China Institute of Electronics

The 26Mg 27Al reaction, as part of the Mg-Al cycle, is closely related to the abundance ratio of 26Al to 27Al in stars. It also has a direct connection to the Mg-Al anti-correlation observed in globular clusters (GCs). Its reaction rate is determined by multiple known and unknown low-energy resonances. In this work, we measured the angular distributions of the proton transfer reaction 26Mg(7Li, 6He)27Al populating three levels at excitation energies from 8.324 MeV to 8.597 MeV using the HI-13 tandem accelerator and a high-precision magnetic spectrograph. Proton spectroscopic factors were extracted from the angular distributions corresponding to these three states, and the resonance strengths contributing to the reaction rate were updated. At the same time, the latest calculated reaction rate shows that the result for the 52.8 keV resonance significantly increases the total reaction rate at .

The analytic solution of sparse signal reconstruction algorithm based on L1 regularization is a biased estimation, which leads to the underestimation of target intensity when applied to sparse SAR imaging, resulting in the bias effect and affecting the reconstruction accuracy. In this paper, we quantitatively analyze the bias effect in SAR imaging applications, and analyse the influence of target intensity, signal-to-noise ratio, intensity ratio of adjacent targets in the observation scene on the reconstruction bias. In order to suppress the bias effect and improve the reconstruction accuracy, we adopt a class of algorithms based on nonconvex penalty, and verify the performance of these algorithms using simulations and real data.

In this paper, a microwave photonic dual band radar based on a photonic-assisted de-chirp processing receiver is proposed. The dual band operation is realized independently and simultaneously with a single set of hardware. At a transmitter end, two linear frequency-modulated signals separately located in C-band and Ku-band are transmitted, echoes are collected and sent to a receiver to implement photonic-assisted de-chirp processing. At the receiver end, a main modulator with a special structure, which consists of four parallel sub-modulators, is employed. The echoes and reference signals of C-band and Ku-band are applied to two pairs of sub-modulators of the main modulator, which are biased at the peak points for C-band and biased at the null points for Ku-band. In this case, the intermediate frequency signals of C-band and Ku-band produced by de-chirp processing locate at two different frequencies. Thus operation in different bands based on a unified system is achieved. An experiment operating in C-band and Ku-band with a bandwidth of 700 MHz and 3600 MHz is conducted. The results verify the concept of the dual band radar and show the potential of photonic technology to improve the performance of modern radar system.

Ships on synthetic aperture radar (SAR) images will be severely defocused and their energy will disperse into numerous resolution cells under long SAR integration time. Therefore, the image intensity of ships is weak and sometimes even overwhelmed by sea clutter on SAR image. Consequently, it is hard to detect the ships from SAR intensity images. A ship detection method based on local region power spectrum of SAR complex image is proposed. Although the energies of the ships are dispersed on SAR intensity images, their spectral energies are rather concentrated or will cause the power spectra of local areas of SAR images to deviate from that of sea surface background. Therefore, the key idea of the proposed method is to detect ships via the power spectra distortion of local areas of SAR images. The local region power spectrum of a moving target on SAR image is analyzed and the way to obtain the detection threshold through the probability density function (pdf) of the power spectrum is illustrated. Numerical P- and L-band airborne SAR ocean data are utilized and the detection results are also illustrated. Results show that the proposed method can well detect the unfocused ships, with a detection rate of 93.6% and a false-alarm rate of 8.6%. Moreover, by comparing with some other algorithms, it indicates that the proposed method performs better under long SAR integration time. Finally, the applicability of the proposed method and the way of parameters selection are also discussed.

