Calculation of microscopic nuclear level densities based on covariant density functional theory

In this study,a microscopic method for calculating the nuclear level density(NLD)based on the covariant density functional theory(CDFT)is developed.The particle-hole state density is calculated by a combinatorial method using single-particle level schemes obtained from the CDFT,and the level densities are then obtained by considering collective effects such as vibration and rotation.Our results are compared with those of other NLD models,including phenomenological,microstatisti-cal and nonrelativistic Hartree–Fock–Bogoliubov combinatorial models.This comparison suggests that the general trends among these models are essentially the same,except for some deviations among the different NLD models.In addition,the NLDs obtained using the CDFT combinatorial method with normalization are compared with experimental data,including the observed cumulative number of levels at low excitation energies and the measured NLDs.The CDFT combinatorial method yields results that are in reasonable agreement with the existing experimental data.

Model Selection in Estimation of Covariance Functions for Growth of Angora Goats

Covariance functions have been proposed as an alternative to model longitudinal data in animal breeding because of their various merits in comparison to the classical analytical methods.In practical estimation,different models and polynomial orders fitted can influence the estimates of covariance functions and thus genetic parameters.The objective of this study was to select model for estimation of covariance functions for body weights of Angora goats at 7 time points.Covariance functions were estimated by fitting 6 random regression models with birth year,birth month,sex,age of dam,birth type,and relative birth date as fixed effects.Random effects involved were direct and maternal additive genetic,and animal and maternal permanent environmental effects with different orders of fit.Selection of model and orders of fit were carried out by likelihood ratio test and 4 types of information criteria.The results showed that model with 6 orders of polynomial fit for direct additive genetic and animal permanent environmental effects and 4 and 5 orders for maternal genetic and permanent environmental effects,respectively,were preferable for estimation of covariance functions.Models with and without maternal effects influenced the estimates of covariance functions greatly.Maternal permanent environmental effect does not explain the variation of all permanent environments,well suggesting different sources of permanent environmental effects also has large influence on covariance function estimates.

Tilted Axis Rotation of ^(57)Mn in Covariant Density Functional Theory

The self-consistent tilted axis cranking covariant density functional theory based on the point-coupling interaction is applied to investigate the tilted axis rotation in ^57 Mn. The observed data for band C are reproduced well with the assigned configuration eonfig 1. The shears mechanism for magnetic rotation is examined by investigating microscopically the orientation of angular momentum and the corresponding contributions. It is found that config 1 and config 3 correspond to a rotation of high-K character. Config 2 corresponds to a rotation of magnetic character. However, due to the presence of electromagnetic transition B（M1） and B（E2）, collective rotation plays an essential role in the competition with magnetic rotation.

基于二次分数低阶协方差的时延估计方法

针对强脉冲噪声背景下基于分数低阶统计量时延估计方法性能退化且需要噪声先验知识的问题,提出了一种基于二次分数低阶协方差的时延估计新方法。所提方法首先利用有界非线性Sigmoid函数对含有脉冲噪声的信号进行预处理,使其在不影响有用信号时延信息的基础上对附加脉冲噪声进行充分压缩;然后对处理后的收发信号进行二次分数低阶协方差运算,即求得发射信号的自分数低阶协方差和收发信号的互分数低阶协方差之后,再次计算二者的互分数低阶协方差,以期更大程度上抑制脉冲噪声的影响。通过模拟仿真实验对所提方法进行了有效性验证,结果表明所提方法突破了分数低阶矩阶次需小于Alpha稳定分布噪声特征指数的限制,并且比分数低阶协方差方法具有更高的估计精度。仿真实验结果表明在广义信噪比-10 dB情况下,时延估计用时为0.0560 s,准确率达到97.76%。

协方差分析描述函数法的通用化数值算法

协方差分析描述函数法(covariance analysis describing function technique,CADET)在处理系统的随机响应问题上具有求解迅速、仿真精度高等优点.但对于复杂系统,其理论推导过程、求解系统解析响应方程较为复杂繁琐.为进一步推广CADET的应用,依托高斯–埃尔米特积分法,提出了一种通用化的CADET数值算法.作为算法验证,以车辆行驶过程中的随机振动为例,建立了几种不同非线性悬架车辆的二自由度动力学模型,并将CADET通用化数值算法与传统CADET算法及蒙特卡罗法进行了对比分析.仿真结果表明,CADET的通用化数值算法可以达到满足应用要求的计算精度,这验证了所提数值算法的有效性,且具有更强的泛化应用于复杂非线性动力系统的价值.

