非正常凸多面体及凹多面体的落地概率

通过研究非正常凸、凹多边形板着地后的特点,得出了非正常凸多边形板及凹多边形板各边着地的概率.进而用立体角的概念,在分析非正常凸、凹多面体着地的特点后,得到了非正常凸多面体及凹多面体各面着地的概率.     

Structure buckling hybrid reliability analysis of a supercavitating projectile using a model with truncated probability and multi-ellipsoid convex set uncertainties

Structure buckling problems for supercavitating projectiles are often observed in high underwater velocity operating conditions. As a result, it is necessary to perform a structure buckling reliability analysis. It is common that \hboxprobabilistic and nonprobabilistic uncertainty information exist simultaneously. Also, it is reasonable that probability distributions of most random variables in engineering are treated as truncated probability distributions. In this paper, a new hybrid model is proposed, which deals with structure performance function with both truncated probability distribution variables and multi-ellipsoid convex set variables. The model discussed here is adapted for two separate cases in the standard super-sphere space, i.e., limit state surface interferences with a unit super-sphere region or not. The hybrid reliability index is calculated using a modified limit step length iteration algorithm to ensure convergence. Good convergence and validity of the iteration algorithm are verified using numerical examples with highly nonlinear structure performance function. The hybrid model is applied to the structure buckling hybrid reliability analysis of a supercavitating projectile. Results show that structure buckling hybrid reliability index increases with the increase in the ratio of base diameter to cavitator diameter, and decreases with the increase of initial launch velocity. Also, uncertainty degree of cavitator drag coefficient and initial launch velocity should be controlled in demonstration for high structure buckling reliability of supercavitating projectiles.     

江苏弶港JC-1203钻孔沉积物粒度特征及其古环境意义

选取江苏弶港地区JC-1203钻孔, 通过分析其岩性、沉积物粒度参数和概率累计曲线, 结合已有文献资料和测年数据, 将JC-1203钻孔0~50.00m段自上而下分为5个沉积单元(DU1、DU2、DU3、DU4和DU5). 研究表明: DU1段(0~4.00m), 中值粒径(Md)为3.40~4.94Φ, 平均4.31Φ, 分选系数(δ1)为0.94~1.82, 平均1.24, 粒度概率累积曲线由跃移?–悬浮两组分构成, 滚动组分缺失, 反映了MIS1末期研究区为潮坪相沉积环境; DU2段(4.00~27.39m), Md为1.96~4.87Φ, 均值3.30Φ, δ1为0.54~2.17, 均值1.25, 曲线形态为跃移?–悬浮两单元构成, 反映研究区MIS1中?–末期为潮流沙脊相沉积; DU3段(27.39~37.33m), Md为1.90~4.18Φ, 均值2.79Φ, δ1为0.54~2.24, 均值1.34, 曲线形态为跃移?–悬浮两单元构成, 反映研究区MIS1早?–中期为滨海相沉积环境; DU4段(37.33~45.54m), Md为4.14~6.79Φ, 均值6.00Φ, δ1为1.5~2.3, 均值1.8, 概率累积曲线形态复杂多变, 反映研究区MIS3中?–末期的陆相河流沉积环境; DU5段(45.54~ 50.00m), Md为3.18~6.40Φ, 均值4.94Φ, δ1为0.99~1.97, 均值1.67, 曲线形态以滚动?–跃移?–悬浮三单元构成为主, 反映研究区MIS3早期的浅海相沉积环境.     

The inelastic electron tunneling spectroscopy of edge-modified graphene nanoribbon-based molecular devices

The inelastic electron tunneling spectroscopy(IETS) of four edge-modified finite-size grapheme nanoribbon(GNR)-based molecular devices has been studied by using the density functional theory and Green's function method. The effects of atomic structures and connection types on inelastic transport properties of the junctions have been studied. The IETS is sensitive to the electrode connection types and modification types. Comparing with the pure hydrogen edge passivation systems, we conclude that the IETS for the lower energy region increases obviously when using donor–acceptor functional groups as the edge modification types of the central scattering area. When using donor–acceptor as the electrode connection groups, the intensity of IETS increases several orders of magnitude than that of the pure ones. The effects of temperature on the inelastic electron tunneling spectroscopy also have been discussed. The IETS curves show significant fine structures at lower temperatures. With the increasing of temperature, peak broadening covers many fine structures of the IETS curves.The changes of IETS in the low-frequency region are caused by the introduction of the donor–acceptor groups and the population distribution of thermal particles. The effect of Fermi distribution on the tunneling current is persistent.     

