Search

Copyright of Systems Engineering & Electronics is the property of Journal of Systems Engineering & Electronics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Beijing University of Technology is the property of Journal of Beijing University of Technology, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The non-coincidence of the positive and negative charge centers of perovskite ferroelectric crystals leads to spontaneous polarization inside the materials to generate a built-in electric field. The existence of built-in electric field is beneficial to the transmission and separation of photo-excited carriers. However, perovskite ferroelectric materials are mostly wide-band gap semiconductors. Photogenerated electrons and holes generated when materials are excited are easy to recombine. Therefore, adjusting their photoelectrochemical performance has become a research hotspot. In this paper, the principles and progress of controlling the photoelectrochemical performance of perovskite ferroelectric materials are introduced, such as doping and substitution of elements, deposition of precious metals on the surface, construction of semiconductor heterostructure and multi-mechanism coupling. The applications status of these materials in photocatalytic degradation of pollutants, photocatalytic hydrogen production and photoelectrochemical water splitting hydrogen production in recent years are emphatically introduced. [ABSTRACT FROM AUTHOR]

Hydrogen energy is a clean，high energy，environmentally friendly resource and considered as one of the most promising candidates for replacing fossil fuels in the future. In this work，3D Ni foam (NF) was etched by hydrofluoric acid (HF)，followed by phosphorization in tube furnace to obtain an integrated electrode (Ni2P/E-NF). The relative surface area of Ni2P/E-NF is almost 2.8 times as high as that of NF. The designed Ni2 P/E-NF as a binder-free integrated electrode displays enhanced catalytic activity of hydrogen production with a low onset overpotential of about 27 mV. For driving a cathodic current density of 10 mA/cm2，it only needs an overpotential of 63 mV. The negligible difference in the polarization curves from before and after 4 000 CV cycles indicates that the Ni2 P/E-NF has excellent electrochemical stability. Such excellent performance of Ni2 P/ENF could be ascribed to the rich surface area and exposed active sites to be utilized during the HER. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to investigate the terminating load voltage of the unshielded multi-core cable coupled with lightning electromagnetic pulse(LEMP), we simulate LEMP within the bounded-wave transmission line which is input with a lightning surge signal produced by WU-800-type MARX generator and conduct the relevant experiments towards multi-core cable lines radiated by LEMP. We can get the respond laws of induced voltage of the load by changing the length of unshielded multi-core cable, angles between LEMP and cable, waveforms of LEMP as well as cable terminal loads including linear and non-linear loads. Results show that the amplitude of induced voltage is mainly determined by rising part of electromagnetic field waveforms and the pulse width has little effect on the induced voltage. The respond amplitude and the respond frequency are obviously affected by the length of cable. The polarization direction of the electric field has a great impact on the amplitude of terminal response, but it does not change the waveforms of the induced voltage. With the termination of test side increasing, the induced voltage is gradually increased, but the load in the other side has no effect on the induced voltage. [ABSTRACT FROM AUTHOR]

For millimeter wave (MMW) radar system of dual polarization, this paper presents a polarization identification method of active jamming decoys. Firstly, the principle of dual polarization technique is introduced, and the characteristics of dual polarization echo of the representative radar targets and various active decoys are analyzed in detail. Secondly, some effective characteristics of active decoys and radar targets are obtained to express their polarization characteristics differences, such as polarization ratio and polarization undulation. Thirdly, an identification method based on self - adaptive constant false alarm rate (CFAR) threshold is proposed. Finally, a dual polarization test radar system is constructed to gather and analyze the experimentation echo data of buildings, vertical polarization, horizontal polarization and left-handed circular polarization active decoys, and the experimentation results prove that the dual polarization identification method of active decoys is feasible and effective. [ABSTRACT FROM AUTHOR]

