to the uniform temperature distribution of the laser array. The experimental results show that the temperature difference between the light outlet and the surrounding is less than 0.5 ℃. To sum up, the introduction of liquid crystal layer into VCSEL array not only greatly accelerates the thermal diffusion of laser array unit, but also reduces the junction temperature of active region, improves the thermal characteristics of VCSELs laser array, and lays a good theoretical and experimental foundation for realizing the high beam quality single polarization wavelength controllable VCSEL laser array.

LBG algorithm is commonly used in multidimensional signal processing. It's one of the most effective methods to generate codebooks. Better initial codebook of LBG algorithm leads to better quality of final codebook. In order to find one effective method to design LBG initial codebook, four design methods of initial codebook for LBG algorithm are compared, including Random method, Splitting method, Most-Dispersed Code words Initialization (MDCI) and Greedy Tree Growing Algorithm (GTGA). The codebooks after LBG algorithm are used to quantize Line Spectral Frequency (LSF) coefficients in speech coding. Simulation by C programming language demonstrates that GTGA is optimal. Because it executes within a sShort span of HtimeH, and both the number of iteration times and run time are close to by splitting method in LBG algorithm. Moreover MSE is minor and Average Spectral Distortion is small.

In this paper, we introduce an orthogonalization aided distributed scheduling algorithm for multiuser MIMO broadcast channels (MU-MIMO BC). In this algorithm each mobile station (MS) selects transmission scheme, including beamforming (BF) and spatial multiplexing (SM) according to its channel state and feeds back channel state information (CSI) adaptively. On receiving CSI from each MS, the base station (BS) activates user subset and an orthogonalization based precoding scheme is applied to eliminate co-channel interference (CCI). The proposed user scheduling algorithm is carried out by MSs and BS corporately. The system feedback load depends on each MS's channel quality. Compared with existing methods, the proposed scheme can achieve high system capacity as well as better BER performance.

The reconstruction of dense cloud points is the key technique in reverse engineering and is the bottleneck in the progress of reverse engineering. Based on analyzing the current classic methods deeply, this paper presents a new method to reconstruct NURBS surface according to triangle meshes. This method combines the vividness of Bezier surface reconstruction with the accuracy of NURBS surface reconstruction and makes complicated dense points reconstruction accurately and effectively. In this paper, it devises a reconstruction module FastForm based on the method discussed in paper and builds a reverse engineering system regarding the IGES format as data interface. Finally, the actual effect of this reverse engineering system is verified by an instance.

A new multiple access protocol for wireless Internet access called user-dependant perfect-scheduling multiple access (UPMA) is proposed. Packet transmissions are scheduled according to the number of active users, packet queue length and round-robin service rule. The number of active users are determined by the proposed self-organizing algorithm. Users in the ad hoc network are divided into clusters by the self-organizing algorithm. UPMA algorithms for star and ad hoc wireless networks are given. Performance analysis shows that UPMA has very high throughput.

An effective scheme for reducing the peak-to-average power ratio (PAPR) of a multicarrier signal is presented. By adding one or more artificial signals, the envelope of the composite signal can be restricted within a predefined range. The algorithm is derived and the results of computer simulation are given. The results show that the algorithm achieves good performance and is applicable for different kinds of multicarrier signals.

Multicarrier direct sequence code-division multiple access (MC-DS-CDMA) has been adopted as one of the proposals in IMT-2000. A main disadvantage of multicarrier modulation is that it exhibits a high peak-to-average power ratio (PAPR). This paper investigates the effects of amplitude clipping on multicarrier DS-CDMA signals. It is shown that considerable reductions of PAPR are possible at the expense of limited inband spectral distortion and out-of-band clip noise emissions. The amount of inband distortion can be explained as signal-to-noise ratio (SNR). With PAPR decreasing, SNR abates. A trade-off point is chosen.

In this paper we present the enhanced X-ray Timing and Polarimetry mission - eXTP. eXTP is a space science mission designed to study fundamental physics under extreme conditions of density, gravity and magnetism. The mission aims at determining the equation of state of matter at supra-nuclear density, measuring effects of QED, and understanding the dynamics of matter in strong-field gravity. In addition to investigating fundamental physics, eXTP will be a very powerful observatory for astrophysics that will provide observations of unprecedented quality on a variety of galactic and extragalactic objects. In particular, its wide field monitoring capabilities will be highly instrumental to detect the electro-magnetic counterparts of gravitational wave sources. The paper provides a detailed description of: (1) the technological and technical aspects, and the expected performance of the instruments of the scientific payload; (2) the elements and functions of the mission, from the spacecraft to the ground segment., Accepted for publication on Sci. China Phys. Mech. Astron. (2019)