On the reverse leakage current of Schottky contacts on free-standing GaN at high reverse biases

In this work, a dislocation-related tunneling leakage current model is developed to explain the temperature-dependent reverse current–voltage(I–V –T) characteristics of a Schottky barrier diode fabricated on free-standing GaN substrate for reverse-bias voltages up to-150 V. The model suggests that the reverse leakage current is dominated by the direct tunneling of electrons from Schottky contact metal into a continuum of states associated with conductive dislocations in GaN epilayer.A reverse leakage current ideality factor, which originates from the scattering effect at metal/GaN interface, is introduced into the model. Good agreement between the experimental data and the simulated I–V curves is obtained.     

Transition from tunneling regime to local point contact realized on Ba_(0.6)K_(0.4)Fe_2As_2 surface

Using scanning tunneling spectroscopy, we studied the transition from tunneling regime to local point contact on the iron-based superconductor Ba_(0.6)K_(0.4)Fe_2As_2. By gradually reducing the junction resistance, a series of spectra were obtained with the characteristics evolving from single-particle tunneling into Andreev reflection. The spectra can be well fitted to the modified Blonder–Tinkham–Klapwijk(BTK) model and exhibit significant changes of both spectral broadening and orbital selection due to the formation of point contact. The spatial resolution of the point contact was estimated to be several nanometers, providing a unique way to study the inhomogeneity of unconventional superconductors on such a scale.     

Total ionizing radiation-induced read bit-errors in toggle magnetoresistive random-access memory devices

The 1-Mb and 4-Mb commercial toggle magnetoresistive random-access memories(MRAMs) with 0.13 μm and 0.18-μm complementary metal–oxide–semiconductor(CMOS) process respectively and different magnetic tunneling junctions(MTJs) are irradiated with a Cobalt-60 gamma source. The electrical functions of devices during the irradiation and the room temperature annealing behavior are measured. Electrical failures are observed until the dose accumulates to 120-krad(Si) in 4-Mb MRAM while the 1-Mb MRAM keeps normal. Thus, the 0.13-μm process circuit exhibits better radiation tolerance than the 0.18-μm process circuit. However, a small quantity of read bit-errors randomly occurs only in 1-Mb MRAM during the irradiation while their electrical function is normal. It indicates that the store states of MTJ may be influenced by gamma radiation, although the electrical transport and magnetic properties are inherently immune to the radiation. We propose that the magnetic Compton scattering in the interaction of gamma ray with magnetic free layer may be the origin of the read bit-errors. Our results are useful for MRAM toward space application.     

α decay properties of ~(297)Og within the two-potential approach

The α decay half-life of the unknown nucleus ~(297)Og is predicted within the two-potential approach, andα preformation probabilities of 64 odd-A nuclei in the region of proton numbers 82 Z 126 and neutron numbers 152 N 184, from ~(251)Cf to ~(295)Og, are extracted. In addition, based on the latest experimental data, a new set of parameters for α preformation probabilities considering the shell effect and proton-neutron interaction are obtained.The predicted α decay half-life of ~(297)Og is 0.16 ms within a factor of 4.97. The predicted spin and parity of the ground states for ~(269)Sg,~(285)Fl and ~(293)Lv are 3/2~+, 3/2~+ and 5/2~+, respectively.     

Cooperative spectrum sensing based on a modified shuffled frog leaping algorithm in 5G network

The explosion of different types of wireless communications is leading to an impending spectrum famine. As a result, spectrum sensing has gained increasing interest from governments, industry and regulators. In this paper, a novel approach for cooperative spectrum sensing is proposed based on a modified shuffled frog leaping algorithm (SFLA). This approach is to fuse the perceived results of multiple nodes, and to improve the detection reliability. Simulations are used to compare the performance of the modified SFLA to the conventional one. The performance of the proposed cooperative spectrum sensing method based on the modified SFLA and that of the cooperative spectrum sensing method using modified deflection coefficient (MDC) are also compared. Results show that the proposed SFLA outperforms the traditional SFLA, and the proposed cooperative spectrum sensing method based on the modified SFLA gives higher miss detection probability than the MDC-based method, which validates the effectiveness of the modified SFLA-based cooperative sensing method.