Polarimetric synthetic aperture radar (PolSAR) obtains polarimetric scattering of targets. The scattering properties are usually considered as invariant in azimuth. In some new SAR mode, such as wide-angle SAR and circular SAR (CSAR), targets are illuminated for longer time and look angle changes a lot. Moreover some targets have different physical shape in different look angle. Thus scattering properties can no longer be considered as invariant in azimuth. Variations across azimuth should be considered as useful information and are important parts of targets’ scattering properties. In this paper, polarimetric data are cut into subapertures in order to achieve scattering properties in different look angle. Target vector and coherency matrix are de- fined for multi-aperture situation. Polarimetric entropy for multi-aperture situation is then defined and named with multi-aperture poalrimetric entropy(MAPE). MAPE is calculated based on eigenvalue of multi-aperture coherency matrix. MAPE describes variations of scattering properties across subapertures. When MAPE is low, scattering properties change a lot across subapertures, which refers to anisotropic targets. When MAPE is high, there are few variations across subapertures, which refers to isotropic targets. Thus anisotropic targets and isotropic targets can be identified by MAPE. The effectiveness of MAPE is demonstrated on polarimetric CSAR(Pol-CSAR) data, acquired by the Institute of Electronics airborne CSAR system at P-band.

A theoretical model based on common pump structure is proposed to analyze the laser output characteristics of DPAL (Diode pumped alkali vapor laser) and XPAL (Exciplex pumped alkali laser) in this paper. The model predicts that an optical-to-optical efficiency approaching 80% can be achieved for continuous-wave four- and five-XPAL systems with broadband pumping which is several times of pumped linewidth for DPAL. Operation parameters including pumped intensity, temperature, cell’ s length, mixed gas concentration, pumped linewidth and output mirror reflectivity are analyzed for DPAL and XPAL systems basing on the kinetic model. The result shows a better performance in Cs-Ar XPAL laser with requirements of relatively high Ar concentration, high pumped intensity and high temperature. Comparatively, for Cs-DPAL laser, lower temperature and lower pumped intensity should be acquired. In addition, the predictions of selection principal of temperature and cell’s length are also presented. The conception of the equivalent “alkali areal density” is proposed in this paper. It is defined as the product of the alkali density and cell’s length. The result shows that the output characteristics of DPAL (or XPAL) system with the same alkali areal density but different temperatures turn out to be equal. It is the areal density that reflects the potential of DPAL or XPAL systems directly. A more detailed analysis of similar influences of cavity parameters with the same areal density is also presented. The detailed results of continuous-wave DPAL and XPAL performances as a function of pumped laser linewidth and mixed gas pressure are presented along with an analysis of influences of output coupler.

This manuscript describes an airborne SAL system for remote targets imaging. We have recently completed an experiment of ISAL at 1.1 km outdoor using the system. Relative motion was provided by a rotating platform with three cubes on while the SAL system kept stationary. System, signal collection, processing and the results are described in the paper. The result showed that the system had the ability to image for moving targets. Accurate rotating platform and complex target will be used to achieve further ISAL experiments on the next stage.

Layer-by-layer self-assembly ultrathin films continue to be of significant interest among researchers for its broad application in diverse areas. Based on electrostatic attraction between materials with opposite charges, multilayer films of (PSS/Cyt c) ₆, (GNPs/Cyt c) ₅ and (PDDA/DNA) ₆ had been successfully fabricated on the surface of gold chip, respectively. The adsorption process had been followed by in suit spectral surface plasmon resonance (SPR) technique in real time. The experimental results demonstrate that adsorption of materials onto the gold chip can induce a redshift of resonance wavelength and the amount of adsorption can be determined by the change of resonance wavelength. Kinetics studies suggest that adsorption of cytochrome c (Cyt c) or deoxy ribonucleic acid (DNA) obeys Langmuir-isotherm theory, while adsorption of gold nanoparticles (GNPs) obey diffusion-controlled model. These results also indicate that GNPs need more time to reach adsorption equilibrium than Cyt c and DNA, due to a small value of diffusion coefficient.0 increasing with the layer, however, (GNPs/Cyt c) ₅ and (PDDA/DNA) ₆ show a nonlinearly increase. Moreover, through controlling the number of assembled layer, the thickness of multilayer films can be precise designed.