In order to obtain a stable beam pattern and further improve the performance of adaptive beamforming for polarization sensitive array, a Quaternion-Amplitude and Phase Estimation (Q-APES) algorithm is presented for polarization- space adaptive filtering in the paper. First, the quaternion signal model is given and the inherent orthogonal structure of the two component signal output of each sensor has been kept well by using the quaternion signal model. It is obvious that the quaternion signal model is more suitable for two component vector sensor array signal processing than the conventional long vector signal model which is based on the complex number. Second, the conventional APES algorithm for spatial domain filtering has been expanded to the polarization-space adaptive beamforming. The proposed Q-APES algorithm is derived theoretically and the quaternion optimal weight vector is obtained following. Finally, computer simulation results are shown to verify the correctness of the proposed algorithm. The results indicate that Q-APES algorithm can achieve a better filtering performance than the existing Q-MVDR algorithm under the circumstances of strong desired signal power or low sampling snapshot numbers. Moreover, Q-APES algorithm can also perform well even if the incident interference signals are fully correlated with the desired signal. [ABSTRACT FROM AUTHOR]

According to the various formats cause the phenomenon of audio file's watermarking embedding becomes complex and complicated, this paper used FFMPEG to make the various formats transform into a unity format to embed the watermarking which improved the efficiency and result, it selected improved quantizing discrete cosine transform algorithm to embed the watermarking. First, it converted the binary image into the one dimensional sequence and modulated the sequence with scrambling encryption and polarization operation, then performed the digital audio signal the quantizing DCT transform, according to each different subparagraphs energy grade, it used different embedding strength and selected four different levels coefficients, repeated embedding. In the experimental simulation results, there doesn' t exist obvious differences between the transformed audio signal and the original audio signal, the watermark algorithm is imperceptible to digital audio signal such as Gauss white noise interfere, low pass filter and loss compression. [ABSTRACT FROM AUTHOR]

A direction-of-arrival (DOA) estimation algorithm for un-correlatively distributed (UD) sources is proposed, based on electromagnetic vector-sensor array(EMVSA). An UD sources model with electromagnetic vector-sensor array (EMVSA-UD) is established, which has considered both space and polarization distribution. The estimator could exploit approximately orthogonal property between pseudo signal and pseudo noise subspaces. Moreover, the proposed algorithm does not require to decompose the eigenvalue of sample covariance matrix and to estimate effective dimension of the pseudo signal subspace. Simulation results indicate that the EMVSA-UD is reasonable, and DOA estimation algorithm performs well. [ABSTRACT FROM AUTHOR]

To solve the problem of target polarization loss and phase distortation of conventional three-dimension polarization filter for High Frequency Surface Wave Radar (HFSWR), a three-dimension polarization filter approach based on oblique projection is proposed in this paper. The spatial polarization parameters of the target signal and interference signal are used to span the corresponding subspace respectively, and then an oblique projection operator is obtained to form a polarization filter vector. Compared with the conventional three dimensions polarization filter, no amplitude loss and phase distortion of the target signals are introduced while the interference is mitigated perfectly, the improvement of significant signal to interference plus noise power ratio (SINR) can be expected and the phase coherence of the target signal can be kept. The simulation results indicate that the proposed method can effectively suppress the polarized interference for HFSWR. [ABSTRACT FROM AUTHOR]

In order to simplify the separation of radar echo and deception and to get the Jones vector of deception, a simple and convenient method to extract radar deception is proposed. By transmitting a group of relative polarization agile signals, the scattered wave and deception can be separated during the calculation of the signal output by the receiver, while utilizing the polarization effect of the target and the constant polarization state of deception. Compared with existing interference feature extraction algorithms, resources can be saved when this algorithm is implemented in single chip. The simulation results show that the relative errors of the calculation are less than 10% , when INR is more than 11.8 dB. [ABSTRACT FROM AUTHOR]