不同微生境毛尖紫萼藓形态结构性状差异性与协变特征

【目的】毛尖紫萼藓(Grimmia pilifera)是典型的石生耐旱藓类,广布于我国南北各省,其生长往往受到干旱和贫瘠生长环境的限制,是自然界的拓荒者之一。研究不同微生境中毛尖紫萼藓形态结构性状的差异性与协变特征,为开展藓类植物耐旱机理研究及深入揭示石生耐旱藓类在不同微环境的适应机制提供基础数据。【方法】以3种不同遮荫程度微生境(竹林开放式遮蔽岩石S_(1)、向阳裸岩E、薜荔完全遮蔽岩石S_(2))下的毛尖紫萼藓为研究对象,通过测定15个形态结构性状,即7个单株性状(中部叶片夹角、中部叶长度、中部毛尖长度、上部毛尖长度、植株高度、带毛尖的植株宽度、不带毛尖的植株宽度)和8个茎叶微结构性状(茎横截面长、茎横截面宽、茎中部细胞长、茎中部细胞宽、茎细胞密度、叶中肋宽、叶细胞长、叶细胞宽),计算各性状的变异系数,探究其形态结构性状在不同微生境间的差异性与协变特征。【结果】在单株性状中,株高、植株宽度、植株宽度(带毛尖)、叶片夹角和中部叶长最大值均出现在S_(1)生境,最小值多出现在E生境,而中部毛尖长为S_(2)>E>S_(1)。无论何种微生境,毛尖长度的变异性均较高。在茎叶微结构性状中,茎细胞长、叶细胞长及叶细胞宽均表现为S_(1)生境显著高于E生境,其他5个茎叶微结构性状在3个微生境间无显著差异(P>0.05)。叶细胞在S_(1)生境中最大,S_(2)生境中次之,E生境中最小。所有性状均属于中等以下程度变异,具有一定的可塑性。主成分分析表明,不同微生境下毛尖紫萼藓15个性状间的协变特征不完全一致,且呈现较明显的分异特征,其中S_(1)生境的毛尖紫萼藓综合生长性能相对较好。【结论】在3种不同微生境下,毛尖紫萼藓形态结构性状所反映的生长性能表现为:S_(1)>S_(2)>E。毛尖紫萼藓功能性状间具有一定的协变趋势,但出现了微生境间的差异化,这是对不同微环境长期响应和适应的结果。该研究结果可为进一步探讨藓类植物这类特殊植物类群对不同微生境的响应与适应提供理论依据。

A Cautionary Note on the Application of GIS in Spatial Optimization Modeling

Spatial optimization as part of spatial modeling has been facilitated significantly by integration with GIS techniques. However, for certain research topics, applying standard GIS techniques may create problems which require attention. This paper serves as a cautionary note to demonstrate two problems associated with applying GIS in spatial optimization, using a capacitated p-median facility location optimization problem as an example. The first problem involves errors in interpolating spatial variations of travel costs from using kriging, a common set of techniques for raster files. The second problem is inaccuracy in routing performed on a graph directly created from polyline shapefiles, a common vector file type. While revealing these problems, the paper also suggests remedies. Specifically, interpolation errors can be eliminated by using agent-based spatial modeling while the inaccuracy in routing can be improved through altering the graph topology by splitting the long edges of the shapefile. These issues suggest the need for caution in applying GIS in spatial optimization study.

基于航迹概率假设密度的多传感器多目标跟踪

针对基于概率假设密度(probability hypothesis density,PHD)的分布式多传感器多目标跟踪(distributed multi-sensor multi-target tracking,DMMT)存在无法形成航迹、计算复杂度高、目标漏检等问题。本文基于航迹PHD后验估计提出了一种DMMT方法。为此,首先构建了各节点估计航迹间相似性度量矩阵,并采用匈牙利算法实现最优航迹匹配;其次采用协方差逆准则对关联航迹实现并行融合;最后基于概率生成泛函推导了一种鲁棒的DMMT方法。仿真实验验证了所提算法在目标状态估计精度、计算有效性和实时性方面的优势。

均值函数相等检验及在高频股指收益率中应用

针对具有相依特征的函数型数据样本,提出利用经典的Newey-West估计式对它们的长期协方差函数进行估计,从而可以得到更加准确的函数主成分,进而对独立同分布条件下的均值函数相等检验统计量进行改进,并通过模特卡罗模拟和实例分析与现有独立同分布和相依条件下的检验方法进行比较。模特卡罗模拟结果表明,相比于现有检验方法,文中所提改进方法的检验水平与显著性水平更接近,而检验功效更高。实例分析结果表明,2018年沪深300和上证180股指1分钟和5分钟累积收益率的均值函数相等,即这两个金融市场的投资收益水平相当。

