Superconvergence of mixed covolume method on quadrilateral grids for elliptic problems

This paper considers the mixed covolume method for the second-order elliptic equations over quadrilaterals.Superconvergence results are established in this paper on quadrilateral grids satisfying the h~2-parallelogram condition when the lowest-order Raviart-Thomas space is employed in the mixed covolume method.The authors prove O(h~2) accuracy between the approximate velocity or pressure and a suitable projection of the real velocity or pressure in the L~2 norm.Numerical experiments illustrating the theoretical results are provided.     

Maximum likelihood estimator of the parameter for a continuous one-parameter exponential family under the optimal ranked set sampling

This paper studies a maximum likelihood estimator (MLE) of the parameter for a continuous one-parameter exponential family under ranked set sampling (RSS). The authors first find the optimal RSS according to the character of the family, viz, arrange the RSS based on quasi complete and sufficient statistic of independent and identically distributed (iid) samples. Then under this RSS, some sufficient conditions for the existence and uniqueness of the MLE, which are easily used in practice, are obtained. Using these conditions, the existence and uniqueness of the MLEs of the parameters for some usual distributions in this family are proved. Numerical simulations for these distributions fully support the result from the above two step optimizations of the sampling and the estimation method.     

一种基于循环回归的推荐算法

提出了一种基于循环回归的推荐算法.首先,对原数据集中的评分数据及缺失值进行离散化处理,然后对离散化数据进行回归模型训练,此过程循环执行并最终建立推荐系统.在离散化阶段,对比不同的离散方法,并对它们的分类粒度开展研究.在模型训练阶段,讨论回归算法对于模型性能的影响.数值计算实验表明,本算法较之近年非常热门的SVDFeaute方法,能够产生更小的均方根误差,验证了算法的有效性.     

Selective susceptibility to nanosecond pulsed electric field (nsPEF) across different human cell types

Tumor ablation by nanosecond pulsed electric fields (nsPEF) is an emerging therapeutic modality. We compared nsPEF cytotoxicity for human cell lines of cancerous (IMR-32, Hep G2, HT-1080, and HPAF-II) and non-cancerous origin (BJ and MRC-5) under strictly controlled and identical conditions. Adherent cells were uniformly treated by 300-ns PEF (0–2000 pulses, 1.8 kV/cm, 50 Hz) on indium tin oxide-covered glass coverslips, using the same media and serum. Cell survival plotted against the number of pulses displayed three distinct regions (initial resistivity, logarithmic survival decline, and residual resistivity) for all tested cell types, but with differences in LD₅₀ spanning as much as nearly 80-fold. The non-cancerous cells were less sensitive than IMR-32 neuroblastoma cells but more vulnerable than the other cancers tested. The cytotoxic efficiency showed no apparent correlation with cell or nuclear size, cell morphology, metabolism level, or the extent of membrane disruption by nsPEF. Increasing pulse duration to 9 µs (0.75 kV/cm, 5 Hz) produced a different selectivity pattern, suggesting that manipulation of PEF parameters can, at least for certain cancers, overcome their resistance to nsPEF ablation. Identifying mechanisms and cell markers of differential nsPEF susceptibility will critically contribute to the proper choice and outcome of nsPEF ablation therapies.     

革新的效应特征及其价值评估

阐明了经济系统中的革新所引起的主要特征，利用两个Logistic方程之差来描述革新效应，确定了这类效应的主要特征参量，并以此为基础给出了革新价值评估方法，讨论了决策中的时间偏好在选择革新中的作用。     

Identification of AtSM34, a novel tonoplast intrinsic protein-interacting polypeptide expressed in response to osmotic stress in germinating seedlings

Aquaporins are implicated in a wide variety of plant physiological processes, although the mechanisms involved in their regulation are not fully understood. To gain further insight into the regulatory factors involved in this process, we used a yeast two-hybrid system to screen for potential binding partners to the Arabidopsis tonoplast intrinsic protein (TIP) AtTIP1;1. This was the first protein identified to be associated with high water permeability in vacuolar membranes from Arabidopsis thaliana. Using ...     

在数学教育中渗透创业教育的实践

创业教育能让学生把技能用到自主创业上，创造出更多的新产业和新岗位。数学是一门板为重要的基础学科，数学知识体系中蕴含着大量创业教育元素，可以在教学过程中渗透创业教育，主要做法是：改变数学教学观念，培养学生创业意识；优化数学教学模式，培养学生创业精神；开放数学教学形式，注重数学基本能力训练，培养创业技能。     

Letters from William Burnside to Robert Fricke: automorphic functions,and the emergence of the Burnside Problem

Two letters from William Burnside have recently been found in the Nachlass of Robert Fricke that contain instances of the Burnside Problem prior to its first publication. We present these letters as a whole to the public for the first time. We draw a picture of these two mathematicians and describe their activities leading to their correspondence. We thus gain an insight into their respective motivations, reactions, and attitudes, which may sharpen the current understanding of professional and social interactions of the mathematical community at the turn of the twentieth century. Dedicated to Heiko Harborth on the occasion of his seventieth birthday.     

关于Plya,Mordell的不等式

该文旨在改进数论中之Ｐｏｌｙａ，Ｍｏｒｄｅｌ的不等式