非线性滞后型微分方程非局部边值问题的正解

By using Krasnoselskii‘s fixed-point theorem on a suitable cone, several existence results and corresponding properties of positive solutions of nonlocal boundary value problem for nonlinear retarded differential equation are obtained.     

广义耦合KdV孤子方程的达布变换及其偶孤子解

根据广义耦合KdV孤子方程的Lax对, 借助谱问题的规范变换, 一个包含多参数的达布变换被构造出来. 利用达布变换来产生广义耦合KdV孤子方程的偶孤子解, 并且用行列式的形式来表达广义耦合KdV孤子方程的偶孤子解. 作为应用, 广义耦合KdV孤子方程的偶孤子解的前两个例子被给出.     

资金利率和通货膨胀率下双复合POISSON风险模型

本文将双复合POISSON风险模型推广到保费随机收取的新模型并考虑了资金利率和通货膨胀率,运用鞅分析方法获得了其破产概率所满足的Lundberg不等式及其一般表达式。     

A class of coupled nonlinear Schrödinger equations: Painlevé property,exact solutions,and application to atmospheric gravity waves

The Painleve integrability and exact solutions to a coupled nonlinear Schrodinger （CNLS） equation applied in atmospheric dynamics are discussed. Some parametric restrictions of the CNLS equation are given to pass the Painleve test. Twenty periodic cnoidal wave solutions are obtained by applying the rational expansions of fundamental Jacobi elliptic functions. The exact solutions to the CNLS equation are used to explain the generation and propagation of atmospheric gravity waves.     

Structural,electronic,and magnetic properties of vanadium atom-adsorbed MoSe_2 monolayer

Using the first-principles calculations, we study the structural, electronic, and magnetic properties of vanadium adsorbed MoSe_2 monolayer, and the magnetic couplings between the V adatoms at different adsorption concentrations. The calculations show that the V atom is chemically adsorbed on the MoSe_2 monolayer and prefers the location on the top of an Mo atom surrounded by three nearest-neighbor Se atoms. The interatomic electron transfer from the V to the nearestneighbor Se results in the polarized covalent bond with weak covalency, associated with the hybridizations of V with Se and Mo. The V adatom induces local impurity states in the middle of the band gap of pristine MoSe_2, and the peak of density of states right below the Fermi energy is associated with the V- dz~2 orbital. A single V adatom induces a magnetic moment of 5 μBthat mainly distributes on the V-3d and Mo-4d orbitals. The V adatom is in high-spin state, and its local magnetic moment is associated with the mid-gap impurity states that are mainly from the V-3d orbitals. In addition,the crystal field squashes a part of the V-4s electrons into the V-3d orbitals, which enhances the local magnetic moment.The magnetic ground states at different adsorption concentrations are calculated by generalized gradient approximations(GGA) and GGA+U with enhanced electron localization. In addition, the exchange integrals between the nearest-neighbor V adatoms at different adsorption concentrations are calculated by fitting the first-principle total energies of ferromagnetic(FM) and antiferromagnetic(AFM) states to the Heisenberg model. The calculations with GGA show that there is a transition from ferromagnetic to antiferromagnetic ground state with increasing the distance between the V adatoms. We propose an exchange mechanism based on the on-site exchange on Mo and the hybridization between Mo and V, to explain the strong ferromagnetic coupling at a short distance between the V adatoms. However, the ferromagnetic exchange mechanism is sensitive to both the increased inter-adatom distance at low concentration and the enhanced electron localization by GGA+U, which leads to antiferromagnetic ground state, where the antiferromagnetic superexchange is dominant.     