Karhunen-Loeve展开在Abaqus中的实现

基于数值分析理论,提出一种Karhunen-Loeve展开的数值算法,采用Python和Fortran混合编码的方式将其内嵌至Abaqus的计算内核中,分析程序编制的关键要素并开展误差分析。结果表明:编制的程序可行,随机场展开合理,数值算法精度较高,特征值、特征函数以及协方差函数的计算结果与理论解一致。

Robustness of the octupole collectivity in 144Ba within the cranking covariant density functional theory in 3D lattice

The octupole deformation and collectivity in octupole double-magic nucleus 144Ba are investigated using the Cranking covariant density functional theory in a three-dimensional lattice space.The reduced B(E3)transition probability is implemented for the first time in semiclassical approximation based on the microscopically calculated electric octupole moments.The available data,including the I-ωrelation and electric transitional probabilities B(E2)and B(E3)are well reproduced.Furthermore,it is shown that the ground state of 144Ba exhibits axial octupole and quadrupole deformations that persist up to high spins(I≈24h).

基于时空协方差函数的风能场景生成方法与应用

与传统发电不同,风力发电具有较大的随机性与时空相关性.在风力发电并网的电力系统优化调度问题中,保障电力调度在不同风力发电功率场景中的最优执行是决策问题的关键点,因此高质量的风能场景生成非常重要.基于高斯随机过程和时空协方差函数表征风力发电站输出功率的时空相关性,由Pair Copula模型建立联合概率分布,通过经验概率逆变换方法实现具体场景.评估生成场景的多种指标,验证生成场景的优越性.基于修改的IEEE 6总线系统建立电力系统机组组合的混合整数规划模型,求解不同场景下的问题,验证场景生成方法在风力发电并网调度问题中所具有的经济性和可行性.

轻度认知功能障碍大脑网络的结构共变分析

目的探讨轻度认知功能障碍(mild cognitive impairment,MCI)与健康对照(healthy control,HC)两组间脑网络皮质体积结构共变是否存在差异,以及脑网络皮质体积与认知功能的相关性。方法对21例MCI患者和34名HC使用剑桥自动化成套神经心理测试(the Cambridge neuropsychological test automated battery,CANTAB)进行认知功能评估。对被试进行颅脑结构像扫描,运用CAT12软件提取17个脑网络皮质体积,并基于脑网络皮质体积的相关性构建脑网络结构共变。结果协方差分析控制年龄、性别、受教育年限,MCI组CANTAB中单次选择反应时间(F=4.944,P=0.031,未校正)以及6格间隔错误数(F=4.075,P=0.049,未校正)高于HC组。MCI组的17个脑网络皮质体积均值小于HC组,但差异无统计学意义(P>0.05)。置换检验结果显示,MCI组在边缘系统子网络B(Lim⁃bic B network)和颞顶网络(TempPar network)这2个脑网络皮质体积间的结构共变要弱于HC组(P=0.018,FWE校正)。偏相关分析发现,MCI组和HC组CANTAB测试分数与Limbic B和TempPar这2个脑网络的皮质体积均无统计学相关(P>0.05,FDR校正)。结论MCI患者在Limbic B和TempPar这2个脑网络皮质体积间的结构共变减弱,但认知功能与这2个脑网络的皮质体积缺乏相关性。

Three-dimensional potential energy surface for fission of^(236)U within covariant density functional theory

We calculate the three-dimensional potential energy surface(PES)for the fission of the compound nucleus^(236)U using covariant density functional theory with constraints on the axial quadrupole and octupole deformations(β_(2),β_(3))coexistence of the elongated and compact fission modes is predicted for comes shallow across a large range of quadrupole and octupole deformations for small scission line in the(β_(2),β_(3))plane extends to a shallow band,leading to fluctuations of several to ten MeV in the estimated total kinetic energies and of several to approximately ten nucleons in the fragment masses.

基于最小二乘配置的陌生海域海底地形反演方法

针对目前在无船测水深数据支撑的陌生海域海底地形模型构建困难的现状,提出了可将船测水深数据和重力数据已知海区协方差函数统计结果迁移、推广并应用于与已知数据海区重力异常相似的船测水深数据空白的陌生海区,运用最小二乘配置方法实现陌生海域海底地形模型构建。首先在西太平洋某1°×1°数据已知海区,依据最小二乘配置方法构建了相应的海底地形模型(BAT_LSC_1)。模型评估结果表明,BAT_LSC_1模型与导纳函数构建的海底地形模型检核精度相当,检核相对精度优于4%。海区重力异常作灰度化处理后,应用影像粗匹配和精匹配技术搜寻出与已知海区重力异常特征相似区域,迁移已知海区协方差统计结果应用于陌生海区,运用最小二乘配置方法构建陌生海区海底地形模型(BAT_LSC_2)。试验检核结果表明,BAT_LSC_2整体表现优于ETOPO1模型和应用导纳函数构建的海底地形模型,验证了本文方法思路的可行性和适用性。