PURPOSE: To investigate the effects of TiN and TiCN coating on corrosion resistance of pure titanium in the simulated oral environment. METHODS: The dental pure titanium commonly used in making removable denture was casted with 15 specimens, 10mmxl0mmxlmm in size. The specimens were randomly divided into group A, group B and group C. In the group B and group C, the specimens were coated with a thickness of 2.5p.m TiN and TiCN coating on surface by multi-arc physical vapor deposition, respectively. After microscopic energy spectrum analysis, microstructure and phase diffraction were examined by FESEM. Hardness and Young modulus of the various coating were determined by nanoindentation. The polarization curves of all specimens in artificial saliva were measured by PARSTAT'2273 electrochemical station. The data were analyzed with SPSS 17.0 software package for t test, one-way ANOVA and nonparametric test. RESULTS: Both the mierohardness and elastic modulus in the group B and group C were significantly superior to those in the group A (P<0.001). Meanwhile, both the microhardness and elastic modulus in the group C were significantly higher than those in the group B (P<0.01). Corrosion potential (Ecorr) was group A > group B > group C (P< 0.05). However, corrosion current density (Icorr) was significantly lower in the group A than in the group B, and in the group A than in the group C (P<0.01), while not significantly different between the B and group C (P>0.05).Breakdown potential (Ecorr) was group A

The eigen values of linear polarized mode (U,W) are calculated based on the eigen value equations of linear polarized mode of multimode fiber. The situation of power distribution of different modes is obtained when put the results into the power distributing function of fiber. With the use of fiber coupling equation, the coupling coefficient of every mode is calculated. The coupling efficiency and length of coupling fiber are calculated in different conditions. Depending on the analysis of numerical value, how to improve the efficiency of multimode fiber coupling is summarized. The result reflects that, for manufacturing the fiber coupler or combiner, it is necessary to consider the relation between fiber parameters and length of coupling fiber to achieve the optimal coupling. [ABSTRACT FROM AUTHOR]

Present simulation method for micro-Doppler characteristics or approximate method of scattering computation is generally based on point-target model and its research result by these methods is hardly suitable for extended targets. For this reason, a simulation approach based on a powerful full-wave numerical method, hybrid FE-BI-MLFMA, is presented in this paper. By taking blunt nosed cone target as an example, micro-Doppler characteristics of a conducting cone target and a head-coated cone target, under different types of micro-motions and polarizations, are investigated in this paper. The conclusion is that, though the intensity of micro-Doppler track is changed with polarization direction and coating structure, the form of micro-Doppler track is invariant. This research can provide quantitative reference support for recognition and identification of ballistic missile warhead and decoy. [ABSTRACT FROM AUTHOR]

The development of a Ka-band monopulse variable polarization antenna is presented, based on polarization synthesis theory. This kind of microstrip array antenna consists of several linearly polarized subarrays of rotational symmetry, and change the polarization mode by adjusting the phase of each subarray. The circular polarization of three subarrays and four subarrays has high polarization purity with over 30 dB cross-polarization and less than 3 dB axial ratio within the half power beamwidth; and the imbalance of two peaks in difference beam is less than 1 dB, and null depth is over 30 dB. [ABSTRACT FROM AUTHOR]

The spacer conformations of two main-chain liquid crystals (LCs), CNφφOCH2CH2-X-CH2CH2O-φφCN, (X = O; CBE2, X CH2; CBA5), have been investigated on the basis of conformational energies derived from density functional calculations and the orientational order parameters from ²H NMR experiments under the rotational isomeric state approximation. Polarization microscopic and differential calorimetric observations revealed that CBA5 and CBE2 form an enantiotropic and a monotropic nematic LC phase, respectively. The intramolecular orientational correlation P2(cos ψ) of CBA5 was found to remain invariant over the entire range of the LC phase, whereas P2(cos ψ) of CBE2 definitely decreases with decreasing temperature. Here, ψ stands for the angle between mesogenic core and molecular axis. These results suggest that LC molecules will show the so-called nematic conformation to adapt themselves to the uniaxial potential field, and that the stability of nematic conformation attributed to the bond rotational characteristic of chain segment (CO-C-C-X) strongly correlates with the stability of the nematic LC phase. [ABSTRACT FROM AUTHOR]