属性约简在中医证候诊疗数据分析中的应用

针对中医诊疗数据和诊疗结果数据存在不确定性等特点,通过研究基于粗糙集的属性约简方法,引入属性作用集差异度概念,并定义基于属性作用集差异度的属性重要度的计算方法,提出基于属性作用集差异度的属性约简算法,并将其应用于中医证候数据约简中以实现中医证候诊疗症状关键因子提取的需要。通过实际中医证候诊疗数据集上测试及与其他属性约简算法的测试比较,结果表明所提出的属性约简算法是有效的。     

1,8-萘酰亚胺衍生物的设计、合成及其对半胱氨酸的识别研究

巯基氨基酸水平异常与多种疾病相关,其检测仍存在一定的局限,研究检测巯基氨基酸的荧光探针具有一定的价值.以苊为原料合成了61个1,8-萘酰亚胺衍生物,研究了该类化合物的荧光性能及其作为半胱氨酸含量测定的荧光探针的可能性.紫外光谱分析表明1,8-萘酰亚胺衍生物上N-取代基对最大吸收波长无明显影响;荧光光谱(FL)的性能测试显示硝基萘酰亚胺衍生物N-甲基-4-硝基-1,8-萘二甲酰亚胺(4a)～4-硝基-N-间氟苯基-1,8-萘二甲酰亚胺(4s)无荧光,氨基萘酰亚胺衍生物N-甲基-4-氨基-1,8-萘二甲酰亚胺(5a)～4-氨基-N-间氟苯基-1,8-萘二甲酰亚胺(5s)有强烈黄色荧光,而马来酰亚胺萘酰亚胺衍生物N-甲基-4-(1H-吡咯-2,5-二酮-1-基)-1,8-萘二甲酰亚胺(6a)～4-(1H-吡咯-2,5-二酮-1-基)-N-(间氟苯基)-1,8-萘二甲酰亚胺(6s)有微弱蓝色荧光,其中7个马来酰亚胺萘酰亚胺衍生物探针对半胱氨酸(Cys)溶液有荧光点亮效应.对7个探针加入21种其它氨基酸作为干扰项的测试显示探针对半胱氨酸检测有良好的选择性.研究了不同pH值下荧光强度,检测探针与半...     

有关复合材料迭层板平面响应的理论

为了准确地分析迭层板的平面响应，本文建立了一种以Ｒｅｉｓｓｎｅｒ的新的混合变分原理为基础的迭层板剪切变形理论。将一阶剪切变形理论的平面位移叠加一项交错线性数函数平模拟平面位移沿厚度的变化，为保证层间应力的连续性，将横向剪切应力处理成厚度从标的二次函数。将该理论具体实施到迭层的柱形弯曲问题中，理论解与Ｐａｇａｎｏ的精确解比较的结果说明了本文的迭层板理论对于分析平面响应是非常有效的。     

具有恐惧效应、时滞和扩散的随机捕食-食饵模型的动力学分析

研究了一类具有恐惧效应、时滞及空间扩散的随机捕食-食饵系统.首先,证明系统在任意正初值下有唯一存在的全局正解;其次,通过构造适当的Lyapunov函数,结合伊藤公式和切比雪夫不等式,证明系统的解是随机最终有界的;最后,利用随机微分方程比较定理,分别得到了种群灭绝与平均持续生存的充分条件.     

高效液相色谱法同时测定复杂食品基质中8种合成色素的含量北大核心CSCD

采用固相萃取-高效液相色谱法同时测定复杂食品基质中的柠檬黄、日落黄、苋菜红、胭脂红、诱惑红、酸性红、赤藓红、亮蓝等8种合成色素的含量。样品经乙醇-乙腈-甲醇-氨水(3+3+3+1)混合液超声提取3次后,提取液采用ProElut PWA-2固相萃取柱净化,净化液在Agilent Eclipse XDB-C_(18)色谱柱上分离,以乙腈-0.02mol·L^(-1)乙酸铵溶液为流动相进行梯度洗脱,采用二极管阵列检测器,检测波长为254nm。8种合成色素的峰面积与其质量浓度在1.0~50.0mg·L^(-1)内呈线性关系,检出限(3S/N)在0.25~0.80μg·kg^(-1)之间。加标回收率为84.6%~99.0%,测定值的相对标准偏差(n=6)在1.4%~2.5%之间。