基于STSS模型的改进及其应用

随着信息技术的迅猛发展和大数据时代的到来,一些时空数据集不仅规模庞大,还包含着各种不同的信息变量,因此需要合适的表达来描述这类时空数据的特征。在French等提出的STSS模型的基础上,引入协变量函数和周期函数对响应变量的影响。利用STSS模型关于基函数和惩罚函数的运用,对大规模数据做平滑处理,同时还伴随着协变量以及周期性对观察变量的影响,这样的结合使得改进的模型能更全面、更贴合实际地描述时空数据的结构和变化。最后使用模拟数据和真实时空数据验证了该方法的优越性和适用性。

正则化方法对连续协变量项目功能差异的检测及其应用

提出检测连续协变量条件下项目功能差异的正则化方法,并将其与Logistic回归方法进行比较。模拟数据分析结果表明:1)在所有条件下,正则化方法的一类错误率比Logistic回归方法低。在DIF项目比例为20%时,正则化方法的检测效果优于Logistic回归方法。2)正则化方法对0.3的DIF值不敏感,检验力低。3)两种方法的一类错误率随着样本量增加、DIF值增加而增加,检验力随着样本量增加、DIF值增加、DIF项目比例减小而增加。将正则化方法应用于PISA2012数学测验数据,进行连续协变量下的DIF检测及正则化方法的实际应用,结果也发现正则化方法相比于Logistic方法可以更好地控制一类错误率。

基于均值未知的高维协方差矩阵的估计

给出了一种基于均值未知情形下,高维协方差矩阵估计的新算法。即当矩阵的维数p大于样本容量n时,根据随机矩阵理论,通过样本协方差矩阵特征值的边缘密度函数和总体特征值的对数似然函数,得到目标矩阵特征值的估计量。基于收缩估计的思想,对目标矩阵特征值和样本协方差矩阵特征值进行收缩估计,通过特征值的估计得到高维协方差矩阵的一个新的估计量。数值模拟表明,对于多元正态的总体,高维协方差矩阵的新估计量较样本协方差矩阵的精度更好。

Level density of odd-A nuclei at saddle point

Based on the covariant density functional theory,by employing the core–quasiparticle coupling(CQC)model,the nuclear level density of odd-A nuclei at the saddle point is achieved.The total level density is calculated via the convolution of the intrinsic level density and the collective level density.The intrinsic level densities are obtained in the finite-temperature covariant density functional theory,which takes into account the nuclear deformation and pairing self-consistently.For saddle points on the free energy surface in the(β_(2),γ)plane,the entropy and the associated intrinsic level density are compared with those of the global minima.By introducing a quasiparticle to the two neighboring even–even core nuclei,whose properties are determined by the five-dimensional collective Hamiltonian model,the collective levels of the odd-A nuclei are obtained via the CQC model.The total level densities of the^(234-240)U agree well with the available experimental data and Hilaire’s result.Furthermore,the ratio of the total level densities at the saddle points to those at the global minima and the ratio of the total level densities to the intrinsic level densities are discussed separately.

Strangeness S=-2 baryon-baryon interactions and femtoscopic correlation functions in covariant chiral effective field theory

We study the baryon-baryon interactions with strangeness S=-2 and corresponding momentum correlation functions in leading order covariant chiral effective field theory.The relevant low energy constants are determined by fitting to the latest HAL QCD simulations,taking into account all the coupled channels.Extrapolating the so-obtained strong interactions to the physical point and considering both quantum statistical effects and the Coulomb interaction,we calculate the ΛΛ and Ξ^(-)p correlation functions with a spherical Gaussian source and compare them with recent experimental data.We find a good agreement between our predictions and the experimental measurements by using the source radius determined in proton-proton correlations,which demonstrates the consistency between theory,experiment,and lattice QCD simulations.Moreover,we predict the Σ^(+)Σ^(+),Σ^(+)Λ,and Σ^(+)Σ^(-) interactions and corresponding momentum correlation functions.We further investigate the influence of the source shape and size of the hadron pair on the correlation functions studied and show that the current data are not very sensitive to the source shape.Future experimental measurements of the predicted momentum correlation functions will provide a non-trivial test of not only SU(3) flavor symmetry and its breaking but also the baryon-baryon interactions derived in covariant chiral effective field theory.