Semi-Empirical Formulas for Nuclear Charge Radii

Considering the relationship between the nuclear radius and the average bindingenergy of nucleons,a simple semi-empirical formula for the nuclear rms charge radii is suggest-ed together with the formula for light neutron-rich nuclear rms neutron radii.These formulascan well fit the new experimental values.

轻核区中子晕结构的系统研究

在相对论连续谱Hartree-Bogoliubov(RCHB)理论框架下,采用非线性核子-核子有效相互作用NL-LN参数组系统计算了从锂到镁(3≤Z≤12)同位素原子核的基态性质,包括中子、质子和物质均方根半径以及密度分布.计算结果不仅再现了中子晕候选核11Li,11Be,14Be和17B中的中子晕现象,而且还预言了13Be,14,15B,31F,23,24O和31,32,34Ne也存在中子晕.

Effect of Signal Filtering on Image Quality of Projection-Based Magnetic Particle Imaging

Purpose: Magnetic particle imaging (MPI) allows for imaging of the spatial distribution of magnetic nanoparticles (MNPs) in positive contrast, with high sensitivity, high spatial resolution, and high imaging speed. It is necessary to increase the signal-to-noise ratio to enhance the reliability of MPI. The purpose of this study was to investigate the effect of signal filtering on the image quality and quantitativity in projection-based MPI using phantoms. Materials and Methods: We fabricated two kinds of phantom (cylindrical tube phantom with a diameter of 6 mm and A-shaped phantom) and evaluated the effect of signal filtering in terms of root-mean-square (RMS) granularity and the correlation coefficient between iron concentrations of MNPs and average MPI values for four filter modes (THRU, BPF, BEF, and LPF). In the THRU mode, the signal input was output without passing through the filter. In the BPF mode, only the third-harmonic signal was passed using a band-pass filter (central frequency: 1200 Hz, band width: 1/3 octave). In the BEF mode, the first-harmonic signal was eliminated using a band-elimination filter (central frequency: 400 Hz, band width: 1/3 octave). In the LPF mode, only the signal with a frequency less than the third-harmonic frequency was passed using a low-pass filter (cut-off frequency: 1200 Hz, -24 ± 2 dB/octave). The RMS granularity was obtained by calculating standard deviations of the pixel values in the MPI image without MNPs, whereas average MPI values were obtained by drawing a circular region of interest with a diameter of 6 mm on the MPI image of the cylindrical tube phantom. Results: When using the filtered back-projection (FBP) method with a ramp filter for image reconstruction, the RMS granularity and correlation coefficient decreased in the order of THRU, BPF, BEF, and LPF. In the BPF mode, however, some artifacts were observed. When using the maximum likelihood-expectation maximization (ML-EM) algorithm with an iteration number of 15, the correlation coefficient decreased in the order of THRU, BPF, BEF, and LPF, whereas the RMS granularity did not largely depend on the filter mode and was significantly (p Conclusion: The BEF mode is adequate for the FBP method in projection-based MPI, whereas THRU is a best option in use of the ML-EM algorithm.

Predictions of nuclear charge radii

In this study,we improve the relations of the charge-radius difference of two isotopes by considering a term that relates to the proton number and the parity of the neutron number.The correction reduces the root-mean-squared deviation to 0.0041 fm for 651 nuclei with a neutron number larger than 20,in comparison with experiment-al data compiled in the CR2013 database.The improved relations are combined with local relations consisting of the charge radii of four neighboring nuclei.These combinations also prove to be efficient in describing and predicting nuclear charge radii and can reflect the structure evolutions of nuclei.Our predictions of 2467 unknown nuclear charge radii at competitive accuracy,which are calculated using these two types of relations,are tabulated in the Supplemental Material.

应用原子核的宏观－微观模型研究远离稳定线核的性质

应用原子核的宏观－微观模型研究远离稳定线核的性质，得到了一些结果，例如质子和中子滴线，质子和中子密度分布及其均方根半径和中子皮厚度随同位素位移的变化．对一些奇异核性质的计算结果同相对论平均场方法计算的结果作了比较，对质子滴线附近核的质子放射性也作了简要讨论．

Geologic-seismic models,prediction of shallow-water lacustrine delta sandbody and hydrocarbon potential in the Late Miocene,Huanghekou Sag,Bohai Bay Basin,northern China

The Huanghekou Sag is located at the southeast part of the Bohai Bay Basin, northern China. Large-scale shallow lake delta developed in the Neogene provided suitable geological conditions for the formation of a subtle oil-gas reservoir in this area. The key for analyzing sandstone reservoir and sedimentary facies is by using seismic attributes(amplitude) to establish the relationship between lithology combination and seismic attributes. The lower unit of Late Miocene Minghuazhen Formation at the BZ34 block in the Huanghekou Sag was subdivided into 10 parasequence sets(PSS). Thicker sandstones mainly occurred in PSS1 and PSS10, whereas thin sandstones are mostly observed within other parasequence sets. This study presents statistics and analyses of lithology, i.e., statistics of root-meansquare(RMS) amplitude and lithology of well locations in different parasequence sets of the study area,as well as 1-D forward seismic models of 7 types of lithology combinations, the establishment of a spatial distribution of 2-D sandbody, forward seismic models etc. Our study indicates that high amplitude peaks correspond to thicker sandbodies, while low amplitude indicates non-development of sandbodies(generally less than 2 m), and medium amplitude agrees well with large sets of mudstones interbedded with medium and thinner sandstones. Different sand-mudstone combinations genetically reflect a combination of multiple micro-facies, therefore, amplitude features can predict sandbodies as well as facies characteristics.

Two-body and three-body halo nuclei

We have extracted the nuclear asymptotic normalization coefficients (ANC) for the virtual transitions B→A+N via some transfer reactions and the radioactive nuclear beam experiments. With these coefficients, root-mean-square (rms) radii for the valence particle in some possible halo nuclei have been calculated. The values of rms radii extracted with ANC approach are nearly model-independent, hence are a good quantity for the investigation of nuclear halo. In addition, we have also calculated the rms radii for the two valence neutrons in some three-body systems in terms of the relationship between the radii of valence particle, core nucleus and nuclear matter. With two conditions for nuclear halo formation, we have examined these extracted rms radii. The results show that 11Be(1/2+, g.s), 12B(1-, 2.621 MeV), 13C(1/2+, 3.089 MeV), 14C(0-, 6.903 MeV), 14C(1-, 6.094 MeV), 15C(1/2+, g.s) and 19C(1/2+, g.s) with the valence particle in the 2s ground or excited state are the neutron halo nuclei, whereas 17F(1/2+, 0.495 MeV) and 21Na(1/2+, 2.423 MeV) are the proton halo nuclei in the excited state. For three-body systems, except the well-established two-neutron halo nuclei 6He and 11Li, 14Be and 17B might be the two-neutron halo nuclei as well.

Phasor-domain Dynamic Model of Asymmetric Current Injection Controller for Converter-interfaced Generator

This paper presents a controller model of asymmetric current injection for converter-interfaced generators suitable for root-mean-square(RMS)phasor-domain,fundamentalfrequency,three-phase,and dynamic simulation tools.The effectiveness of the proposed controller is assessed with simulations in test systems with high percentage of converter-interfaced generation.The simulations focus on the operation of protection relays that use negative-sequence quantities in their directional elements.This paper also presents and compares two strategies to limit reactive negative-sequence currents,and active and reactive positive-sequence currents.A tutorial test system and a regional system part of the actual Brazilian Interconnected Power System are used to assess the correctness of the proposed controller in three-phase fundamental-frequency RMS dynamic simulations.